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10-Bit Digital Temperature Sensor (AD7416) and Four Single-Channel ADCs (AD7417/AD7418)
AD7416/AD7417/AD7418
FEATURES 10-Bit ADC with 15 s and 30 s Conversion Times Single and Four Single-Ended Analog Input Channels On-Chip Temperature Sensor: -40 C to +125 C On-Chip Track-and-Hold Overtemperature Indicator Automatic Power-Down at the End of a Conversion Wide Operating Supply Range: 2.7 V to 5.5 V I2C(R) Compatible Serial Interface Selectable Serial Bus Address Allows Connection of up to Eight AD7416/AD7417s to a Single Bus AD7416 Is a Superior Replacement for LM75 APPLICATIONS Data Acquisition with Ambient Temperature Monitoring Industrial Process Control Automotive Battery-Charging Applications Personal Computers GENERAL DESCRIPTION
A0 A1 A2 SERIAL BUS INTERFACE
FUNCTIONAL BLOCK DIAGRAMS
BAND GAP TEMPERATURE SENSOR
10-BIT ANALOG-DIGITAL CONVERTER TEMPERATURE VALUE REGISTER
AD7416
ADDRESS POINTER REGISTER
TOTI SETPOINT REGISTER THYST SETPOINT REGISTER CONFIGURATION REGISTER
SETPOINT COMPARATOR VDD FAULT QUEUE COUNTER OTI
GND SDA SCL
REFIN
VDD
The AD7417 and AD7418 are 10-bit, 4-channel and singlechannel ADCs with an on-chip temperature sensor that can operate from a single 2.7 V to 5.5 V power supply. The devices contain a 15 s successive approximation converter, a 5-channel multiplexer, a temperature sensor, a clock oscillator, a track-and-hold, and a reference (2.5 V). The AD7416 is a temperature-monitoring only device in an 8-lead package. The temperature sensor on the parts can be accessed via multiplexer Channel 0. When Channel 0 is selected and a conversion is initiated, the resulting ADC code at the end of the conversion gives a measurement of the ambient temperature (1C @ 25C). On-chip registers can be programmed with high and low temperature limits, and an open-drain overtemperature indicator (OTI) output is provided, which becomes active when a programmed limit is exceeded. A configuration register allows programming of the sense of the OTI output (active high or active low) and its operating mode (comparator or interrupt). A programmable fault queue counter allows the number of out-of-limit measurements that must occur before triggering the OTI output to be set to prevent spurious triggering of the OTI output in noisy environments. (continued on page 7)
OVERTEMP REG B TEMP SENSOR REF 2.5V AIN1 AIN2 AIN3 AIN4 VBALANCE MUX SAMPLING CAPACITOR + CHARGE DISTRIBUTION DAC
A>B A DATA OUT
OTI
CLOCK
CONTROL LOGIC
SCL I2C INTERFACE SDA
AD7417
NC NC GND NC = NO CONNECT
CONVST
A0
A1
A2
VDD
REFIN
OVERTEMP REG B
A>B A
OTI
TEMP SENSOR
REF 2.5V
CHARGE DISTRIBUTION DAC
DATA OUT
AIN1
MUX CLOCK SAMPLING CAPACITOR + CONTROL LOGIC I2C INTERFACE
SCL
SDA
REV. G
GND
VBALANCE CONVST
AD7418
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 www.analog.com Fax: 781/326-8703 (c) 2004 Analog Devices, Inc. All rights reserved.
AD7416/AD7417/AD7418
AD7417/AD7418-SPECIFICATIONS
Parameter DC ACCURACY Resolution Minimum Resolution for Which No Missing Codes Are Guaranteed Relative Accuracy2 Differential Nonlinearity2 Gain Error2 Gain Error Match2 Offset Error2 Offset Error Match ANALOG INPUTS Input Voltage Range Input Leakage Current3 Input Capacitance TEMPERATURE SENSOR1 Measurement Error Ambient Temperature 25C TMIN to TMAX Temperature Resolution CONVERSION RATE Track-and-Hold Acquisition Time4 Conversion Time Temperature Sensor Channels 1 to 4 REFERENCE INPUT5, 6 REFIN Input Voltage Range6 Input Impedance Input Capacitance ON-CHIP REFERENCE Reference Error6 Temperature Coefficient6 DIGITAL INPUTS Input High Voltage, VIH Input Low Voltage, VIL Input Leakage Current DIGITAL OUTPUTS Output Low Voltage, VOL Output High Current POWER REQUIREMENTS VDD IDD Normal Operation Power-Down Auto Power-Down Mode 10 SPS Throughput Rate 1 kSPS Throughput Rate 10 kSPS Throughput Rate Power-Down A Version 10 10 1 1 3 10 0.6 4 0.7 VREF 0 1 10 B Version1 10 10 1 1 3 10 0.6 4 0.7 VREF 0 1 10
(VDD = 2.7 V to 5.5 V, GND = 0 V, REFIN = 2.5 V, unless otherwise noted.) Unit Bits Bits LSB max LSB max LSB max LSB max LSB max LSB max LSB max V max V min A max pF max Test Conditions/Comments Any Channel.
This Specification Is Typical for VDD of 3.6 V to 5.5 V. This Specification Is Typical for VDD of 3.6 V to 5.5 V. External Reference. Internal Reference. AD7417 Only. AD7417 Only.
2 3 1/4 400 30 15 2.625 2.375 40 10 25 80 VDD x 0.7 VDD x 0.3 1 0.4 1 5.5 2.7 600 1 6 60 600 3
1 2 1/4 400 30 15 2.625 2.375 40 10 25 80 VDD x 0.7 VDD x 0.3 1 0.4 1 5.5 2.7 600 1 6 60 600 3 -2-
C max C max C/LSB ns max s max s max V max V min k min pF max mV max ppm/C typ V min V max A max V max A max V max V min A max A max W typ W typ W typ W max IOL = 3 mA. VOH = 5 V. For Specified Performance. Logic Inputs = 0 V or VDD. 50 nA Typically. VDD = 3 V. See Operating Modes. Source Impedance < 10 . Typically 27 s. Typically 10 s. 2.5 V + 5%. 2.5 V - 5%.
Nominal 2.5 V.
Typically 0.15 W. REV. G
AD7416/AD7417/AD7418
NOTES 1 B Version applies to AD7417 only with temperature range of -40C to +85C. A Version temperature range is -40C to +125C. For VDD = 2.7 V, TA = 85C max and temperature sensor measurement error = 3C. 2 See Terminology. 3 Refers to the input current when the part is not converting. Primarily due to reverse leakage current in the ESD protection diodes. 4 Sample tested during initial release and after any redesign or process change that may affect this parameter. 5 On-chip reference shuts down when external reference is applied. 6 The accuracy of the temperature sensor is affected by reference tolerance. The relationship between the two is explained in the Temperature Sensor section. Specifications subject to change without notice.
AD7416-SPECIFICATIONS
Parameter
(VDD = 2.7 V to 5.5 V, GND = 0 V, REFIN = 2.5 V, unless otherwise noted.) Min Typ Max 2.0 3.0 Unit C C Bits s s ms mA A A C C V V A A pF V A ns V s ns ns ns ns ns Test Conditions/Comments TA = -25C to +100C (VDD = 3 V min)1 TA = -40C to +125C (VDD = 3 V min)1
TEMPERATURE SENSOR AND ADC Accuracy
Resolution Temperature Conversion Time Update Rate, tR OTI Delay Supply Current
10 40 400 1 x tR 350 0.2 80 75 VDD x 0.7 -0.3 +0.005 -0.005 20 6 x tR 1.0 600 1.5
Depends on Fault Queue Setting I2C Active I2C Inactive Shutdown Mode
TOTI Default Temperature THYST Default Temperature DIGITAL INPUTS Input High Voltage, VIH Input Low Voltage, VIL Input High Current, IIH Input Low Current, IIL Input Capacitance, CIN DIGITAL OUTPUTS Output Low Voltage, VOL Output High Current Output Fall Time, tf OS Output Low Voltage, VOL AC ELECTRICAL CHARACTERISTICS2 Serial Clock Period, t1 Data In Setup Time to SCL High, t2 Data Out Stable after SCL Low, t3 SDA Low Setup Time to SCL Low (Start Condition), t4 SDA High Hold Time after SCL High (Stop Condition), t5 SDA and SCL Fall Time, t6 2.5 50 0 50 50
VDD + 0.5 VDD x 0.3 +1.0 -1.0
VIN = 5 V VIN = 0 V All Digital Inputs IOL = 3 mA VOH = 5 V CL = 400 pF, IO = 3 mA IOUT = 4 mA AD7416/AD7417/AD7418 See Figure 1 See Figure 1 See Figure 1 See Figure 1 See Figure 1 See Figure 1
0.4 1 250 0.8
300
NOTES 1 For VDD = 2.7 V to 3 V, T A max = 85C and accuracy = 3C. 2 Sample tested during initial release and after any redesign or process change that may affect this parameter. Specifications subject to change without notice.
t1
SCL
t4
SDA DATA IN
t2
t5
t3
SDA DATA OUT
t6
Figure 1. Diagram for Serial Bus Timing
REV. G
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AD7416/AD7417/AD7418
AD7417 PIN FUNCTION DESCRIPTION
Pin No. 1, 16 2 3 4
Mnemonic NC SDA SCL OTI
Description No Connection. Do not connect anything to this pin. Digital I/O. Serial bus bidirectional data. Push-pull output. Digital Input. Serial bus clock. This is a logic output. The overtemperature indicator (OTI) is set if the result of a conversion on Channel 0 (temperature sensor) is greater than an 8-bit word in the overtemperature register (OTR). The signal is reset at the end of a serial read operation. Open-drain output. Reference Input. An external 2.5 V reference can be connected to the AD7417 at this pin. To enable the on-chip reference, the REFIN pin should be tied to GND. If an external reference is connected to the AD7417, the internal reference will shut down. Ground reference for track-and-hold, comparator and capacitor DAC, and digital circuitry. Analog Input Channels. The AD7417 has four analog input channels. The input channels are single-ended with respect to GND. The input channels can convert voltage signals in the range 0 V to VREF. A channel is selected by writing to the configuration register of the AD7417. (See Control Byte section.) Digital Input. The highest programmable bit of the serial bus address. Digital Input. The middle programmable bit of the serial bus address. Digital Input. The lowest programmable bit of the serial bus address. Positive Supply Voltage, 2.7 V to 5.5 V. Logic Input Signal. Convert start signal. The rising edge of this signal fully powers up the part. The power-up time for the part is 4 s. If the CONVST pulse is greater than 4 s, the falling edge of CONVST places the track-and-hold mode into hold mode and initiates a conversion. If the pulse is less than 4 s, an internal timer ensures that the track-and-hold does not go into hold and conversion is not initiated until the power-up time has elapsed. The track-and-hold goes into track mode again at the end of conversion. (See Operating Mode section.)
5
REFIN
6 7-10
GND AIN1 to AIN4
11 12 13 14 15
A2 A1 A0 VDD CONVST
AD7417 PIN CONFIGURATION SOIC/TSSOP
NC 1 SDA 2 SCL 3 OTI 4
16 NC 15 CONVST 14 VDD
AD7417
13 A0
TOP VIEW REFIN 5 (Not to Scale) 12 A1 GND 6 AIN1 7 AIN2 8
11 A2 10 AIN4 9
AIN3
NC = NO CONNECT
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AD7416/AD7417/AD7418
AD7416 PIN FUNCTION DESCRIPTION
Pin No. 1 2 3
Mnemonic SDA SCL OTI
Description Digital I/O. Serial bus bidirectional data. Push-pull output. Digital Input. Serial bus clock. This is a logic output. The OTI is set if the result of a conversion on Channel 0 (temperature sensor) is greater that an 8-bit word in the OTR. The signal is reset at the end of a serial read operation. Opendrain output. Ground reference for track-and-hold, comparator and capacitor DAC, and digital circuitry. Digital Input. The highest programmable bit of the serial bus address. Digital Input. The middle programmable bit of the serial bus address. Digital Input. The lowest programmable bit of the serial bus address. Positive Supply Voltage, 2.7 V to 5.5 V.
AD7418 PIN FUNCTION DESCRIPTION
4 5 6 7 8
GND A2 A1 A0 VDD
Pin No. 1 2 3
Mnemonic SDA SCL OTI
Description Digital I/O. Serial bus bidirectional data. Push-pull output. Digital Input. Serial bus clock. This is a logic output. The OTI is set if the result of a conversion on Channel 0 (temperature sensor) is greater that an 8-bit word in the OTR. The signal is reset at the end of a serial read operation. Opendrain output. Ground reference for track-and-hold, comparator and capacitor DAC, and digital circuitry. Analog Input Channel. The input channel is single-ended with respect to GND. The input channel can convert voltage signals in the range 0 V to VREF. The analog input channel is selected by writing to the configuration register of the AD7418 and choosing Channel 4. (See Control Byte section.) Reference Input. An external 2.5 V reference can be connected to the AD7418 at this pin. To enable the on-chip reference, the REFIN pin should be tied to GND. If an external reference is connected to the AD7418, the internal reference will shut down. Positive Supply Voltage, 2.7 V to 5.5 V. Logic Input Signal. Convert start signal. The rising edge of this signal fully powers up the part. The power-up time for the part is 4 s. If the CONVST pulse is greater than 4 s, the falling edge of CONVST places the track-and-hold mode into hold mode and initiates a conversion. If the pulse is less than 4 s, an internal timer ensures that the track-and-hold does not go into hold and conversion is not initiated until the power-up time has elapsed. The track-and-hold goes into track mode again at the end of conversion. (See Operating Mode section.)
4 5
GND AIN
6
REFIN
7 8
VDD CONVST
AD7416 PIN CONFIGURATION SOIC/MSOP
AD7418 PIN CONFIGURATION SOIC/MSOP
CONVST
SDA 1 SCL 2
8
VDD A0
SDA 1 SCL 2
8
AD7416
7
TOP VIEW OTI 3 (Not to Scale) 6 A1 GND 4
5
VDD TOP VIEW OTI 3 (Not to Scale) 6 REFIN
7 5
AD7418
A2
GND 4
AIN
REV. G
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AD7416/AD7417/AD7418
ABSOLUTE MAXIMUM RATINGS 1
(TA = 25C, unless otherwise noted.) VDD to AGND . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 V to +7 V VDD to DGND . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 V to +7 V Analog Input Voltage to AGND AIN1 to AIN4 . . . . . . . . . . . . . . . . . . . -0.3 V to VDD + 0.3 V Reference Input Voltage to AGND2 . . -0.3 V to VDD + 0.3 V Digital Input Voltage to DGND . . . . . -0.3 V to VDD + 0.3 V Digital Output Voltage to DGND . . . . -0.3 V to VDD + 0.3 V Operating Temperature Range A Version . . . . . . . . . . . . . . . . . . . . . . . . . -40C to +125C B Version . . . . . . . . . . . . . . . . . . . . . . . . . . -40C to +85C Storage Temperature Range . . . . . . . . . . . . -65C to +150C Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . 150C TSSOP, Power Dissipation . . . . . . . . . . . . . . . . . . . . 450 mW JA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 120C/W Lead Temperature, Soldering . . . . . . . . . . . . . . . . . . 260C Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . 215C Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . . 220C 16-Lead SOIC Package, Power Dissipation . . . . . . . . 450 mW JA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 100C/W Lead Temperature, Soldering Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . 215C Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . . 220C
8-Lead SOIC Package, Power Dissipation . . . . . . . . . 450 mW JA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 157C/W Lead Temperature, Soldering Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . 215C Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . . 220C MSOP Package, Power Dissipation . . . . . . . . . . . . . . 450 mW JA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 206C/W Lead Temperature, Soldering Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . 215C Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . . 220C
NOTES 1 Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those listed in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. 2 If the reference input voltage is likely to exceed V DD by more than 0.3 V (e.g., during power-up) and the reference is capable of supplying 30 mA or more, it is recommended to use a clamping diode between the REF IN pin and VDD pin. The diagram below shows how the diode should be connected.
REFIN VDD
BAT81
AD7417
CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD7416/AD7417/AD7418 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
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AD7416/AD7417/AD7418
ORDERING GUIDE
Model AD7416ACHIPS AD7416AR AD7416AR-REEL AD7416AR-REEL7 AD7416ARZ* AD7416ARZ-REEL* AD7416ARZ-REEL7* AD7416ARM AD7416ARM-REEL AD7416ARM-REEL7 AD7416ARMZ* AD7416ARMZ-REEL* AD7416ARMZ-REEL7* AD7417ACHIPS AD7417AR AD7417AR-REEL AD7417AR-REEL7 AD7417ARU AD7417ARU-REEL AD7417ARU-REEL7 AD7417BR AD7417BR-REEL AD7417BR-REEL7 AD7418ACHIPS AD7418AR AD7418AR-REEL AD7418AR-REEL7 AD7418ARM AD7418ARM-REEL AD7418ARM-REEL7 AD7418ARUZ* AD7418ARUZ-REEL* AD7418ARUZ-REEL7* EVAL-AD7416/AD7417/ AD7418EB
*Pb-Free Part
Temperature Range -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +85C -40C to +85C -40C to +85C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C
Temperature Error 2C 2C 2C 2C 2C 2C 2C 2C 2C 2C 2C 2C 2C 2C 2C 2C 2C 2C 1C 1C 1C 2C 2C 2C 2C 2C 2C 2C 2C 2C
Package Description Die 8-Lead Standard Small Outline Package (SOIC) 8-Lead Standard Small Outline Package (SOIC) 8-Lead Standard Small Outline Package (SOIC) 8-Lead Standard Small Outline Package (SOIC) 8-Lead Standard Small Outline Package (SOIC) 8-Lead Standard Small Outline Package (SOIC) 8-Lead Micro Small Outline Package (MSOP) 8-Lead Micro Small Outline Package (MSOP) 8-Lead Micro Small Outline Package (MSOP) 8-Lead Micro Small Outline Package (MSOP) 8-Lead Micro Small Outline Package (MSOP) 8-Lead Micro Small Outline Package (MSOP) Die 16-Lead Standard Small Outline Package (SOIC) 16-Lead Standard Small Outline Package (SOIC) 16-Lead Standard Small Outline Package (SOIC) 16-Lead Thin Shrink Small Outline Package (TSSOP) 16-Lead Thin Shrink Small Outline Package (TSSOP) 16-Lead Thin Shrink Small Outline Package (TSSOP) 16-Lead Standard Small Outline Package (SOIC) 16-Lead Standard Small Outline Package (SOIC) 16-Lead Standard Small Outline Package (SOIC) Die 8-Lead Standard Small Outline Package (SOIC) 8-Lead Standard Small Outline Package (SOIC) 8-Lead Standard Small Outline Package (SOIC) 8-Lead Micro Small Outline Package (MSOP) 8-Lead Micro Small Outline Package (MSOP) 8-Lead Micro Small Outline Package (MSOP) 16-Lead Thin Shrink Small Outline Package (TSSOP) 16-Lead Thin Shrink Small Outline Package (TSSOP) 16-Lead Thin Shrink Small Outline Package (TSSOP) Evaluation Board
Branding
Package Option RN-8 RN-8 RN-8 RN-8 RN-8 RN-8 RM-8 RM-8 RM-8 RM-8 RM-8 RM-8 RN-16 RN-16 RN-16 RU-16 RU-16 RU-16 RN-16 RN-16 RN-16 RN-8 RN-8 RN-8 RM-8 RM-8 RM-8 RU-16 RU-16 RU-16
C6A C6A C6A C6A C6A C6A
C7A C7A C7A
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AD7416/AD7417/AD7418
(continued from page 1) An I2C compatible serial interface allows the AD7416/AD7417/ AD7418 registers to be written to and read back. The three LSBs of the AD7416/AD7417's serial bus address can be selected, which allows up to eight AD7416/AD7417s to be connected to a single bus. The AD7417 is available in a narrow body, 0.15'', 16-lead, small outline IC (SOIC) and in a 16-lead, thin shrink, small outline package (TSSOP). The AD7416 and AD7418 are available in 8-lead SOIC and MSOP packages.
PRODUCT HIGHLIGHTS
situations where a change in the selected input channel takes place or where there is a step input change on the input voltage applied to the selected AIN input of the AD7417 or AD7418. It means that the user must wait for the duration of the track-andhold acquisition time after the end of conversion or after a channel change/step input change to AIN before starting another conversion, to ensure that the part operates to specification.
CIRCUIT INFORMATION
1. The AD7416/AD7417/AD7418 have an on-chip temperature sensor that allows an accurate measurement of the ambient temperature ( 1C @ 25C, 2C overtemperature) to be made. The measurable temperature range is -40C to +125C. An overtemperature indicator is implemented by carrying out a digital comparison of the ADC code for Channel 0 (temperature sensor) with the contents of the on-chip overtemperature register. 2. The AD7417 offers a space-saving 10-bit A/D solution with four external voltage input channels, an on-chip temperature sensor, an on-chip reference, and clock oscillator. 3. The automatic power-down feature enables the AD7416/ AD7417/AD7418 to achieve superior power performance. At slower throughput rates, the part can be programmed to operate in a low power shutdown mode, allowing further savings in power consumption.
TERMINOLOGY Relative Accuracy
The AD7417 and AD7418 are single-channel and four-channel, 15 s conversion time, 10-bit ADCs with on-chip temperature sensor, reference, and serial interface logic functions on a single chip. The AD7416 has no analog input channel and is intended for temperature measurement only. The ADC section consists of a conventional successive approximation converter based around a capacitor DAC. The AD7416, AD7417, and AD7418 are capable of running on a 2.7 V to 5.5 V power supply, and the AD7417 and AD7418 accept an analog input range of 0 V to +VREF. The on-chip temperature sensor allows an accurate measurement of the ambient device temperature to be made. The working measurement range of the temperature sensor is -40C to +125C. The parts require a 2.5 V reference that can be provided from the part's own internal reference or from an external reference source.
CONVERTER DETAILS
Relative accuracy or endpoint nonlinearity is the maximum deviation from a straight line passing through the endpoints of the ADC transfer function.
Differential Nonlinearity
This is the difference between the measured and the ideal 1 LSB change between any two adjacent codes in the ADC.
Offset Error
This is the deviation of the first code transition (0000 . . . 000) to (0000 . . . 001) from the ideal, i.e., GND + 1 LSB.
Offset Error Match
Conversion is initiated on the AD7417/AD7418 by pulsing the CONVST input. The conversion clock for the part is internally generated so no external clock is required except when reading from and writing to the serial port. The on-chip track-and-hold goes from track to hold mode and the conversion sequence is started on the falling edge of the CONVST signal. A conversion is also initiated in the automatic conversion mode every time a read or write operation to the AD7416/AD7417/AD7418 takes place. In this case, the internal clock oscillator (which runs the automatic conversion sequence) is restarted at the end of the read or write operation. The track-and-hold goes into hold approximately 3 s after the read or write operation is complete and a conversion is then initiated. The result of the conversion is available either 15 s or 30 s later, depending on whether an analog input channel or the temperature sensor is selected. The track-and-hold acquisition time of the AD7417/AD7418 is 400 ns. A temperature measurement is made by selecting the Channel 0 of the on-chip mux and carrying out a conversion on this channel. A conversion on Channel 0 takes 30 s to complete. Temperature measurement is explained in the Temperature Measurement section of this data sheet. The on-chip reference is not available to the user, but REFIN can be overdriven by an external reference source (2.5 V only). All unused analog inputs should be tied to a voltage within the nominal analog input range to avoid noise pickup. For minimum power consumption, the unused analog inputs should be tied to GND.
This is the difference in offset error between any two channels.
Gain Error
This is the deviation of the last code transition (1111 . . . 110) to (1111 . . . 111) from the ideal, i.e., VREF - 1 LSB, after the offset error has been adjusted out.
Gain Error Match
This is the difference in gain error between any two channels.
Track-and-Hold Acquisition Time
Track-and-hold acquisition time is the time required for the output of the track-and-hold amplifier to reach its final value, within 1/2 LSB, after the end of conversion (the point at which the track-and-hold returns to track mode). It also applies to
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AD7416/AD7417/AD7418
TYPICAL CONNECTION DIAGRAM
1.2V
SUPPLY 2.7V TO 5.5V
1.2V
VDD 0V TO 2.5V INPUT AIN1 AIN2 AIN3 AIN4
SCL SDA
CONVST OTI C/ P
AD7417
GND REFIN OPTIONAL EXTERNAL REFERENCE A0 A1 A2
Figure 4. On-Chip Reference
TEMPERATURE MEASUREMENT
AD780/ REF-192
10 F FOR EXTERNAL REFERENCE
Figure 2. Typical Connection Diagram
ANALOG INPUTS
A common method of measuring temperature is to exploit the negative temperature coefficient of a diode, or the base-emitter voltage of a transistor, operated at a constant current. Unfortunately, this technique requires calibration to null out the effect of the absolute value of VBE, which varies from device to device. The technique used in the AD7416/AD7417/AD7418 is to measure the current change in VBE when the device is operated at two different currents. This is given by VBE = KT / q x 1n (N ) where: K is Boltzmann's constant. q is the charge on the electron (1.6 x 10-19 Coulombs). T is the absolute temperature in Kelvins. N is the ratio of the two currents.
VDD I N I
Figure 3 shows an equivalent circuit of the analog input structure of the AD7417 and AD7418. The two diodes, D1 and D2, provide ESD protection for the analog inputs. Care must be taken to ensure that the analog input signal never exceeds the supply rails by more than 200 mV. This will cause these diodes to become forward-biased and start conducting current into the substrate. The maximum current these diodes can conduct without causing irreversible damage to the part is 20 mA. The capacitor C2 in Figure 3 is typically about 4 pF and can primarily be attributed to pin capacitance. The resistor R1 is a lumped component made up of the on resistance of a multiplexer and a switch. This resistor is typically about 1 k. The capacitor C1 is the ADC sampling capacitor and has a capacitance of 3 pF.
VDD
D1 AIN C2 4pF D2
R1 1k
C1 3pF VBALANCE
SENSING TRANSISTOR SENSING TRANSISTOR
CONVERT PHASE - SWITCH OPEN TRACK PHASE - SWITCH CLOSED
Figure 3. Equivalent Analog Input Circuit
ON-CHIP REFERENCE
Figure 5. Temperature Measurement Technique
The AD7416/AD7417/AD7418 has an on-chip 1.2 V band gap reference that is gained up by a switched capacitor amplifier to give an output of 2.5 V. The amplifier is only powered up at the REV. G -9-
+
10 F
0.1 F
2-WIRE SERIAL INTERFACE
SW1
26k
2.5V
24k
+
Figure 2 shows a typical connection diagram for the AD7417. Using the A0, A1, and A2 pins allows the user to select from up to eight AD7417s on the same serial bus, if desired. An external 2.5 V reference can be connected at the REFIN pin. If an external reference is used, a 10 F capacitor should be connected between REFIN and GND. SDA and SCL form the 2-wire I2C compatible interface. For applications where power consumption is of concern, the automatic power-down at the end of a conversion should be used to improve power performance. See Operating Modes section of this data sheet.
start of the conversion phase and is powered down at the end of the conversion. The on-chip reference is selected by connecting the REFIN pin to analog ground. This causes SW1 (see Figure 4) to open and the reference amplifier to power up during a conversion. Therefore, the on-chip reference is not available externally. An external 2.5 V reference can be connected to the REFIN pin. This has the effect of shutting down the on-chip reference circuitry.
REFIN EXTERNAL REFERENCE DETECT
BUFFER
VOUT TO ADC VOUT
AD7416/AD7417/AD7418
Figure 5 shows the method the AD7416/AD7417/AD7418 uses to measure the device temperature. To measure VBE, the sensor (substrate transistor) is switched between operating currents of I and N x I. The resulting waveform is passed through a chopper-stabilized amplifier that performs the functions of amplification and rectification of the waveform to produce a dc voltage proportional to VBE. This voltage is measured by the ADC to give a temperature output in 10-bit twos complement form. The temperature resolution of the ADC is 0.25C, which corresponds to 1 LSB of the ADC. The ADC can theoretically measure a temperature span of 255C; the guaranteed temperature range is -40C to +125C. The result of the conversion is stored in the Temperature Value Register (00h) as a 16-bit word. The 10 MSBs of this word store the temperature measurement (see Table III and Table IV). The temperature conversion formula using the 10 MSBs of the Temperature Value Register is 1. Positive Temperature = ADC Code/4 2. Negative Temperature = (ADC Code* - 512)/4 *MSB is removed from the ADC Code.
INTERNAL REGISTER STRUCTURE ADDRESS POINTER REGISTER
The Address Pointer Register is an 8-bit register that stores an address that points to one of the six data registers. The first data byte of every serial write operation to the AD7416/AD7417/ AD7418 is the address of one of the data registers, which is stored in the Address Pointer Register, and selects the data register to which subsequent data bytes are written. Only the three LSBs of this register are used to select a data register.
Table I. Address Pointer Register
P7* 0
P6* 0
P5* 0
P4* 0
P3* 0
P2
P1
P0
Register Select
*P3 to P7 must be set to 0.
Table II. Register Addresses
P2 0 0 0 0 1 1
P1 0 0 1 1 0 0
P0 0 1 0 1 0 1
Registers Temperature Value (Read-Only) Config Register (Read/Write) THYST (Read/Write) TOTI ADC (AD7417/AD7418 Only) Config2 (AD7417/AD7418 Only)
The AD7417/AD7418 has seven internal registers, as shown in Figure 6. Six of these are data registers and one is an Address Pointer Register. The AD7416 has five internal registers (the ADC and Config2 Registers are not applicable to the AD7416).
TEMPERATURE VALUE REGISTER (READ-ONLY ADDRESS 00h)
TEMPERATURE VALUE REGISTER (ADDRESS 00h)
The Temperature Value Register is a 16-bit, read-only register whose 10 MSBs store the temperature reading from the ADC in 10-bit twos complement format. Bits 5 to 0 are unused.
Table III. Temperature Value Register
D15 D14
CONFIGURATION REGISTER (READ/WRITE ADDRESS 01h)
D13 B7
D12 B6
D11 D10 B5 B4
D9 B3
D8 B2
D7 B1
D6 LSB
MSB B8
THYST SETPOINT REGISTER (READ/WRITE ADDRESS 02h) TOTI SETPOINT REGISTER (READ/WRITE ADDRESS 03h) ADDRESS POINTER REGISTER (SELECTS DATA REGISTER FOR READ/WRITE) ADDRESS CONFIG2 REGISTER (READ/WRITE ADDRESS 05h) ADC REGISTER (READ-ONLY ADDRESS 04h) DATA
The temperature data format is shown in Table IV. This shows the full theoretical range of the ADC from -128C to +127C, but in practice, the temperature measurement range is limited to the operating temperature range of the device.
Table IV. Temperature Data Format
Temperature -128C -125C -100C -75C -50C -25C -0.25C 0C +0.25C +10C +25C +50C +75C +100C +125C +127C
Digital Output 10 0000 0000 10 0000 1100 10 0111 0000 10 1101 0100 11 0011 1000 11 1001 1100 11 1111 1111 00 0000 0000 00 0000 0001 00 0010 1000 00 0110 0100 00 1100 1000 01 0010 1100 01 1001 0000 01 1111 0100 01 1111 1100
SERIAL BUS INTERFACE
SDA SCL
Figure 6. AD7417/AD7418 Register Structure
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AD7416/AD7417/AD7418
CONFIGURATION REGISTER (ADDRESS 01h) ADC VALUE REGISTER (ADDRESS 04h)
The Configuration Register is an 8-bit, read/write register that is used to set the operating modes of the AD7416/AD7417/ AD7418. Bits D7 to D5 control the channel selection as outlined in Table VI. These bits should always be 0, 0, 0 for the AD7416. Bits D4 and D3 are used to set the length of the fault queue. D2 sets the sense of the OTI output. D1 selects the comparator or interrupt mode of operation, and D0 = 1 selects the shutdown mode (Default D0 = 0).
Table V. Configuration Register
The ADC Value Register is a 16-bit, read-only register whose 10 MSBs store the value produced by the ADC in binary format. Bits 5 to 0 are unused. Table IX shows the ADC Value Register with 10 MSBs containing the ADC conversion request.
Table IX. ADC Value Register
D15 MSB
D14 D13 D12 B8 B7 B6
D11 B5
D10 B4
D9 B3
D8 B2
D7 B1
D6 LSB
D7
D6
D5
D4
D3
D2 OTI Polarity
D1 Cmp/ Int
D0 Shutdown
ADC Transfer Function
Channel Selection
Fault Queue
The designed code transitions occur at successive integer LSB values (i.e., 1 LSB, 2 LSB, and so on). The LSB size = VREF/ 1024. The ideal transfer function characteristic for the AD7417 and AD7418 ADC is shown in Figure 7.
The AD7416 contains a temperature-only channel, the AD7417 has four analog input channels and a temperature channel, and the AD7418 has two channels, a temperature channel, and an analog input channel. The temperature channel address for all parts is the same, CH0. The address for the analog input channel on the AD7418 is CH4. Table VI outlines the channel selection on the parts, while Table VII shows the fault queue settings. D1 and D2 are explained in the OTI Output section.
Table VI. Channel Selection
111...111 111...110
ADC CODE
111...000 1LSB = V REF/1024 011...111
000...010 000...001 000...000 0V 1/2LSB +VREF - 1LSB ANALOG INPUT
D7 0 0 0 0 1
D6 0 0 1 1 0
D5 0 1 0 1 0
Channel Selection Temperature Sensor (All Parts) AIN1 (AD7417 Only) AIN2 (AD7417 Only) AIN3 (AD7417 Only) AIN4 (AD7417) and AIN (AD7418)
Figure 7. Ideal Transfer Function Characteristic for the AD7417/AD7418
CONFIG2 REGISTER (ADDRESS 05h)
Table VII. Fault Queue Settings
D4 0 0 1 1
D3 0 1 0 1
Number of Faults 1 (Power-Up Default) 2 4 6
A second configuration register is included in the AD7417/ AD7418 for the functionality of the CONVST pin. It is an 8-bit register with Bits D5 to D0 being left at 0. Bit D7 determines whether the AD7417/AD7418 should be operated in its default mode (D7 = 0), performing conversions every 355 s or in its CONVST pin mode (D7 = 1), where conversions will start only when the CONVST pin is used. Bit 6 contains the Test 1 Bit. When this bit is 0, the I2C filters are enabled (default). A 1 disables the filters.
Table X. CONFIG2 Register
THYST SETPOINT REGISTER (ADDRESS 02h)
D7 Conversion Mode
D6
D5
D4 0
D3 0
D2 0
D1 0
D0 0
The THYST Setpoint Register is a 16-bit, read/write register whose nine MSBs store the THYST setpoint in twos complement format equivalent to the nine MSBs of the Temperature Value Register. Bits 6 to 0 are unused.
TOTI SETPOINT REGISTER (ADDRESS 03h)
Test 1 0
SERIAL BUS INTERFACE
The TOTI Setpoint Register is a 16-bit, read/write register whose nine MSBs store the TOTI setpoint in twos complement format equivalent to the nine MSBs of the Temperature Value Register. Bits 6 to 0 are unused.
Table VIII. Setpoint Registers
Control of the AD7416/AD7417/AD7418 is carried out via the I2C compatible serial bus. The AD7416/AD7417/AD7418 is connected to this bus as a slave device, under the control of a master device, e.g., the processor.
SERIAL BUS ADDRESS
D15 MSB
D14 B7
D13 B6
D12 B5
D11 B4
D10 B3
D9 B2
D8 B1
D7 LSB
As with all I2C compatible devices, the AD7416/AD7417/AD7418 have a 7-bit serial address. The four MSBs of this address for the AD7416 are set to 1001; the AD7417 are set to 0101, while the three LSBs can be set by the user by connecting the A2 to A0 pins to either VDD or GND. By giving them different addresses, up to eight AD7416/AD7417s can be connected to a single serial bus, -11-
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AD7416/AD7417/AD7418
or the addresses can be set to avoid conflicts with other devices on the bus. The four MSBs of this address for the AD7418 are set to 0101, while the three LSBs are all set to zero. If a serial communication occurs during a conversion operation, the conversion will stop and will restart after the communication. The serial bus protocol operates as follows: 1. The master initiates data transfer by establishing a start condition, defined as a high-to-low transition on the serial data line, SDA, while the serial clock line, SCL, remains high. This indicates that an address/data stream will follow. All slave peripherals connected to the serial bus respond to the 7-bit address (MSB first) plus an R/W bit, which determines the direction of the data transfer, i.e., whether data will be written to or read from the slave device. The peripheral whose address corresponds to the transmitted address responds by pulling the data line low during the low period before the ninth clock pulse, known as the Acknowledge bit. All other devices on the bus now remain idle while the selected device waits for data to be read from or written to it. If the R/W bit is a 0, then the master will write to the slave device. If the R/W bit is a 1, then the master will read from the slave device. 2. Data is sent over the serial bus in sequences of nine clock pulses, eight bits of data followed by an Acknowledge bit from the receiver of data. Transitions on the data line must occur during the low period of the clock signal and remain stable during the high period, since a low-to-high transition when the clock is high may be interpreted as a stop signal. 3. When all data bytes have been read or written, stop conditions are established. In write mode, the master will pull the data line high during the 10th clock pulse to assert a stop condition. In read mode, the master device will pull the data
1 SCL 9 1
line high during the low period before the 9th clock pulse. This is known as No Acknowledge. The master will then take the data line low during the low period before the 10th clock pulse, then high during the 10th clock pulse to assert a stop condition. Any number of bytes of data may be transferred over the serial bus in one operation, but it is not possible to mix read and write in one operation because the type of operation is determined at the beginning and cannot subsequently be changed without starting a new operation.
WRITING TO THE AD7416/AD7417/AD7418
Depending on the register being written to, there are three different writes for the AD7416/AD7417/AD7418. 1. Writing to the Address Pointer Register for a subsequent read. In order to read data from a particular register, the Address Pointer Register must contain the address of that register. If it does not, the correct address must be written to the Address Pointer Register by performing a single-byte write operation, as shown in Figure 8. The write operation consists of the serial bus address followed by the address pointer byte. No data is written to any of the data registers. 2. Writing a single byte of data to the configuration registers or to the TOTI, THYST registers. The Configuration Register is an 8-bit register, so only one byte of data can be written to it. If only 8-bit temperature comparisons are required, the temperature LSB can be ignored in TOTI and THYST, and only eight bits need be written to the TOTI and THYST registers. Writing a single byte of data to one of these registers consists of the serial bus address, the data register address written to
9
SDA START BY MASTER
1
0
0
1
A2
A1
A0
R/W ACK. BY AD7416
P7
P6
P5
P4
P3
P2
P1
P0 ACK. BY AD7416 STOP BY MASTER
FRAME 1 SERIAL BUS ADDRESS BYTE
FRAME 2 ADDRESS POINTER REGISTER BYTE
Figure 8. Writing to the Address Pointer Register to Select a Data Register for a Subsequent Read Operation
1 SCL 9 1 9
SDA START BY MASTER
1
0
0
1
A2
A1
A0
R/W ACK. BY AD7416
P7
P6
P5
P4
P3
P2
P1
P0 ACK. BY AD7416
FRAME 1 SERIAL BUS ADDRESS BYTE 1 SCL (CONTINUED)
FRAME 2 ADDRESS POINTER REGISTER BYTE 9
SDA (CONTINUED)
D7
D6
D5
D4
D3
D2
D1
D0 ACK. BY AD7416 STOP BY MASTER
FRAME 3 DATA BYTE
Figure 9. Writing to the Address Pointer Register Followed by a Single Byte of Data to the Selected Data Register
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AD7416/AD7417/AD7418
the Address Pointer Register, followed by the data byte written to the selected data register. This is illustrated in Figure 9. 3. Writing two bytes of data to the TOTI or THYST Register. If 9-bit resolution is required for the temperature setpoints, two bytes of data must be written to the TOTI and THYST registers. This consists of the serial bus address, the register address written to the address pointer register, followed by two data bytes written to the selected data register. This is illustrated in Figure 10.
READING DATA FROM THE AD7416/AD7417/AD7418
Reading data from the AD7416/AD7417/AD7418 is a one or two byte operation. Reading back the contents of the Configuration Register is a single byte read operation, as shown in Figure 11, the register address previously having been set by a singlebyte write operation to the Address Pointer Register. Reading data from the temperature value, TOTI or THYST Register, is a two-byte operation, as shown in Figure 12. It is also possible to read the most significant bit of a 9-bit/10-bit register in this manner.
1 9
1 SCL
9
SDA START BY MASTER
1
0
0
1
A2
A1
A0
R/W ACK. BY AD7416
P7
P6
P5
P4
P3
P2
P1
P0 ACK. BY AD7416
FRAME 1 SERIAL BUS ADDRESS BYTE 1 SCL (CONTINUED) 9 1
FRAME 2 ADDRESS POINTER REGISTER BYTE 9
SDA (CONTINUED)
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0 ACK. BY AD7416 STOP BY MASTER
ACK. BY STOP BY AD7416 MASTER FRAME 3 MOST SIGNIFICANT DATA BYTE FRAME 4 LEAST SIGNIFICANT DATA BYTE
Figure 10. Writing to the Address Pointer Register Followed by Two Bytes of Data to the TOTI or THYST Register
1 SCL 9 1 9
SDA START BY MASTER
1
0
0
1
A2
A1
A0
R/W ACK. BY AD7416
D7
D6
D5
D4
D3
D2
D1
D0 NO ACK. BY MASTER STOP BY MASTER
FRAME 1 SERIAL BUS ADDRESS BYTE
FRAME 2 SINGLE DATA BYTE FROM AD7416
Figure 11. Reading a Single Byte of Data from the Configuration Register
1 SCL 9 1 9
SDA START BY MASTER
1
0
0
1
A2
A1
A0
R/W ACK. BY AD7416
D15
D14
D13
D12
D11
D10
D9
D8 ACK. BY MASTER
FRAME 1 SERIAL BUS ADDRESS BYTE 1 SCL (CONTINUED)
FRAME 2 MOST SIGNIFICANT DATA BYTE FROM AD7416 9
SDA (CONTINUED)
D7
D6
D5
D4
D3
D2
D1
D0 NO ACK. BY STOP BY MASTER MASTER
FRAME 3 LEAST SIGNIFICANT DATA BYTE FROM AD7416
Figure 12. Reading Two Bytes of Data from the TOTI or THYST Register
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AD7416/AD7417/AD7418
Please note that when reading back from the ADT7416/ ADT7417/ADT7418, no more than three bytes of data must be read back. A STOP command must be inserted at the end of the read communication. If a STOP command is not inserted by the master and the ADT7416/ADT7417/ADT7418 receives more SCL cycles than the maximum needed for three bytes of data, then the I2C interface on the ADT7416/ADT7417/ ADT7418 will pull the SDA line low and prevent it from going high again. To recover the ADT7416/ADT7417/ADT7418 interface the part must be powered off and on again. Reference the application note, AN-686, on the Analog Devices website for more information on I2C interfaces.
OTI OUTPUT
The OTI output requires an external pull-up resistor. This can be connected to a voltage different from VDD (for example, to allow interfacing between 5 V and 3.3 V systems) provided that the maximum voltage rating of the OTI output is not exceeded. The value of the pull-up resistor depends on the application but should be as large as possible to avoid excessive sink currents at the OTI output, which can heat the chip and affect the temperature reading. The maximum value of the pull-up resistor that will meet the output high current specification of the OTI output is 30 k, but higher values may be used if a lower output current is required. For most applications, a value of 10 k will prove suitable.
FAULT QUEUE
The OTI output has two operating modes, which are selected by Bit D1 of the Configuration Register. In the comparator mode, (D1 = 0), the OTI output becomes active when the temperature exceeds TOTI and remains active until the temperature falls below THYST. This mode allows the AD7416/AD7417/ AD7418 to be used as a thermostat, for example, to control the operation of a cooling fan.
TOTI
To avoid false triggering of the AD7416/AD7417/AD7418 in noisy environments, a fault queue counter is provided that can be programmed by Bits D3 and D4 of the Configuration Register (see Table V) to count 1, 2, 4, or 6 fault events before OTI becomes active. In order to trigger OTI, the faults must occur consecutively. For example, if the fault queue is set to 4, then four consecutive temperature measurements greater than TOTI (or less than THYST) must occur. Any reading that breaks the sequence will reset the fault queue counter, so if there are three readings greater than TOTI followed by a reading less than TOTI, the fault queue counter will be reset without triggering OTI.
POWER-ON DEFAULTS
THYST OTI OUTPUT COMPARATOR MODE OTI OUTPUT INTERRUPT MODE READ* READ* READ* READ* READ* READ* READ* *IN INTERRUPT MODE, A READ OPERATION OR SHUTDOWN RESETS THE OTI OUTPUT; OTHERWISE THE OTI OUTPUT REMAINS ACTIVE INDEFINITELY, ONCE TRIGGERED.
The AD7416/AD7417/AD7418 always powers up with the following defaults. Address pointer pointing to Temperature Value Register comparator mode TOTI = 80C THYST = 75C OTI Active LOW Fault Queue = 1 These default settings allow the AD7416/AD7417/AD7418 to be used as a standalone thermostat without any connection to a serial bus.
OPERATING MODES
Figure 13. Operation of OTI Output (Shown Active Low)
The open-drain configuration of OTI allows the OTI outputs of several AD7416/AD7417/AD7418s to be wire-ANDed together when in active low mode. The OTI output is used to indicate that an out-of-limit temperature excursion has occurred. OTI is an open-drain output that can be programmed to be active low by setting Bit D2 of the Configuration Register to 0 or active high by setting Bit D2 of the Configuration Register to 1. In the interrupt mode (D1 = 1), the OTI output becomes active when the temperature exceeds TOTI and remains active even if the temperature falls below THYST, until it is reset by a read operation. Once OTI has become active by the temperature exceeding TOTI, and has then been reset, it will remain inactive even if the temperature remains, or subsequently rises again, above TOTI. It will not become active again until the temperature falls below THYST. It will then remain active until reset by a read operation. Once OTI has become active by the temperature falling below THYST and then reset, it will remain inactive even if the temperature remains, or subsequently falls again, below THYST. OTI is also reset when the AD7416/AD7417/AD7418 is placed in shutdown mode by setting Bit D0 of the Configuration Register to 1.
The AD7416/AD7417/AD7418 has two possible modes of operation depending on the value of D0 in the Configuration Register.
Mode 1
Normal operation of the AD7416/AD7417/AD7418 occurs when D0 = 0. In this active mode, a conversion takes place every 400 s. Once the conversion has taken place, the part partially powers down, consuming typically 350 A of the current until the next conversion occurs. Two situations can arise in this mode on the request of a temperature read. If a read occurs during a conversion, the conversion aborts and a new one starts on the stop/repeat start condition. The temperature value that is read is that of the previous completed conversion. The next conversion will typically occur 400 s after the new conversion has begun. If a read is called between conversions, a conversion is initiated on the stop/repeat start condition. After this conversion, the part returns to performing a conversion every 400 s.
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With a VDD = 3 V, for each 400 s cycle, the AD7416 spends 40 s (or 10% of the time) in conversion mode. It spends 360 s (or 90% of time) in partial power-down mode. Thus, the average power dissipated by the AD7416/AD7417/AD7418 is 3 mW x 0.1 + 1 mW x 0.9 = 1.2 mW
Mode 2
The CONVST pin should not be pulsed when reading from or writing to the port. Figure 17 shows the recommended minimum times for the CONVST pulse when the temperature channel is selected. Figure 18 shows the minimum times an analog input channel is selected.
APPLICATIONS INFORMATION SUPPLY DECOUPLING
For applications where temperature measurements are required at a slower rate, e.g., every second, power consumption of the part can be reduced by writing to the part to go to a full power-down between reads. The current consumption in full power-down is typically 0.2 A and full power-down is initiated when D0 = 1 in the Configuration Register. When a measurement is required, a write operation can be performed to power-up the part. The part then performs a conversion and is returned to power-down. The temperature value can be read in the full power-down because the I2C bus is continuously active. The power dissipation in this mode depends on the rate at which reads take place. Taking the requirements for a temperature measurement every 100 ms as an example, the optimum power dissipation is achieved by placing the part in full power-down, waking it up every 100 ms, letting it operate for 400 s and putting it into full power-down again. In this case, the average power consumption is calculated as follows. The part spends 40 s (or 0.04% of time) converting with 3 mW dissipation and a 99.96 ms (99.96% of time) in full shutdown with 60 nW dissipation. Thus, the average power dissipation is 3 mW x 0.004 + 60 nW x 0.9996 = 1.2 W The fastest throughput rate at which the AD7416/AD7417/ AD7418 can be operated is 2.5 kHz (i.e., a read every 400 s conversion period). Since TOTI and THYST are 2-byte reads, the read time with the I2C operating at 100 kbit/s would be 270 s. If temperature reads are called too often, reads will overlap with conversions, aborting them continuously, which results in invalid readings.
CONVERT START MODE
The AD7416/AD7417/AD7418 should be decoupled with a 0.1 F ceramic capacitor between VDD and GND. This is particularly important if the part is mounted remote from the power supply.
POWER-ON-RESET
To ensure proper power-on-reset, make sure that the supply voltage on the VDD pin is at 0 V. Refer to application note AN-588 for more information. A failed power-on-reset can prevent the default values from being loaded into the AD7416/ AD7417/AD7418 registers. If the correct values are not loaded into the registers, then the device will not start operating. The output from the value registers will be a constant value. To get the device operating again, the registers will have to be loaded with their default values via the I2C bus. Therefore, in the event of an inadequate power-on-reset and for all three devices, the following registers should be loaded with their default values: Configuration Register 1--Default Value = 00h Configuration Register 2--Default Value = 00h THYST Setpoint Register--Default Value = 4B00h TOTI Setpoint Register--Default Value = 5500h
MOUNTING THE AD7416
The AD7417/AD7418 has an extra mode, set by writing to the MSB of the Config2 Register.
CONVST Pin Mode
By setting the CONVST Mode Bit to 1, conversions are initiated only by using the CONVST pin. In this method of operation, CONVST is normally low. The rising edge of CONVST starts the power-up time. This power-up time is 4 s. If the CONVST high time is longer than 4 s, a conversion is initiated on the falling edge of CONVST and the track-and-hold also enters its hold mode at this time. If the CONVST high time is less than 4 s, an internal timer, initiated by the rising edge of CONVST holds off the track-andhold and the initiation of conversion until the timer times out (4 s after the rising edge of CONVST, which corresponds with the power-up time). CONVST input remains low at the end of conversion, thus causing the part to enter its power-down mode. In this method of operation, CONVST is normally low with a high going pulse controlling the power-up and conversion starts.
The AD7416/AD7417/AD7418 can be used for surface or air temperature sensing applications. If the device is cemented to a surface with thermally conductive adhesive, the die temperature will be within about 0.2C of the surface temperature, thanks to the device's low power consumption. Care should be taken to insulate the back and leads of the device from the air, if the ambient air temperature is different from the surface temperature being measured. The ground pin provides the best thermal path to the die, so the temperature of the die will be close to that of the printed circuit ground track. Care should be taken to ensure that this is in good thermal contact with the surface being measured. As with any IC, the AD7416/AD7417/AD7418 and its associated wiring and circuits must be kept free from moisture to prevent leakage and corrosion, particularly in cold conditions where condensation is more likely to occur. Water resistant varnishes and conformal coatings can be used for protection. The small size of the AD7416 package allows it to be mounted inside sealed metal probes that provide a safe environment for the device.
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FAN CONTROLLER THERMOSTAT
Figure 14 shows a simple fan controller that will switch ON a cooling fan when the temperature exceeds 80C and switch it OFF again when the temperature falls below 75C. The AD7416 can be used standalone in this application or with a serial bus interface if different trip temperatures are required. If the AD7416 is used with a bus interface, the sense of OTI can be set to active high, Q1 and R1 can be omitted, and OTI can be connected directly to the gate of Q2 with R2 as the pull-up resistor.
12V
Figure 15 shows the AD7416 used as a thermostat. The heater will be switched ON when the temperature falls below THYST and switched OFF again when the temperature rises above TOTI. For this application and for comparator mode, the OTI output should be programmed active low.
VDD 3V TO 5.5V HEATER
R1 10k
RELAY
D1 1N4001
VDD 3V TO 5.5V
RLA1
AD7416
R1 10k R2 10k Q2 LOGIC LEVEL MOSFET RATED TO SUIT FAN CURRENT
Q1 2N3904 OR SIMILAR
HEATER SUPPLY
AD7416
Q1 2N3904 OR SIMILAR
Figure 15. AD7416 Used as a Thermostat
SYSTEM WITH MULTIPLE AD7416S
Figure 14. AD7416 Used as a Fan Controller
The three LSBs of the AD7416's serial address can be set by the user, allowing eight different addresses from 1001000 to 1001111. Figure 16 shows a system in which eight AD7416s are connected to a single serial bus, with their OTI outputs wire-ANDed together to form a common interrupt line. This arrangement does mean that each device must be read to determine which one has generated the interrupt, and if a unique interrupt is required for each device, the OTI outputs can be connected separately to the I/O chip.
VDD 3V TO 5.5V R1 10k
SUPER I/O CHIP
AD7416
AD7416
AD7416
AD7416
AD7416
AD7416
AD7416
Figure 16. Multiple Connection of AD7416s to a Single Serial Bus
100ns
100ns
CONVST
CONVST
40 s
15 s
Figure 17. CONVST When Temperature Channel Selected
Figure 18. CONVST When VIN Channel(s) Selected
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AD7416/AD7417/AD7418
OUTLINE DIMENSIONS 16-Lead Standard Small Outline Package [SOIC] Narrow Body (R-16)
Dimensions shown in millimeters and (inches)
10.00 (0.3937) 9.80 (0.3858)
16 1 9 8
8-Lead Standard Small Outline Package [SOIC] Narrow Body (R-8)
Dimensions shown in millimeters and (inches)
5.00 (0.1968) 4.80 (0.1890)
8 5 4
4.00 (0.1575) 3.80 (0.1496)
6.20 (0.2441) 5.80 (0.2283)
4.00 (0.1574) 3.80 (0.1497)
1
6.20 (0.2440) 5.80 (0.2284)
1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0039) COPLANARITY 0.10
1.75 (0.0689) 1.35 (0.0531)
0.50 (0.0197) 0.25 (0.0098)
45
0.25 (0.0098) 0.10 (0.0040)
1.27 (0.0500) BSC
1.75 (0.0688) 1.35 (0.0532) 8 0.25 (0.0098) 0 0.17 (0.0067)
0.50 (0.0196) 0.25 (0.0099)
45
8 0.51 (0.0201) SEATING 0.25 (0.0098) 0 1.27 (0.0500) PLANE 0.31 (0.0122) 0.40 (0.0157) 0.17 (0.0067)
COMPLIANT TO JEDEC STANDARDS MS-012AC CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
COPLANARITY SEATING 0.10 PLANE
0.51 (0.0201) 0.31 (0.0122)
1.27 (0.0500) 0.40 (0.0157)
COMPLIANT TO JEDEC STANDARDS MS-012AA CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
16-Lead Thin Shrink Small Outline Package [TSSOP] (RU-16)
Dimensions shown in millimeters
5.10 5.00 4.90
8-Lead Mini Small Outline Package [MSOP] (RM-8)
Dimensions shown in millimeters
3.00 BSC
8
16 9
5
3.00 BSC
6.40 BSC
1 4
4.90 BSC
4.50 4.40 4.30
1 8
PIN 1 0.65 BSC 0.15 0.00
0.20 0.09 0.65 BSC 0.30 0.19 COPLANARITY 0.10 SEATING PLANE 8 0 0.75 0.60 0.45
PIN 1 1.20 MAX
1.10 MAX 8 0 0.80 0.60 0.40
0.15 0.05
0.38 0.22 COPLANARITY 0.10
0.23 0.08 SEATING PLANE
COMPLIANT TO JEDEC STANDARDS MO-187AA
COMPLIANT TO JEDEC STANDARDS MO-153AB
Purchase of licensed I 2C components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the purchaser under the Philips I 2C Patent Rights to use these components in an I 2C system, provided that the system conforms to the I 2C Standard Specification as defined by Philips.
REV. G
-17-
AD7416/AD7417/AD7418 Revision History
Location 8/04--Data Sheet Changed from REV. F to REV. G. Page
Changes to Figure 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Changes to READING DATA FROM THE AD7416/AD7417/AD7418 section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Changes to POWER-ON-RESET section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7/03-Data Sheet Changed from REV. E to REV. F.
Updated FEATURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Updated SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Updated ABSOLUTE MAXIMUM RATINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Updated ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Updated PRODUCT HIGHLIGHTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Updated CIRCUIT INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Updated TEMPERATURE MEASUREMENT section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
10/02-Data Sheet Changed from REV. D to REV. E.
Edits to SPECIFICATIONS headings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Added TEMPERATURE MEASUREMENT section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Edits to SERIAL BUS ADDRESS section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Edits to Figure 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Edits to CONVST Pin Mode section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Edits to POWER-ON-RESET section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Addition of Figures 16 and 17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Updated OUTLINES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
-18-
REV. G
-19-
-20-
C01126-0-8/04(G)

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