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19-2226; Rev 0; 10/01
Temperature Sensor and System Monitor in a 10-Pin MAX
General Description
The MAX6683 system supervisor monitors multiple power-supply voltages, including its own, and also features an on-board temperature sensor. The MAX6683 converts voltages to an 8-bit code and temperatures to an 11-bit (10-bit-plus-sign) code using an analog-todigital converter (ADC). A multiplexer automatically sequences through the voltage and temperature measurements. The digitized signals are then stored in registers and compared to the over/underthreshold limits programmed over the SMBusTM/I 2CTM-compatible 2wire serial interface. When a temperature measurement exceeds the programmed threshold, or when an input voltage falls outside the programmed voltage limits, the MAX6683 generates a latched interrupt output ALERT. Three interrupt modes are available for temperature excursions. These are default mode, one-time interrupt mode, and comparator mode. The ALERT output is cleared, except for temperature interrupts generated in comparator mode, by reading the Interrupt Status register (Table 5). The ALERT output can also be masked by writing to the appropriate bits in the Interrupt Mask register (Table 6) or by setting bit 1 of the Configuration register (Table 4) to zero. The MAX6683 SMBus/I2Ccompatible interface also responds to the SMB alert response address. o Monitors Local Temperature o Monitors Three External Voltages (1.8V, 2.5V, 5V Nominal) o Monitors VCC (3.3V Nominal) o User-Programmable Voltage and Temperature Thresholds o Alert Function with Ability to Respond to SMB Alert Response Address o +2.7V to +5.5V Supply Range o -40C to +125C Temperature Range o 60Hz or 50Hz Line-Frequency Rejection o Tiny 10-Pin MAX Package o MAX6683EVKIT Available
Features
MAX6683
Ordering Information
PART MAX6683AUB TEMP. RANGE -40C to +125C PIN-PACKAGE 10 MAX
Applications
Workstations Servers Networking Telecommunications
Typical Application Circuit
1.8V VCC = +3.3V CPU 0.1F
Pin Configuration
TOP VIEW
1.8VIN 1 2.5VIN 2 3 4 5 10 VCC 9 SCL SDA ADD ALERT
10k TO 1.8V TO 2.5V TO 5V 1.8VIN 2.5VIN 5VIN N.C. GND VCC SCL SDA ADD ALERT I2C/SMBus CONTROLLER
5VIN N.C. GND
MAX6683
8 7 6
SMBus is a trademark of Intel Corp. I2C is a trademark of Philips Corp. ________________________________________________________________ Maxim Integrated Products 1
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Temperature Sensor and System Monitor in a 10-Pin MAX MAX6683
ABSOLUTE MAXIMUM RATINGS
All Voltages Referenced to GND All Pins...................................................................-0.3V to +6.0V SDA, ALERT Current ...........................................-1mA to +50mA Continuous Power Dissipation (TA = +70C) 10-Pin MAX (derate 5.6mW/C above +70C) ...........444mW Junction Temperature ......................................................+150C Operating Temperature Range .........................-40C to +125C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(TA = -40C to +125C, unless otherwise noted. Typical values are at VCC = +3.3V, TA = +25C.)
PARAMETER POWER SUPPLY Supply Voltage Supply Current Power-On Reset (POR) Voltage TEMPERATURE TA = +25C, VCC = +3.3V Accuracy Resolution Supply Sensitivity ADC CHARACTERISTICS Total Unadjusted Error Differential Nonlinearity Supply Sensitivity Input Resistance Total Monitoring Cycle Time SCL, SDA, ADD Logic Input Low Voltage Logic Input High Voltage Input Leakage Current Output Low Voltage ALERT Output Low Voltage VOLA ISINK = 1.2mA, VCC > 2.7V ISINK = 3.2mA, VCC > 4.5V 0.3 0.4 V VIL VIH ILEAK VOL VCC 3.6V VCC > 3.6V VIN = 0 or 5V ISINK = 3mA 2.0 2.6 1 400 0.8 V V A mV TUE DNL PSS RIN tc 1.8VIN, 2.5VIN, 5VIN (Note 1) 100 VIN > 10LSBs VIN > 10LSBs 1 150 200 200 300 1.5 1 % LSB LSB/V k ms PSS -20C TA +85C, VCC = +3.3V -40C TA +125C, VCC = +3.3V Read word mode 0.125 0.7 1.5 2 3 5 C C/V C VCC ICC ISD Operating Shutdown mode, interface inactive VCC, rising or falling edge 2 2.7 200 5.5 500 10 V A V SYMBOL CONDITIONS MIN TYP MAX UNITS
2
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Temperature Sensor and System Monitor in a 10-Pin MAX
ELECTRICAL CHARACTERISTICS (continued)
(TA = -40C to +125C, unless otherwise noted. Typical values are at VCC = +3.3V, TA = +25C.)
PARAMETER TIMING (Figures 3 and 4) Serial Clock Frequency Bus Free Time Between Stop and Start Start Condition Hold Time Stop Condition Hold Time Clock Low Time Clock High Time Data Setup Time Data Hold Time Receive SCL/SDA Minimum Rise Time Receive SCL/SDA Maximum Rise Time Receive SCL/SDA Minimum Fall Time Receive SCL/SDA Maximum Fall Time Transmit SDA Fall Time Pulse Width of Spike Suppressed fSCL TBUF tHD:STA tSU:STO TLOW THIGH tSU:DAT tHD:DAT tR tR tF tF tF tSP (Note 2) (Note 3) (Note 3) (Note 3) (Note 3) Cb = 400pF, ISINK = 3mA (Note 4) 20 + 0.1Cb 50 0 1.3 0.6 0.6 1.3 0.6 100 0 20 + 0.1Cb 300 20 + 0.1Cb 300 300 0.9 400 kHz s s s s s ns s ns ns ns ns ns ns SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX6683
Note 1: Total monitoring time includes temperature conversion and four analog input voltage conversions. Note 2: A master device must provide at least a 300ns hold time for the SDA signal, referred to VIL of the SCL signal, to bridge the undefined region of SCL's falling edge. Note 3: Cb = total capacitance of one bus line in pF. Rise and fall times are measured between 0.3 VCC to 0.7 VCC. Note 4: Input filters on SDA, SCL, and ADD suppress noise spikes <50ns.
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Temperature Sensor and System Monitor in a 10-Pin MAX MAX6683
Typical Operating Characteristics
(VCC = +3.3V, ADD = GND, TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
INTERFACE INACTIVE A B C D E A: TA = +125C B: TA = +85C C: TA = +25C D: TA = 0C E: TA = -40C 2.5 3.0 3.5 4.0 4.5 5.0 5.5
MAX6683 toc01
SUPPLY CURRENT vs. SCL CLOCK FREQUENCY
MAX6683 toc02
TEMPERATURE ERROR vs. SUPPLY VOLTAGE
3 TEMPERATURE ERROR (C) 2 1 TA = 0C 0 -1 -2 -3 -4 TA = -40C 2.5 3.0 3.5 4.0 4.5 5.0 5.5 TA = +85C
MAX6683 toc03
350 300 SUPPLY CURRENT (A) 250 200 150 100 50 0
450 425 SUPPLY CURRENT (A) 400 375 350 325 300 275 250 1
VCC = +5V SCL = 3Vp-p
4
10
100
1000
SUPPLY VOLTAGE (V)
CLOCK FREQUENCY (kHz)
SUPPLY VOLTAGE (V)
TEMPERATURE ERROR vs. SUPPLY NOISE FREQUENCY
MAX6683 toc04
TEMPERATURE ERROR vs. TEMPERATURE
4 TEMPERATURE ERROR (C) 3 2 1 0 -1 -2 -3 -4
MAX6683 toc05
6 5 TEMPERATURE ERROR (C) 4 3 2 1 0 1
VCC = +5V BYPASS CAP REMOVED 200mVp-p
5
-5 10 100 1k 10k -50 -25 0 25 50 75 100 125 SUPPLY NOISE FREQUENCY (Hz) TEMPERATURE (C)
4
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Temperature Sensor and System Monitor in a 10-Pin MAX
Pin Description
PIN 1 2 3 4 5 6 NAME 1.8VIN 2.5VIN 5VIN N.C. GND ALERT Analog Input. Monitors 1.8V nominal supply. Analog Input. Monitors 2.5V nominal supply. Analog Input. Monitors 5V nominal supply. No Connect. Not internally connected. Connect to GND to improve thermal conductivity. Ground SMBus Alert (Interrupt) Output, Open Drain. Alerts the master that a temperature or voltage limit has been violated. SMBus/I2C-Compatible Address Select Input. ADD is sampled at the beginning of each SMBus/I2C transaction, and the 2LSBs of the Slave Address register are detemined by ADD's connection to GND, SDA, SCL, or VCC. SMBus/I2C-Compatible Serial Data Interface SMBus/I2C-Compatible Clock Input Supply Voltage Input, +2.7V to +5.5V. Also serves as a voltage monitor input. Bypass VCC to GND with a 0.1F capacitor. FUNCTION
MAX6683
7 8 9 10
ADD SDA SCL VCC
Detailed Description
The MAX6683 is a voltage and temperature monitor designed to communicate through an SMBus/I2C interface with an external microcontroller (C). A C with no built-in I2C or SMBus capabilities can generate SMBus serial commands by "bit-banging" general-purpose input-output (GPIO) pins. The MAX6683 can monitor external supply voltages of typically 1.8V, 2.5V, 5V, as well as its own supply voltage and temperature. This makes it ideal for supervisor and thermal management applications in telecommunications, desktop and notebook computers, workstations, and networking equipment. Voltage inputs are converted to an 8-bit code and temperature is converted to an 11-bit code. The high-order 8 bits of the temperature conversion can be read using a read byte operation through the I2C interface. The full 11-bit temperature conversion is read using a read word operation and disregarding the lower 5 bits of the low byte. By setting bit 5 of the Configuration Register to 1, the temperature conversion can be reduced to 9 bits with a four-fold reduction in conversion time. In this case, the lower 7 bits of the low byte should be disregarded; 8bit temperature data has a resolution of 1C/LSB, while 11-bit temperature data has a resolution of 0.125C/ LSB. Setting bit 5 of the Configuration Register to 1 reduces the monitoring cycle time by a factor of 4. In this case, a read word operation for temperature data yields a 9-bit code in which the lower 7 bits of the low byte should be disregarded. The LSB of the 9-bit temperature data has a value of 0.5C.
Each input voltage is scaled down by an on-chip resistive voltage-divider so that its output, at the nominal input voltage, is 3/4 of the ADC's full-scale range, or a decimal count of 192 (Table 3). Input voltages other than the nominal values may be used; ensure that they fall within the usable ranges of pins to which they are applied. Attenuate voltages greater than 6V with an external resistive voltage-divider. Writing a 1 to bit 0 of the Configuration Register starts the monitoring function. The device performs a sequential sampling of all the inputs, starting with the internal temperature sensor and continuing with 2.5VIN, 1.8VIN, 5VIN, and VCC. If the master terminates the conversion, the sequential sampling does not stop until the sampling cycle is completed and the results are stored. When it starts again, it always starts with the temperature measurement. An interrupt signal is generated when a temperature measurement goes above the hot limit or when a voltage measurement is either above the high limit or below the low limit. This causes the open-drain output ALERT to go to the active-low state and set each corresponding interrupt status bit (bits 0 through 4) to 1 (Table 5). The interrupt is cleared by reading the Interrupt Status Register except for temperature interrupts generated in comparator mode. Reading the Interrupt Status Register also clears the register itself, except for temperature interrupt bits set in comparator mode.
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Temperature Sensor and System Monitor in a 10-Pin MAX MAX6683
Table 1. Register Map
ADDRESS 20h 21h 22h 23h 27h 2Bh 2Ch 2Dh 2Eh 2Fh 30h 31h 32h 39h 3Ah 40h 41h 43h READ/WRITE R R R R R R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R R/W POWER-ON DEFAULT -- -- -- -- -- 1101 0011 (1.1 x 2.5V) 1010 1101 (0.9 x 2.5V) 1101 0011 (1.1 x 1.8V) 1010 1101 (0.9 x 1.8V) 1101 0011 (1.1 x 5V) 1010 1101 (0.9 x 5V) 1101 0011 (1.1 x 3.3V) 1010 1101 (0.9 x 3.3V) 0101 0000 (+80C) 0100 0001 (+65C) 0000 1000 0000 0000 0000 0000 DESCRIPTION Data register for 2.5 VIN measurement Data register for 1.8VIN measurement Data register for 5VIN measurement Data register for VCC measurement Data register for temperature measurement High limit for 2.5VIN Low limit for 2.5VIN High limit for 1.8VIN Low limit for 1.8VIN High limit for 5VIN Low limit for 5VIN High limit for VCC Low limit for VCC Hot temperature limit Hot temperature hysteresis Configuration Register Interrupt Status Register Interrupt Mask Register Device Address Register. The values of XX are dependent on the status of the ADD pin. Power-On Default ADD Connection 0010 100Y To GND 0010 101Y To VCC 0010 110Y To SDA 0010 111Y To SCL Y (bit 0) is the SMBus read/write bit. When the 7-bit chip address is read back from the Serial Address Register, an 8-bit word is presented with a zero in bit 0 (Y). Temperature Configuration Register
48h
R/W
0010 1XXY
4Bh
R/W
0000 0000
Unless the fault is removed, the ALERT output only remains cleared until the end of the next conversion cycle where it is again asserted. The ALERT output can also be masked by writing to the appropriate bits in the Interrupt Mask Register (Table 6) or by setting bit 1 of the Configuration Register (Table 4) to zero. The 2-wire serial interface accepts both I2C and standard SMBus Write Byte, Read Byte, Read Word, Send Byte, and Receive Byte commands to program the alarm thresholds and to read voltage and temperature data. Voltage data is scaled so that when the nominal voltage is present at an input (e.g., 1.8V for the 1.8VIN input), the conversion result is equal to 3/4 of the ADC full-scale range or a decimal count of 192 (Table 1).
6
When using the Read Byte command, the temperature data format is 7 bits plus sign with the LSB equal to 1C, in two's complement format. When using the Read Word command, the temperature data format is 10 bits plus sign, with the LSB equal to 0.125C, in two's complement format. See Table 2 for the temperature data format. The MAX6683 has only one address input, ADD. Connect ADD to GND, VCC , SDA, or SCL to select one of four different address codes. Whenever an SMBus/I 2C transaction is initiated, the 2LSBs of the Slave Address Register are determined by connection, setting the chip address to one of four possible values. In addition, an address code can also be directly writ-
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Temperature Sensor and System Monitor in a 10-Pin MAX
Table 2. Temperature Data Format (Two's Complement)
HIGH BYTE TEMPERATURE (C) +125 +25 +1 0 -1 -25 -40 LOW BYTE 0.875 0.125 1110 0000 0010 0000 D0 20 DIGITAL OUTPUT (BINARY) 0111 1101 0001 1001 0000 0001 0000 0000 1111 1111 1110 0111 1101 1000 DIGITAL OUTPUT (HEX) 7D 19 01 00 FF E7 D8
voltage. This is equivalent to 4 and 2 cycles of 60Hz, respectively, and provides protection against noise pickup from the main supply. The internal oscillator frequency can be changed to provide the same protection against 50Hz by setting bit 7 in the Configuration Register to 1 (Table 4). The multiplexer automatically sequences through the inputs, measuring voltages and temperature.
MAX6683
Low-Power Shutdown Mode
Setting bit 0 in the Configuration Register to zero stops the monitoring loop and puts the MAX6683 into lowpower shutdown mode. In this mode, the SMBus/I2C interface remains active, and the supply current drops to 10A or less.
Power-On Reset
The MAX6683 POR supply voltage is typically 2V. Below this supply voltage, all registers are reset, the device is put into shutdown mode, and the SMBus/I2C interface is inactive.
ten to the Serial Address Register. This code overwrites the code set by connection of the ADD pin, until the MAX6683 is taken through a POR cycle.
Alarm Threshold Registers
Two registers, a hot temperature limit (THOT) at 39h and a hot temperature hysteresis (T HYST ) at 3Ah, store alarm threshold data (Table 1). If a measured temperature exceeds the value of THOT, an ALERT is asserted. Alerts are cleared and reasserted depending on the interrupt mode selected in the Temperature Configuration Register (see ALERT Interrupts).
ADC and Multiplexer
The ADC integrates over a 66ms period, an integral multiple of the line period with excellent noise rejection. The internal oscillator is trimmed to produce a 66ms conversion time for temperature and 33ms for each
Table 3. Voltage Data Format
ADC OUTPUT CODE LSB weight 0 1 2 -- 64 (1/4 scale) -- 128 (1/2 scale) -- 192 (3/4 scale) -- 253 254 255 INPUT VOLTAGE AT 1.8VIN 9.375mV (1.8V/192) < 9.375mV 9.375mV to 18.75mV 18.75mV to 28.125mV -- 600mV to 609.4mV -- 1.2V to 1.2094V -- 1.8V to 1.737V -- 2.372V to 2.381V 2.381V to 2.391V = 2.391V INPUT VOLTAGE AT 2.5VIN 13mV (2.5V/192) < 13mV 13mV to 26mV 26mV to 39mV -- 833mV to 846mV -- 1.667V to 1.680V -- 2.5V to 2.513V -- 3.294V to 3.307V 3.572V to 3.586V = 3.586V INPUT VOLTAGE AT 5VIN 26mV (5V/192) < 26mV 26mV to 52mV 52mV to 78mV -- 1.664V to 1.692V -- 3.330V to 3.560V -- 5V to 5.026V -- 6.566V to 6.640V 6.615V to 6.640V = 6.640V VCC = +3.3V 17.2mV (3.3V/192) -- -- -- -- -- -- -- -- 3.3V to 3.317V -- 4.348V to 4.366V 4.366V to 4.383V = 4.383V
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Temperature Sensor and System Monitor in a 10-Pin MAX MAX6683
Table 4. Configuration Register (Address 40h, Power-On Default = 08h)
BIT NAME READ/WRITE DESCRIPTION This bit controls the monitoring loop. Setting the bit to zero stops the monitoring loop and puts the device into shutdown mode. The I2C/SMBus interface is still active during the shutdown mode. Setting the bit to 1 starts the monitoring cycle. All high/low limits should be set before setting this bit to 1. This bit is used to enable or disable the ALERT output. Setting the bit to 1 enables the ALERT output; setting the bit to 0 disables the ALERT output. -- This bit is used to clear the ALERT output when it is set to high. It does not affect the Interrupt Status Register. The monitoring loop does not start until the bit is set to zero. This bit controls the internal clock frequency. Setting the bit to 1 changes the clock frequency to 51.2kHz from 61.4kHz. This can improve the measurement accuracy when the power-line frequency is at 50Hz. This bit reduces the conversion time by a factor of 4 when it is set to 1. -- This bit is used as a reset signal for the register initialization. The 1 of this bit resets all the register values into the power-up default mode, including bit 7 itself.
0
Start/Stop
R/W
1 2 3
ALERT Enable Reserved ALERT Clear
R/W -- R/W
4 5 6 7
Line Frequency Select Short Cycle Reserved Reset
R/W R/W -- R/W
Table 5. Interrupt Status Register (Address 41h, Power-Up Default = 00h)
BIT 0 1 2 3 NAME 2.5VIN-Error 1.8VIN-Error 5VIN-Error VCC-Error READ/WRITE R R R R DESCRIPTION A 1 indicates either a high or low limit has been exceeded at the 2.5VIN input. A 1 indicates either a high or low limit has been exceeded at the 1.8VIN input. A 1 indicates either a high or low limit has been exceeded at the 5VIN input. A 1 indicates either a high or low limit has been exceeded at the VCC input. A 1 indicates either a high or low limit has been exceeded at the internal temperature sensor. The conditions that generate and clear this bit depend on the temperature interrupt mode selected by bits 0 and 1 in the Temperature Configuration Register. --
4
Temp-Error
R
5, 6, 7
Reserved
--
The POR state of the THOT register is 0101 0000 or +80C. The POR state of the THYST register is 0100 0001 or +65C. High and low limits for the voltage inputs are stored in registers 2Bh through 32h. If a measured voltage is less than VLOW or greater than VHIGH, an ALERT is asserted. The POR states of the high and low voltage limits are 1.1 and 0.9 times the nominal voltage for each input.
Interrupt Status Byte Functions
The Interrupt Status Register records temperature or voltage fault conditions whenever a limit is exceeded (Table 5). Bits 0 through 3 correspond to the 2.5V, 1.8V, 5V, and VCC voltage inputs and bit 4 corresponds to the temperature. If a threshold has been crossed, the appropriate bit contains a 1. In the default and one-time interrupt modes, reading the status register clears the register until a new out-of-range condition is detected.
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Temperature Sensor and System Monitor in a 10-Pin MAX MAX6683
Table 6. Interrupt Mask Register (Address 43h, Power-Up Default = 00h)
BIT 0 1 2 3 4 5, 6, 7 NAME 2.5V 1.8V 5V 3.3V Temp. Reserved READ/WRITE R/W R/W R/W R/W R/W -- DESCRIPTION Setting the bit to 1 disables the Interrupt Status Register bit (bit 0) and the ALERT output for the 2.5VIN input. Setting the bit to 1 disables the Interrupt Status Register bit (bit 1) and the ALERT output for the 1.8VIN input. Setting the bit to 1 disables the Interrupt Status Register bit (bit 2) and the ALERT output for the 5VIN input. Setting the bit to 1 disables the Interrupt Status Register bit (bit 3) and the ALERT output for the VCC input. Setting the bit to 1 disables the Interrupt Status Register bit (bit 4) and the ALERT output for temperature. --
Table 7. Temperature Configuration Register (Address 4Bh, Power-Up Default = 00h)
BIT NAME Hot Temperature Interrupt Select Reserved READ/WRITE DESCRIPTION Bit 1, bit 0 = 00: Default mode Bit 1, bit 0 = 01: One-time interrupt mode Bit 1, bit 0 = 10: Comparator mode Bit 1, bit 0 = 11: Default mode --
0, 1
R/W
2-7
--
ALERT Interrupts
An out-of-range voltage or temperature causes the ALERT output signal to be asserted. However, if the assertion is caused by an out-of-range temperature, the ALERT output can operate in one of three different modes: default, one-time interrupt, or comparator mode. In the default and one-time interrupt modes, the ALERT signal and Interrupt Status Register are cleared by reading the Interrupt Status Register (Table 5). In comparator mode, ALERT is only cleared when the fault condition is removed. Reading the Interrupt Status Register clears all but bit 4 of the Status Register if the fault condition is not removed. Reading the Interrupt Status Register with the fault condition removed clears the entire register. Unless the fault is removed, ALERT is reasserted after the next conversion cycle. The ALERT output can also be masked by writing to the appropriate bits in the Interrupt Mask Register (Table 6) or by setting bit 1 of the Configuration Register (Table 4) to zero. The interrupt does not halt conversions. New temperature and voltage data continue to be available over the SMBus interface after ALERT is asserted. The three
temperature ALERT modes are shown in Figure 1 and are selected through the Temperature Configuration Register (Table 7). The ALERT output pin is open drain, so the device can share a common interrupt line. Default Mode An interrupt is initiated when temperature exceeds THOT (address 39h). The interrupt is cleared only by reading the Interrupt Status Register. An interrupt continues to be generated on subsequent measurements until the temperature goes below THYST (address 3Ah). One-Time Interrupt Mode An interrupt is initiated when temperature exceeds THOT (address 39h). The interrupt is cleared only by reading the Interrupt Status Register. The next interrupt is then initiated when temperature falls below the THYST (address 3Ah). Comparator Mode An interrupt is initiated when temperature exceeds THOT (address 39h). The ALERT output remains asserted low until the temperature goes below THOT. Reading the Interrupt Status Register does not clear the ALERT output or interrupt status bit in the register. The inter9
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Temperature Sensor and System Monitor in a 10-Pin MAX MAX6683
TEMPERATURE MONITORING CYCLE INTERRUPT STATUS READ THOT THYST ALERT DEFAULT MODE ALERT ALERT ONE-TIME INTERRUPT MODE COMPARATOR MODE
Figure 1. Alert Response to Temperature Interrupts
Write Byte Format S ADDRESS 7 bits W/R 0 ACK COMMAND 8 bits Command Byte: selects which register you are writing to ACK DATA 8 bits Data Byte: data goes into the register set by the co mma nd byte ( to se t thresholds, configuration masks, and sampling rate) ACK P
Slave Address: equivalent to chip-select line of a 3-wire interface Read Byte Format S ADDRESS 7 bits W/R 0 ACK COMMAND 8 bits
ACK
S
ADDRESS 7 bits
W/R 1
ACK
DATA 8 bits
A
P
Slave Address: equivalent to chip-select line of a 3-wire interface Send Byte Format S ADDRESS 7 bits W/R 0 ACK
Command Byte: selects which register you are reading from
Slave Address: repeated due to change in dataflow direction Receive Byte Format
Data Byte: reads from the register set by the command byte
COMMAND 8 bits
ACK
P
S
ADDRESS 7 bits
W/R 1
ACK
DATA 8 bits
A
P
Data Byte: writes data to the register commanded by the last Read Byte or Write Byte transmission Read Word Format S ADDRESS 7 bits S = Start condition P = Stop condition W/R 0 ACK COMMAND 8 bits ACK S ADDRESS 7 bits W/R ACK 1
Data Byte: reads data from the register commanded by the last Read Byte or Write Byte transmission; also used for SMBus alert Response return address DATA_LOW_byte 8 bits ACK DATA_HIGH_byte 8 bits A P
Shaded = Slave transmission A = Not acknowledged
Figure 2. SMBus Protocols
10
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Temperature Sensor and System Monitor in a 10-Pin MAX MAX6683
A tLOW B tHIGH C D E F G H I J K L M
SMBCLK
SMBDATA
tSU:STA
tHD:STA
tSU:DAT
tHD:DAT
tSU:STO tBUF
A = START CONDITION B = MSB OF ADDRESS CLOCKED INTO SLAVE C = LSB OF ADDRESS CLOCKED INTO SLAVE D = R/W BIT CLOCKED INTO SLAVE E = SLAVE PULLS SMBDATA LINE LOW
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER G = MSB OF DATA CLOCKED INTO SLAVE H = LSB OF DATA CLOCKED INTO SLAVE I = SLAVE PULLS SMBDATA LINE LOW
J = ACKNOWLEDGE CLOCKED INTO MASTER K = ACKNOWLEDGE CLOCK PULSE L = STOP CONDITION, DATA EXECUTED BY SLAVE M = NEW START CONDITION
Figure 3. SMBus Write Timing Diagram
A
tLOW
B
tHIGH
C
D
E
F
G
H
I
J
K
L
M
SMBCLK
SMBDATA
tSU:STA
tHD:STA
tSU:DAT E = SLAVE PULLS SMBDATA LINE LOW F = ACKNOWLEDGE BIT CLOCKED INTO MASTER G = MSB OF DATA CLOCKED INTO MASTER H = LSB OF DATA CLOCKED INTO MASTER I = MASTER PULLS DATA LINE LOW
tSU:STO tBUF J = ACKNOWLEDGE CLOCKED INTO SLAVE K = ACKNOWLEDGE CLOCK PULSE L = STOP CONDITION M = NEW START CONDITION
A = START CONDITION B = MSB OF ADDRESS CLOCKED INTO SLAVE C = LSB OF ADDRESS CLOCKED INTO SLAVE D = R/W BIT CLOCKED INTO SLAVE
Figure 4. SMBus Read Timing Diagram
rupt continues to be generated on subsequent measurements until the temperature falls below THOT.
Slave Address
The device address can be set to one of four different values by pin strapping ADD to GND, SDA, SCL, or VCC, so more than one MAX6683 can reside on the same bus without address conflicts (Table 1). The address pin state is checked at the beginning of each SMBus/I2C transaction and is insensitive to glitches on VCC. Any address code can also be written to the Serial Address Register and overwrites the code set by connecting the ADD pin until the MAX6683 is taken through a POR cycle.
SMBus/I2C-Compatible Digital Interface
From a software prospective, the MAX6683 appears as a set of byte-wide registers that contain voltage and temperature data, alarm threshold values, or control bits. The device employs five standard SMBus protocols: write byte, read byte, read word, send byte, and receive byte (Figures 2, 3, 4).
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Temperature Sensor and System Monitor in a 10-Pin MAX MAX6683
UPPER BYTE D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 LOWER BYTE X X X X X
11-BIT READ FORMAT UPPER BYTE D8 D7 D6 D5 D4 D3 D2 D1 D0 X X LOWER BYTE X X X X X
9-BIT READ FORMAT
X = DON'T CARE
Figure 5. Read Temperature Format
The MAX6683 also responds to the SMBus alert response address (see Alert Response Address).
*
Alert Response Address
The SMBus alert response interrupt pointer provides quick fault identification for simple slave devices that lack the complex, expensive logic needed to be a bus master. Usually the ALERT outputs of several slave devices are wire-ORed to the same interrupt input of the host master. Upon receiving an interrupt signal, the host master can broadcast a receive byte transmission (Figure 2) with the alert response address (0001 100). A read operation is denoted by a 1 in the eighth address bit. Then, any slave device that generated an interrupt attempts to identify itself by putting its own address on the bus. The alert response can activate several different slave devices simultaneously, similar to the I2C general call. If more than one slave attempts to respond, bus arbitration rules apply, and the device with the lower address code wins. The losing device does not generate an acknowledge signal and continues to hold the interrupt line low until serviced. The MAX6683 does not automatically clear its ALERT when it responds to an alert response address. The host master must then clear or mask the ALERT by reading the Interrupt Status Register, writing to the Interrupt Mask Register, or setting bit 1 of the Configuration Register to zero before it can identify other slaves generating an interrupt. * * *
Bit 0 puts the MAX6683 into software standby mode (STOP) or autoconvert (START) mode. The 2-wire interface is still active in the standby mode. All voltage and temperature limits should be set before setting this bit to 1. Bit 1 enables and disables the ALERT output. Setting this bit to 1 enables the ALERT output. Bit 2 is reserved. Bit 3 clears the ALERT output and stops the monitoring loop when set to 1. Clearing the output does not affect the contents of the Interrupt Status Registers. Bit 4 sets the analog-to-digital conversion speed to minimize interference from power-line frequencies. Setting this bit to 1 can improve accuracy when the power-line frequency is 50Hz. When the power-line frequency is 60Hz, bit 4 should be zero. Bit 5 reduces the oversampling ratio in the ADC from 8 to 2. This reduces the monitoring cycle time by a factor of 4 to typically 50ms at the cost of reduced noise rejection. Bit 6 is reserved. Bit 7 resets all register values to their power-up default values. To reset all registers, set bit 7 to 1. This also resets bit 7 to its power-up value of zero.
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Read Temperature
The MAX6683 reads out temperature in an 8-, 9-, or 11-bit two's complement format. To obtain the 8-bit temperature data (7 bits plus sign), execute a Read Byte command to the Temperature Data Register (address 27h). To obtain the 11-bit temperature data (10 bits plus sign), execute a Read Word command to the Temperature Data Register (address 27h). When performing a Read Word operation, the MAX6683 writes the 11 bits of data to the bus in two 8-bit words. The
Command Byte Functions
The 8-bit Command Byte Register (Table 1) is the master index that points to the other data, configuration, limits, and address registers within the MAX6683. The functions of those other registers are described below.
Configuration Byte Functions
The Configuration Register (Table 4) is a read-write register with several functions:
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Temperature Sensor and System Monitor in a 10-Pin MAX
Functional Diagram
VCC
Applications Information
Sensing Circuit Board and Component Temperatures
Temperature sensor ICs like the MAX6683 that sense their own die temperatures must be mounted on or close to the object whose temperature they are intended to measure. Because there is a good thermal path between the 10-pin MAX package's metal leads and the IC die, the MAX6683 can accurately measure the temperature of the circuit board to which it is soldered. If the sensor is intended to measure the temperature of a heat-generating component on the circuit board, it should be mounted as close as possible to that component and should share supply and ground traces (if they are not noisy) with that component where possible. This maximizes the heat transfer from the component to the sensor. The thermal path between the plastic package and the die is not as good as the path through the leads, so the MAX6683, like all temperature sensors in plastic packages, is less sensitive to the temperature of the surrounding air than to the temperature of the leads. Wiring and circuits must be kept insulated and dry to avoid leakage and corrosion, especially if they operate at cold temperatures where condensation can occur.
MAX6683
1.8VIN 2.5VIN 5.0VIN
INPUT VOLTAGE SCALING AND MULTIPLEXER
ADC
DATA AND CONTROL LOGIC
TEMPERATURE SENSOR
VOLTAGE REFERENCE
I2C/SMBusCOMPATIBLE INTERFACE
SDA SCL ALERT ADD
upper byte contains the MSBs, while the lower byte contains the 3LSBs (Figure 5). D9-D3 of the upper byte represent the whole decimal number of the temperature conversion and D10 is sign. D2-D0 of the lower byte represent 1/2, 1/4, 1/8 of a degree, respectively, and the remaining bits are disregarded. Nine-bit temperature data (8 bits plus sign) is obtained by setting bit 5 of the Configuration Register (address 40h) to 1, reducing the conversion time by a factor of four, and executing a Read Word command to the Temperature Data Register (address 27h). The upper byte contains the MSBs, while the lower byte contains the LSB (Figure 5). D7-D1 of the upper byte represent the whole decimal number of the temperature conversion and D0 is sign. D0 of the lower byte represents 1/2 of a degree, and the remaining bits are disregarded.
Chip Information
TRANSISTOR COUNT: 13,446 PROCESS: BiCMOS
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Temperature Sensor and System Monitor in a 10-Pin MAX MAX6683
Package Information
10LUMAX.EPS Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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