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19-3382; Rev 1; 10/04
Digital Temperature Sensors and Thermal Watchdog with Bus Lockup Protection
General Description
The MAX7500/MAX7501/MAX7502 temperature sensors accurately measure temperature and provide an over-temperature alarm/interrupt/shutdown output. These devices convert the temperature measurements to digital form using a high-resolution, sigma-delta, analog-to-digital converter (ADC). Communication is through an I2C-compatible 2-wire serial interface. The MAX7500/MAX7501/MAX7502 integrate a timeout feature that offers protection against I2C bus lockups. The 2-wire serial interface accepts standard write byte, read byte, send byte, and receive byte commands to read the temperature data and configure the behavior of the open-drain over-temperature shutdown output. The MAX7500 features three address select lines, while the MAX7501 and MAX7502 feature two address select lines and a RESET input. The MAX7500/MAX7501/ MAX7502s' 3.0V to 5.5V supply voltage range, low 250A supply current, and a lockup-protected I 2Ccompatible interface make them ideal for a wide range of applications, including personal computers (PCs), electronic test equipment, and office electronics. The MAX7500/MAX7501/MAX7502 are available in 8pin MAX(R) and SO packages and operate over the -55C to +125C temperature range. o o o o
Features
Timeout Prevents Bus Lockup I2C Bus Interface 3.0V to 5.5V Supply Voltage Range 250A (typ) Operating Supply Current
MAX7500/MAX7501/MAX7502
o 3A (typ) Shutdown Supply Current o 2C (max) from -25C to +100C Temperature Accuracy o MAX, SO Packages Save Space o Separate Open-Drain OS Output Operates as Interrupt or Comparator/Thermostat Input o Register Readback Capability o Improved LM75 Second Source
Ordering Information
PART MAX7500MSA MAX7500MUA MAX7501MSA MAX7501MUA MAX7502MSA MAX7502MUA TEMP RANGE -55C to +125C -55C to +125C -55C to +125C -55C to +125C -55C to +125C -55C to +125C PIN-PACKAGE 8 SO 8 MAX 8 SO 8 MAX 8 SO
Applications
PCs Servers Office Electronics Electronic Test Equipment Industrial Process Control
8 MAX I2C is a trademark of Philips Corp. Purchase of I2C components from Maxim Integrated Products Inc., or one of its sublicensed Associated Companies, conveys a license under Philips I2C Patent Rights to use these components in an I2C system, provided that the system conforms to the I2C Standard Specification as defined by Philips.
MAX is a registered trademark of Maxim Integrated Products, Inc.
Pin Configurations
TOP VIEW
SDA SCL OS GND 1 2 3 4 8 +VS A0 A1 A2 SDA SCL OS GND 1 2 3 4 8 +VS A0 A1 RESET
MAX7500
7 6 5
MAX7501 MAX7502 MAX, SO
7 6 5
MAX, SO
________________________________________________________________ Maxim Integrated Products
1
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Digital Temperature Sensors and Thermal Watchdog with Bus Lockup Protection MAX7500/MAX7501/MAX7502
ABSOLUTE MAXIMUM RATINGS
(Note 1) +VS to GND ............................................................. -0.3V to +6V OS, SDA, SCL to GND.......................................... -0.3V to +6.0V All Other Pins to GND ................................ -0.3V to (+VS + 0.3V) Input Current at Any Pin (Note 2) ..................................... +5mA Package Input Current (Note 2) ..................................... +20mA ESD Protection (all pins, Human Body Model, Note 3)... 2000V Continuous Power Dissipation (TA = +70C) 8-Pin MAX (derate 4.5mW/C above +70C) ............ 362mW 8-Pin SO (derate 5.9mW/C above +70C)................. 471mW Operating Temperature Range ....................... -55C to +125C Junction Temperature .................................................... +150C Storage Temperature Range ........................... -65C to +150C Lead Temperature (soldering, 10s) ............................... +300C
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not apply when operating the device beyond its rated operating conditions. Note 2: When the input voltage (VI) at any pin exceeds the power supplies (VI < GND or VI > + VS), the current at that pin should be limited to 5mA. The 20mA maximum package input current rating limits the number of pins that can safely exceed the power supplies with an input current of 5mA to 4. Note 3: Human Body Model, 100pF discharged through a 1.5k resistor.
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
(+VS = +3.0V to +5.5V, TA = -55C to +125C, unless otherwise noted. Typical values are at +VS = +3.3V, TA = +25C.) (Notes 4, 5)
PARAMETER Accuracy Resolution Conversion Time Quiescent Supply Current +VS Supply Voltage Range OS Output Saturation Voltage OS Delay TOS Default Temperature THYST Default Temperature LOGIC (SDA, SCL, A0, A1, A2) Input High Voltage Input Low Voltage Input High Current Input Low Current Input Capacitance Output High Current Output Low Voltage VIH VIL IIH IIL VIN = 5V VIN = 0V All digital inputs VIN = 5V IOL = 3mA 0.005 0.005 5 1 0.4 +VS x 0.7 +VS x 0.3 1.0 1.0 V V A A pF A V IOUT = 4.0mA (Note 7) (Note 8) (Note 9) (Note 9) 1 80 75 (Note 6) I C inactive Shutdown mode, +VS = 3V Shutdown mode, +VS = 5V 3.0
2
SYMBOL
CONDITIONS -25C TA +100C -55C TA +125C
MIN
TYP
MAX 2.0 3.0
UNITS C Bits ms
9 100 0.25 3 5 5.5 0.8 6 0.5
mA A V V Conversions C C
2
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Digital Temperature Sensors and Thermal Watchdog with Bus Lockup Protection
ELECTRICAL CHARACTERISTICS (continued)
(+VS = +3.0V to +5.5V, TA = -55C to +125C, unless otherwise noted. Typical values are at +VS = +5V, TA = +25C.) (Notes 4, 5)
PARAMETER SYMBOL I2C-COMPATIBLE TIMING (Note 10) Serial Clock Frequency Minimum RESET Pulse Width Bus Free Time Between STOP and START Conditions START Condition Hold Time STOP Condition Setup Time Clock Low Period Clock High Period START Condition Setup Time Data Setup Time Data Hold Time Maximum Receive SCL/SDA Rise Time Minimum Receive SCL/SDA Rise Time Maximum Receive SCL/SDA Fall Time Minimum Receive SCL/SDA Fall Time Transmit SDA Fall Time Pulse Width of Suppressed Spike SDA Time Low for Reset of Serial Interface fSCL CONDITIONS Bus timeout inactive MIN DC 1 tBUF tHD:STA tSU:STO tLOW tHIGH tSU:STA tSU:DAT tHD:DAT tR 90% of SCL to 90% of SDA 10% of SDA to 10% of SCL 10% of SCL to 10% of SDA (Note 11) 90% of SCL to 10% of SDA 1.3 0.6 100 1.3 0.6 100 100 0 300 20 + 0.1 x CB 300 20 + 0.1 x CB 20 + 0.1 x CB 0 150 250 50 300 0.9 TYP MAX 400 UNITS kHz s s s ns s s ns ns s ns
MAX7500/MAX7501/MAX7502
tR
(Note 12)
ns
tF
ns
tF
(Note 12)
ns
tF tSP tTIMEOUT
(Note 12) (Note 13) (Note 14)
ns ns ms
Note 4:
Note 5: Note 6: Note 7: Note 8: Note 9: Note 10: Note 11: Note 12: Note 13: Note 14:
All parts operate properly over the +VS = 3V to 5V supply voltage range. The devices are tested and specified for rated accuracy at their nominal supply voltage. Accuracy typically degrades 1C per volt of change in +VS as it varies from the nominal value. All parameters are measured at +25C. Values over the temperature range are guaranteed by design. This specification indicates how often temperature data is updated. The devices can be read at any time without regard to conversion state, while yielding the last conversion result. For best accuracy, minimize output loading. Higher sink currents can affect sensor accuracy due to internal heating. OS delay is user programmable up to six "over-limit" conversions before OS is set to minimize false tripping in noisy environments. Default values set at power-up. All timing specifications are guaranteed by design. A master device must provide a hold time of at least 300ns for the SDA signal to bridge the undefined region of SCL's falling edge. CB = total capacitance of one bus line in pF. Tested with CB = 400pF. Input filters on SDA, SCL, and A_ suppress noise spikes less than 50ns. Holding the SDA line low for a time greater than tTIMEOUT causes the devices to reset SDA to the IDLE state of the serial bus communication (SDA set high).
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Digital Temperature Sensors and Thermal Watchdog with Bus Lockup Protection MAX7500/MAX7501/MAX7502
Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
QUIESCENT SUPPLY CURRENT vs. TEMPERATURE
MAX7500 toc01
SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE
MAX7500 toc02
ACCURACY vs. TEMPERATURE
4 TYPICAL PARTS 1.5 1.0 ACCURACY (C) 0.5 0 -0.5 -1.0
MAX7500 toc03
300 QUIESCENT SUPPLY CURRENT (A) 290 280 270 260 +VS = +3V 250 240 230 -55 -25 5 35 65 95 +VS = +5V
6 SHUTDOWN SUPPLY CURRENT (A) 5 4 3 +VS = +3V 2 1 0 +VS = +5V
2.0
-1.5 -2.0 -55 -25 5 35 65 95 125 -55 -25 5 35 65 95 125 TEMPERATURE (C) TEMPERATURE (C)
125
TEMPERATURE (C)
Pin Description
PIN MAX7500 1 2 3 4 5 -- 6 7 8 MAX7501 MAX7502 1 2 3 4 -- 5 6 7 8 NAME SDA SCL OS GND A2 RESET A1 A0 +VS FUNCTION Serial Data Input/Output Line. Open drain. Connect SDA to a pullup resistor. Serial Data Clock Input. Open drain. Connect SCL to a pullup resistor. Over-Temperature Shutdown Output. Open drain. Connect OS to a pullup resistor. Ground 2-Wire Interface Address Input. Connect A2 to GND or +VS to set the desired I2C bus address. Do not leave floating. (See Table 1.) Active-Low Reset Input. Pull RESET low for longer than the minimum reset pulse width to reset the I2C bus and all internal registers to their POR values. 2-Wire Interface Address Input. Connect A1 to GND or +VS to set the desired I2C bus address. Do not leave floating. (See Table 1.) 2-Wire Interface Address Input. Connect A0 to GND or +VS to set the desired I2C bus address. Do not leave floating. (See Table 1.) Positive Supply Voltage Input. Bypass to GND with a 0.1F bypass capacitor.
Detailed Description
The MAX7500/MAX7501/MAX7502 temperature sensors measure temperature, convert the data into digital form using a sigma-delta ADC, and communicate the conversion results through an I2C-compatible 2-wire serial interface. These devices accept standard I 2C commands to read the data, set the over-temperature
alarm (OS) trip thresholds, and configure other characteristics. The MAX7500 features three address select lines (A0, A1, A2) while the MAX7501 and MAX7502 feature two address select lines (A0, A1) and a RESET input. The MAX7500/MAX7501/MAX7502 operate from +3.0V to +5.5V supply voltages of and consume 250A of supply current.
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Digital Temperature Sensors and Thermal Watchdog with Bus Lockup Protection MAX7500/MAX7501/MAX7502
Table 1. I2C Slave Addresses
DEVICE MAX7500 MAX7501 MAX7502 BIT 7 1 1 1 BIT 6 0 0 0 BIT 5 0 0 0 BIT 4 1 1 1 BIT 3 A2 1 0 BIT 2 A1 A1 A1 BIT 1 A0 A0 A0 BIT 0 RD/W RD/W RD/W
SDA
tSU:DAT tLOW SCL tHD:DAT
tBUF tSU:STA tHD:STA tSU:STO
tHIGH tHD:STA tR START CONDITION (S) PARAMETERS ARE MEASURED FROM 10% TO 90%. tF REPEATED START CONDITION (SR) ACKNOWLEDGE (A) STOP CONDITION (P) START CONDITION (S)
Figure 1. Serial Bus Timing
I2C-Compatible Bus Interface
From a software perspective, the MAX7500/MAX7501/ MAX7502 appear as a set of byte-wide registers that contain temperature data, alarm threshold values, and control bits. A standard I2C-compatible 2-wire serial interface reads temperature data and writes control bits and alarm threshold data. Each device responds to its own I2C slave address, which is selected using A0, A1, and A2. See Table 1. The MAX7500/MAX7501/MAX7502 employ four standard I2C protocols: write byte, read byte, send byte, and receive byte (Figures 1, 2, and 3). The shorter receive byte protocol allows quicker transfers, provided that the correct data register was previously selected
by a read-byte instruction. Use caution when using the shorter protocols in multimaster systems, as a second master could overwrite the command byte without informing the first master. The MAX7500 has eight different slave addresses available; therefore, a maximum of eight MAX7500 devices can share the same bus. The MAX7501/MAX7502 each have four different slave addresses available.
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5
MAX7500/MAX7501/MAX7502
Figure 2. I2C-Compatible Timing Diagram (Write)
Digital Temperature Sensors and Thermal Watchdog with Bus Lockup Protection
6
ADDRESS BYTE ADDRESS BYTE DATA BYTE (a) TYPICAL POINTER SET FOLLOWED BY IMMEDIATE READ FROM CONFIGURATION REGISTER ACK BY MAX7500/ MAX7501/ MAX7502 POINTER BYTE REPEAT START BY MASTER ACK BY MAX7500/ MAX7501/ MAX7502 ACK BY MAX7500/ MAX7501/ MAX7502 NO ACK BY MASTER STOP COND BY MASTER ADDRESS BYTE ACK BY MAX7500/ MAX7501/ MAX7502 POINTER BYTE ACK BY CONFIGURATION MAX7500/ BYTE MAX7501/ MAX7502 (b) CONFIGURATION REGISTER WRITE STOP COND BY ACK BY MASTER MAX7500/ MAX7501/ MAX7502 STOP COND BY MASTER POINTER BYTE ACK BY MAX7500/ MAX7501/ MAX7502 MOST-SIGNIFICANT DATA BYTE ACK BY MAX7500/ MAX7501/ MAX7502 LEAST-SIGNIFICANT DATA BYTE ACK BY MAX7500/ MAX7501/ MAX7502 ADDRESS BYTE ACK BY MAX7500/ MAX7501/ MAX7502 (c) THIGH AND TLOW WRITE
START BY MASTER
START BY MASTER
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START BY MASTER
STOP COND BY MASTER ADDRESS BYTE ACK BY MAX7500/ MAX7501/ MAX7502 MOST-SIGNIFICANT DATA BYTE LEAST-SIGNIFICANT DATA BYTE ACK BY MASTER NO ACK BY MASTER (a) TYPICAL 2-BYTE READ FROM PRESET POINTER LOCATION SUCH AS TEMP, THIGH, TLOW.
Figure 3. I2C-Compatible Timing Diagram (Read)
ADDRESS BYTE ACK BY MASTER POINTER BYTE ACK BY MAX7500/ MAX7501/ MAX7502 STOP COND BY MASTER ACK BY MASTER LEAST-SIGNIFICANT DATA BYTE NO ACK BY MASTER ADDRESS BYTE ACK BY MAX7500/ MAX7501/ MAX7502 MOST-SIGNIFICANT DATA BYTE (b) TYPICAL POINTER SET FOLLOWED BY IMMEDIATE READ FOR 2-BYTE REGISTER SUCH AS TEMP, THIGH, TLOW. ADDRESS BYTE ACK BY MAX7500/ MAX7501/ MAX7502 DATA BYTE NO ACK BY MASTER STOP COND BY MASTER (c) TYPICAL 1-BYTE READ FROM CONFIGURATION REGISTER WITH PRESET POINTER.
START BY MASTER
START BY MASTER
REPEAT START BY MASTER
Digital Temperature Sensors and Thermal Watchdog with Bus Lockup Protection
MAX7500/MAX7501/MAX7502
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START BY MASTER
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Digital Temperature Sensors and Thermal Watchdog with Bus Lockup Protection MAX7500/MAX7501/MAX7502
Table 2. Register Functions
REGISTER NAME Temperature Configuration THYST TOS ADDRESS (hex) 00 01 02 03 POR STATE (hex) -- 00 4B0 500 POR STATE (BINARY) -- 0000 0000 0100 1011 0 0101 0000 0 POR STATE (C) -- -- 75 80 READ/ WRITE Read only R/W R/W R/W
Table 3. Temperature Register Definition
UPPER BYTE D15 Sign bit 1= Negative 0 = Positive D14 MSB 64C D13 32C D12 16C D11 8C D10 4C D9 2C D8 1C D7 LSB 0.5C D6 x D5 x LOWER BYTE D4 x D3 x D2 x D1 x D0 x
X = Don't care.
Register Descriptions
The MAX7500/MAX7501/MAX7502 have an internal pnjunction-based temperature sensor whose analog output is converted to digital form using a 9-bit sigma-delta ADC. The measured temperature and temperature configurations are controlled by the temperature, configuration, T HYST , and T OS registers. See Table 2. Temperature Register Read the measured temperature through the temperature register. The temperature data format is 9 bits, two's complement, and the register is read out in 2 bytes: an upper byte and a lower byte. Bit D15 is the sign bit. When bit D15 is 1, the temperature reading is negative. When bit D15 is zero, the temperature reading is positive. Bits D14-D7 contain the temperature data, with the LSB representing 0.5C and the MSB representing 64C (see Table 3). The MSB is transmit-
ted first. The last 7 bits of the lower byte, bits D6-D0, are don't cares. When reading the temperature register, bits D6-D0 must be ignored. When the measured temperature is greater than +127.5C, the value stored in the temperature register is clipped to 7F8h. When the measured temperature is below -64C, the value in the temperature register is clipped to BF8h. During the time of reading the temperature register, any changes in temperature are ignored until the read is completed. The temperature register is updated upon completion of the next conversion. Table 3 lists the temperature register definition. Configuration Register The 8-bit configuration register sets the fault queue, OS polarity, shutdown control, and whether the OS output functions in comparator or interrupt mode. When writing to the configuration register, set bits D7, D6, and D5 to zero. See Table 5. Bits D4 and D3, the fault queue bits, determine the number of faults necessary to trigger an OS condition. See Table 6. The number of faults set in the queue must occur to trip the OS output. The fault queue prevents OS false tripping in noisy environments. Set bit D2, the OS polarity bit, to zero to force the OS output active low. Set bit D2 to 1 to set the OS output polarity to active high. OS is an open-drain output under all conditions and requires a pullup resistor to output a high voltage. See Figure 4. Set bit D1, the comparator/interrupt bit to zero to run the over-temperature shutdown block in comparator mode. In comparator mode, OS is asserted when the
Table 4. Temperature Data Output
TEMPERATURE (C) +125 +25 +0.5 0 -0.5 -25 -55 DIGITAL OUTPUT BINARY 0111 1101 0xxx xxxx 0001 1001 0xxx xxxx 0000 0000 1xxx xxxx 0000 0000 0xxx xxxx 1111 1111 1xxx xxxx 1110 0110 0xxx xxxx 1100 1000 0xxx xxxx hex 7D0x 190x 008x 000x FF8x E70x C90x
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Digital Temperature Sensors and Thermal Watchdog with Bus Lockup Protection MAX7500/MAX7501/MAX7502
Table 5. Configuration Register Definition
D7 0 D6 0 D5 0 D4 Fault queue D3 Fault queue D2 OS polarity D1 Comparator/ interrupt D0 Shutdown
Table 6. Configuration Register Fault Queue Bits
D4 0 0 1 1 D3 0 1 0 1 NO. OF FAULTS 1 (POR state) 2 4 6
TOS TEMPERATURE THYST
temperature rises above the TOS value. OS is deasserted when the temperature drops below the THYST value. See Figure 4. Set bit D1 to 1 to run the over-temperature shutdown block in interrupt mode. OS is asserted in interrupt mode when the temperature rises above the T OS value or falls below the T HYST value. OS is deasserted only after performing a read operation. Set bit D0, the shutdown bit, to zero for normal operation. Set bit D0 to 1 to shut down the MAX7500/ MAX7501/MAX7502 internal blocks, dropping the supply current to 3A. The I2C interface remains active as long as the shutdown bit is set. The TOS, THYST, and configuration registers can still be written to and read from while in shutdown. TOS and THYST Registers In comparator mode, the OS output behaves like a thermostat. The output asserts when the temperature rises above the limit set in the T OS register. The output deasserts when the temperature falls below the limit set in the THYST register. In comparator mode, the OS output can be used to turn on a cooling fan, initiate an emergency shutdown signal, or reduce system clock speed.
OS OUTPUT (COMPARATOR MODE) OS SET ACTIVE LOW
OS OUTPUT (INTERRUPT MODE) OS SET ACTIVE LOW
READ OPERATION
READ OPERATION
READ OPERATION
Figure 4. OS Timing Diagram
In interrupt mode, exceeding TOS also asserts OS. OS remains asserted until a read operation is performed on any of the registers. Once OS has asserted due to crossing above TOS and is then reset, it is asserted again only when the temperature drops below THYST. The output remains asserted until it is reset by a read. Putting the MAX7500/MAX7501/MAX7502 into shutdown mode also resets OS. The T OS and T HYST registers are accessed with 2 bytes, with bits D15-D7 containing the data. Bits D6-D0 are don't cares when writing to these two registers and read-back zeros when reading from these registers. The LSB represents 0.5C while the MSB represents 64C. See Table 7.
Table 7. TOS and THYST Register Definitions
COMMAND UPPER BYTE D15 Sign bit 1 = negative 0 = positive Sign bit 1 = negative 0 = positive D14 MSB 64C D13 32C D12 16C D11 8C D10 4C D9 2C D8 1C D7 LSB 0.5C D6 x LOWER BYTE D5 x D4 x D3 x D2 x D1 x D0 x
Write
Read
MSB 64C
32C
16C
8C
4C
2C
1C
LSB 0.5C
0
0
0
0
0
0
0
X = Don't care. _______________________________________________________________________________________ 9
Digital Temperature Sensors and Thermal Watchdog with Bus Lockup Protection MAX7500/MAX7501/MAX7502
Shutdown
Set bit D0 in the configuration register to 1 to place the MAX7500/MAX7501/MAX7502 in shutdown mode and reduce supply current to 3A.
+VS
Power-Up and Power-Down
The MAX7500/MAX7501/MAX7502 power up to a known state, as indicated in Table 2. Some of these settings are summarized below: * Comparator mode * TOS = +80C * THYST = +75C * OS active low * Pointer = 00
A0 A1 A2/RESET SDA SCL DATA SMBus INTERFACE BLOCK
MAX7500 MAX7501 MAX7502
OS ADDRESS
Internal Registers
The MAX7500/MAX7501/MAX7502s' pointer register selects between four data registers. See Figure 5. At power-up, the pointer is set to read the temperature register at address 00. The pointer register latches the last location to which it was set. All registers are read and write, except the temperature register, which is read only. Write to the configuration register by writing an address byte, a data pointer byte, and a data byte. If 2 data bytes are written, the second data byte overrides the first. If more than 2 data bytes are written, only the first 2 bytes are recognized while the remaining bytes are ignored. The T OS and T HYST registers require 1 address byte and 1 pointer byte and 2 data bytes. If only 1 data byte is written, it is saved in bits D15-D8 of the respective register. If more than 2 data bytes are written, only the first 2 bytes are recognized while the remaining bytes are ignored. Read from the MAX7500/MAX7501/MAX7502 in one of two ways. If the location latched in the pointer register is set from the previous read, the new read consists of an address byte, followed by retrieving the corresponding number of data bytes. If the pointer register needs to be set to a new address, perform a read operation by writing an address byte, pointer byte, repeat start, and another address byte. An inadvertent 8-bit read from a 16-bit register, with the D7 bit low, can cause the MAX7500/MAX7501/ MAX7502 to stop in a state where the SDA line is held low. Ordinarily, this would prevent any further bus communication until the master sends nine additional clock cycles or SDA goes high. At that time, a stop condition
POINTER REGISTER (SELECTS REGISTER FOR COMMUNICATION) REGISTER SELECT TEMPERATURE (READ ONLY) POINTER = 0000 0000 TOS SET POINT (READ/WRITE) POINTER = 0000 0011 GND CONFIGURATION (READ/WRITE) POINTER = 0000 0001 THYST SET POINT (READ/WRITE) POINTER = 0000 0010
Figure 5. Block Diagram
resets the device. With the MAX7500/MAX7501/ MAX7502, if the additional clock cycles are not generated by the master, the bus resets and unlocks after the bus timeout period has elapsed. The MAX7501/MAX7502 can be reset by pulsing RESET low.
Bus Timeout
Communication errors sometimes occur due to noise pickup on the bus. In the worst case, such errors can cause the slave device to hold the data line low, thereby preventing other devices from communicating over the bus. The MAX7500/MAX7501/MAX7502s' internal bus timeout circuit resets the bus and releases the data line if the line is low for more than 250ms. When the bus timeout is active, the minimum serial clock frequency is limited to 6Hz.
RESET
The RESET input on the MAX7501/MAX7502 provides a way to reset the I2C bus and all the internal registers to their initial POR values. To reset, apply a low pulse with a duration of at least 1s to the RESET input.
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Digital Temperature Sensors and Thermal Watchdog with Bus Lockup Protection
Applications Information
Digital Noise
The MAX7500/MAX7501/MAX7502 feature an integrated lowpass filter on both the SCL and the SDA digital lines to mitigate the effects of bus noise. Although this filtering makes communication robust in noisy environments, good layout practices are always recommended. Minimize noise coupling by keeping digital traces away from switching power supplies. Ensure that digital lines containing high-speed data communications cross at right angles to the SDA and SCL lines. Excessive noise coupling into the SDA and SCL lines on the MAX7500/MAX7501/MAX7502--specifically noise with amplitude greater than 400mV P-P (the MAX7500/MAX7501/MAX7502s' typical hysteresis), overshoot greater than 300mV above +VS , and undershoot more than 300mV below GND--may prevent successful serial communication. Serial bus no-acknowledge is the most common symptom, causing unnecessary traffic on the bus. Care must be taken to ensure proper termination within a system with long PC board traces or multiple parts on the bus. Resistance can be added in series with the SDA and SCL lines to further help filter noise and ringing. If it proves to be necessary, a 5k resistor should be placed in series with the SCL line, placed as close as possible to SCL. This 5k resistor, with the 5pF to 10pF stray capacitance of the MAX7500/MAX7501/ MAX7502 provide a 6MHz to 12MHz lowpass filter, which is sufficient filtering in most cases.
MAX7500/MAX7501/MAX7502
Chip Information
TRANSISTOR COUNT: 9611 PROCESS: CMOS
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Digital Temperature Sensors and Thermal Watchdog with Bus Lockup Protection MAX7500/MAX7501/MAX7502
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
8
4X S
8
INCHES DIM A A1 A2 b c D e E H MIN 0.002 0.030 MAX 0.043 0.006 0.037
MILLIMETERS MAX MIN 0.05 0.75 1.10 0.15 0.95
0.50-0.1
E
H
0.6-0.1
1
0.6-0.1
1
D
L
S
BOTTOM VIEW
0.014 0.010 0.007 0.005 0.120 0.116 0.0256 BSC 0.120 0.116 0.198 0.188 0.026 0.016 6 0 0.0207 BSC
0.25 0.36 0.13 0.18 2.95 3.05 0.65 BSC 2.95 3.05 4.78 5.03 0.41 0.66 0 6 0.5250 BSC
TOP VIEW
A2
A1
A
c e b L
SIDE VIEW
FRONT VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, 8L uMAX/uSOP
APPROVAL DOCUMENT CONTROL NO. REV.
21-0036
J
1 1
12
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8LUMAXD.EPS
Digital Temperature Sensors and Thermal Watchdog with Bus Lockup Protection
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
MAX7500/MAX7501/MAX7502
INCHES DIM A A1 B C e E H L MAX MIN 0.069 0.053 0.010 0.004 0.014 0.019 0.007 0.010 0.050 BSC 0.150 0.157 0.228 0.244 0.016 0.050
MILLIMETERS MAX MIN 1.35 1.75 0.10 0.25 0.35 0.49 0.19 0.25 1.27 BSC 3.80 4.00 5.80 6.20 0.40 1.27
N
E
H
VARIATIONS:
1
INCHES
MILLIMETERS MIN 4.80 8.55 9.80 MAX 5.00 8.75 10.00 N MS012 8 AA 14 AB 16 AC
TOP VIEW
DIM D D D
MIN 0.189 0.337 0.386
MAX 0.197 0.344 0.394
D A e B A1 L C
0 -8
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, .150" SOIC
APPROVAL DOCUMENT CONTROL NO. REV.
21-0041
B
1 1
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13 (c) 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
SOICN .EPS

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