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19-1959; Rev 1; 8/01
Temperature Sensor and System Monitor in a 10-Pin MAX
General Description
The MAX6652 system supervisor monitors multiple power-supply voltages, including its own, and also features an on-board temperature sensor. Voltages and temperature are converted to an 8-bit code using an analog-to-digital 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/under threshold limits programmed over the 2-wire serial interface. When a temperature measurement exceeds the programmed threshold, or when an input voltage falls outside the programmed voltage limits, the MAX6652 generates a latched interrupt output ALERT. Three interrupt modes are available for temperature excursions: 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 0. The MAX6652 I 2 C TM -compatible/SMBus interface also responds to the SMB alert response address. The 2-wire serial interface accepts both I C and standard system management bus (SMBus) write byte, read byte, 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 a pin (e.g., 3.3V for the 3.3VIN pin), the conversion result is equal to 3/4 of the ADC full-scale range or a decimal count of 192 (Table 3). The temperature data format is 7 bits plus sign, with each data bit representing 1C, in two's complement format (Table 2). The MAX6652 has only one address pin, ADD. One of four different address codes can be selected by connecting the ADD pin to GND, V CC , SDA, or SCL. 2 Whenever an I C-compatible/SMBus transaction is initiated, the two LSBs 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 written to the serial address register. This code will overwrite the code set by connection of the ADD pin, until the MAX6652 is taken through a power-on reset cycle. The MAX6652 features 60Hz or 50Hz line-frequency rejection for optimal performance. The device operates from +2.7V to +5.5V and is specified for operation from -40C to +125C. It is available in a tiny 10-pin MAX package.
I C is a trademark of Philips Corp.
2 2
Features
o Monitors Four Voltages (2.5V, 3.3V, 12V, VCC) o Monitors Local Temperature o Temperature Measurement Accuracy, 2C (TA = +25C) 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
MAX6652
Applications
Workstations Servers Networking Telecommunications
Ordering Information
PART MAX6652AUB TEMP. RANGE -40C to +125C PIN-PACKAGE 10 MAX
Pin Configuration
TOP VIEW
12VIN 1 2.5VIN 3.3VIN N.C. GND 2 3 4 5 10 VCC 9 SCL SDA ADD ALERT
MAX6652
8 7 6
MAX
Typical Application Circuit and Functional Diagram appear at end of data sheet. 1
________________________________________________________________ Maxim Integrated Products
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Temperature Sensor and System Monitor in a 10-Pin MAX MAX6652
ABSOLUTE MAXIMUM RATINGS
All Voltages Are Referenced to GND VCC ........................................................................-0.3V to +6.0V Voltage on 12VIN ...................................................-0.3V to +16V All Other Pins ........................................................-0.3V to +6.0V Output Current (SDA, ALERT) ............................-1mA to +50mA Junction Temperature .....................................................+150C Operating Temperature Range ........................-40C to +125C Storage Temperature Range ............................-65C to +150C Continuous Power Dissipation (TA = +70C) 10-Pin MAX (derate 5.6mW/C above +70C) ..........444mW 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 = +5V, TA = +25C.)
PARAMETER POWER SUPPLY Supply Voltage Supply Current Power-On Reset Voltage TEMPERATURE TA = +25C Accuracy (Note 5) PSRR Resolution 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 SDA Output Low Voltage Input Leakage Current ALERT Output Low Voltage TIMING Serial Clock Frequency Bus Free Time Between STOP and START fSCL tBUF 0 1.3 400 kHz s VOLA ISINK = 1.2mA, VCC > 2.7V ISINK = 3.2mA, VCC > 4.5V 0.3 0.4 V V VIL VIH VOL ILEAK VCC 3.6V VCC > 3.6V ISINK = 3mA VIN = 0 or 5V 2.0 2.6 400 1 0.8 V V V mV A TUE DNL PSS RIN tc VIN > 10LSB VIN > 10LSB VCC = +2.7V to +5.5V 12VIN, 2.5VIN, 3.3VIN (Note 1) 100 1 150 200 200 300 1 1.5 1 % LSB V k ms VCC = +5V VCC = +2.7V to +5.5V -20C TA +80C -40C TA +125C 0.7 1 2 3 5 1.3 C/V C C VCC ICC ISD Active Shutdown mode, all digital inputs are grounded VCC_ rising or falling edge 2.7 200 <1 2 5.5 500 10 V A 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 = +5V, TA = +25C.)
PARAMETER START Condition Hold Time STOP Condition Hold Time Clock Low Period Clock High Period 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 SYMBOL tHD:STA tSU:STO tLOW tHIGH tSP:DAT tHD:DAT tR tR tF tF tF tSP (Note 2) (Note 3) (Note 3) (Note 3) (Note 3) 400pF, ISINK = 3mA (Note 4) 20 + 0.1CB 50 CONDITIONS MIN 0.6 0.6 1.3 0.6 100 0 20 + 0.1CB 300 20 + 0.1CB 300 300 0.9 TYP MAX UNITS s s s s ns s ns ns ns ns ns ns
MAX6652
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 x VCC to 0.7 x VCC. Note 4: Input filters on SDA, SCL, and ADD suppress noise spikes <50ns. Note 5: Guaranteed but not tested over the entire temperature range.
Typical Operating Characteristics
(VCC = +5V, ADD = GND, ALERT = 10k to VCC, TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX6652 toc01
SUPPLY CURRENT vs. SCL CLOCK FREQUENCY
MAX6652 toc02
TEMPERATURE ERROR vs. SUPPLY VOLTAGE
4 TEMPERATURE ERROR (C) 3 2 1 0 -1 -2 -3 -4 TA = -40C TA = 0C TA = +85C
MAX6652 toc03
300 A 250 SUPPLY CURRENT (A) 200 150 100 50 0 2.5 3.0 3.5 4.0 4.5 5.0 B C D E A: TA = +125C B: TA = +85C C: TA = +25C D: TA = 0C E: TA = -40C
250 VCC = +5V SCL = 0 to +5V SUPPLY CURRENT (A) 225
5
200
175
150 5.5 1 1000 CLOCK FREQUENCY (kHz) SUPPLY VOLTAGE (V)
-5 2.5 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V)
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Temperature Sensor and System Monitor in a 10-Pin MAX MAX6652
Typical Operating Characteristics (continued)
(VCC = +5V, ADD = GND, ALERT = 10k to VCC, TA = +25C, unless otherwise noted.)
TEMPERATURE ERROR vs. SUPPLY NOISE FREQUENCY
1 0 TEMPERATURE ERROR (C) -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 1 1k SUPPLY NOISE FREQUENCY (kHz) 10 100 10k VCC = +5V BYPASS CAP REMOVED 200mVp-p
MAX6652 toc04
TEMPERATURE ERROR vs. TEMPERATURE
0.75 TEMPERATURE ERROR (C) 0.50 0.25 0 -0.25 -0.50 -0.75 -1.00 -50 -25 0 25 75 50 TEMPERATURE (C) 100 125
MAX6652 toc05
2
1.00
Pin Description
PIN 1 2 3 4 5 6 NAME 12VIN 2.5VIN 3.3VIN N.C. GND ALERT Analog Input. Monitors 12V supply. Analog Input. Monitors 2.5V supply. Analog Input. Monitors 3.3V supply. No Connection. Can be connected 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 Address Select Input. ADD is sampled at the beginning of each I C-compatible/SMBus transaction, and the 2 LSBs of the slave address register are detemined by ADD's connection to GND, SDA, SCL, or VCC. I C-Compatible/SMBus Serial Data Interface I C-Compatible/SMBus Serial 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.
2 2 2
FUNCTION
7 8 9 10
ADD SDA SCL VCC
4
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Temperature Sensor and System Monitor in a 10-Pin MAX
Detailed Description
The MAX6652 is a voltage and temperature monitor designed to communicate through an I2C-compatible/ SMBus interface with an external microcontroller (C). A C with no built-in I2C-compatible or SMBus capabilities can generate SMBus serial commands by "bitbanging" general-purpose input-output (GPIO) pins. The MAX6652 can monitor external supply voltages of typically 2.5V, 3.3V, and 12V, 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. All inputs are converted to an 8-bit code using an ADC with an oversampling ratio of 8 to improve noise rejection. The oversampling ratio can be reduced by a factor of 4, with a corresponding reduction in the monitoring cycle time, by setting bit 5 of the configuration register to 1. Each input voltage is scaled down by an on-chip resistive divider so that its output, at the nominal input voltage, is 3/4 of the ADC's fullscale range, or a decimal count of 192 (Table 3). Table 1 is the register map and Table 2 is the temperature data format.
MAX6652
Table 1. Register Map
ADDRESS READ/WRITE POWER-ON DEFAULT DESCRIPTION
20h 21h 22h 23h 27h 2Bh 2Ch 2Dh 2Eh 2Fh 30h 31h 32h 39h 3Ah 40h 41h 43h
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
-- -- -- -- -- 1101 0011 (1.1 2.5V) 1010 1101 (0.9 2.5V) 1101 0011 (1.1 12V) 1010 1101 (0.9 12V) 1101 0011 (1.1 3.3V) 1010 1101 (0.9 3.3V) 1101 0011 (1.1 5V) 1010 1101 (0.9 5V) 0101 0000 (+80C) 0100 0001 (+65C) 0000 1000 0000 0000 0000 0000
Data register for 2.5 VIN measurement Data register for 12VIN measurement Data register for 3.3VIN measurement Data register for VCC measurement Data register for temperature measurement High limit for 2.5VIN Low limit for 2.5VIN High limit for 12VIN Low limit for 12VIN High limit for 3.3VIN Low limit for 3.3VIN 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 7bit chip address is read back from the serial address register, an 8-bit word will be presented with a 0 in bit 0 (Y). Temperature configuration register
48h
R/W
0010 1XXY
4Bh
R/W
0000 0000
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Temperature Sensor and System Monitor in a 10-Pin MAX
Table 2. Temperature Data Format
TEMPERATURE (C) +125 +25 +1 0 -1 -25 -40 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
corresponding interrupt status bit (bits 0 through 4) to 1 (Table 5). The interrupt will be 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. Unless the fault is removed, the ALERT output will only remain cleared until the end of the next conversion cycle where it will again be 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 0.
MAX6652
ADC and Multiplexer
Writing a 1 to bit 0 of the configuration register starts the monitoring function. The device will perform a sequential sampling of all the inputs, starting with the internal temperature sensor and continuing with 2.5VIN, 12VIN, 3.3VIN, and VCC. If the master terminates the conversion, the sequential sampling will not stop until the sampling cycle is completed and the results are stored. When it starts again, it will always start 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 will cause the open-drain output (ALERT) to go to the active-low state and set each 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 voltage. This is equivalent to 4 and 2 cycles of 60Hz, respectively, and provides protection against noise pickup from the main supply. The internal oscillation 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.
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 12VIN 62mV (12V/192) < 62mV 62mV - 125mV 125mV - 187mV -- 4.000V - 4.063V -- 8.000V - 8.063V -- 12.000V - 12.063V -- 15.813V - 15.875V 15.875V - 15.938V > 15.938 INPUT VOLTAGE AT 2.5VIN 13mV (2.5V/192) < 13mV 13mV - 26mV 26mV - 39mV -- 833mV - 846mV -- 1.667V - 1.680V -- 2.500V - 2.513V -- 3.294V - 3.307V 3.572V - 3.586V > 3.586 INPUT VOLTAGE AT 3.3VIN 17.2mV (3.3V/192) < 17.2mV 17.2mV - 34.4mV 34.4mV - 51.6mV -- 1.100V - 1.117V -- 2.200V - 2.217V -- 3.300V - 3.317V -- 4.348V - 4.366V 4.366V - 4.383V > 4.383 VCC 26mV (5.0V/192) -- -- -- -- -- -- 3.330V - 3.560V -- 5.000V - 5.026V -- 6.566V - 6.615V 6.615V - 6.640V > 6.640
6
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Temperature Sensor and System Monitor in a 10-Pin MAX MAX6652
Table 4. Configuration Register (Address 41h, Power-Up Default = 00h)
BIT NAME READ/WRITE DESCRIPTION This bit controls the monitoring loop. Setting the bit to 0 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 interrupt output. Setting the bit to 1 enabes the interrupt output; setting the bit to 0 disables the interrupt output. -- This bit is used to clear the interrupt output when it is set to high. It will not affect the interrupt status register. The monitoring loop will not start until the bit is set to 0. 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 rate by a factor of four when it is set to 1. -- This bit is used as a reset signal for the register initialization. The 1 of this bit will reset all the register values into the power-up default mode, including bit 7 itself.
0
Start/Stop
R/W
1 2 3
Interrupt Enable Reserved Interrupt 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 12VIN Error 3.3VIN 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 12VIN input. A 1 indicates either a high or low limit has been exceeded at the 3.3VIN 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 will generate and clear this bit depend on the temperature interrupt mode selected by bits 0 and 1 in the temperature configuration register. --
4
Temperature Error
R
5, 6, 7
Reserved
--
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Temperature Sensor and System Monitor in a 10-Pin MAX MAX6652
Table 6. Interrupt Mask Register (Address 43h, Power-Up Default = 00h)
BIT 0 1 2 3 4 5, 6, 7 NAME 2.5V 12V 3.3V 5.0V Temperature 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 12VIN input. Setting the bit to 1 disables the interrupt status register bit (bit 2) and the ALERT output for the 3.3VIN 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. --
Low-Power Shutdown Mode
Setting bit 0 in the configuration register to 0 stops the monitoring loop and puts the MAX6652 into low-power 2 shutdown mode. In this mode, the I C-compatible/ SMBus interface remains active, and the supply current drops to 10A or less.
Power-On Reset (POR)
The MAX6652 power-on reset supply (POR) voltage is typically 2V. Below this supply voltage, all registers are reset, the device is put into shutdown mode, and the 2 I C-compatible/SMBus interface is inactive.
(Table 5). Bits 0 through 3 correspond to the 2.5V, 12V, 3.3V, and 5V internal VCC voltage inputs, and bit 4 corresponds to the temperature. If a threshold has been crossed, the appropriate bit will contain 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.
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, and comparator modes. The ALERT signal can be cleared only by reading the interrupt status register (Table 5), except when the ALERT has been activated by an out-of-range temperature in comparator mode. In this case, ALERT is only cleared when the fault is removed. Reading the interrupt status register also clears this register, except for bit 4 in comparator mode. Unless the fault is removed, ALERT will be 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 0. The interrupt does not halt conversions. New temperature and voltage data continue to be available over the I2C-compatible/SMBus interface after ALERT is asserted. The three temperature ALERT modes are illustrated 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.
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). 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, respectively.
Interrupt Status Byte Functions
The interrupt status register records temperature or voltage fault conditions whenever a limit is exceeded
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Temperature Sensor and System Monitor in a 10-Pin MAX
Default Mode An interrupt is initiated when temperature exceeds THOT (address 39Ah). The interrupt is cleared only by reading the interrupt status register. An interrupt will continue to be generated on subsequent measurements until temperature goes below THYST (address 3Ah). One-Time Interrupt Mode An interrupt is initiated when temperature exceeds THOT (address 39Ah). 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 39Ah). The ALERT output will remain asserted low until the temperature goes below THOT. Reading the interrupt status register will not clear the ALERT output or interrupt status bit in the register. The interrupt will continue to be generated on subsequent measurements until temperature falls below THOT. Figure 1 shows successive interrupts and clears using a temperature fault as an example. devices are wired-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 1000). 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 2 devices simultaneously, similar to the I C 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 MAX6652 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 0 before it can identify other slaves generating an interrupt.
MAX6652
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 MAX6652. The functions of those other registers are described below.
I2C-Compatible/SMBus Digital Interface
From a software perspective, the MAX6652 appears as a set of byte-wide registers that contain voltage and temperature data, alarm threshold values, or control bits. The device employs four standard I 2C-compatible/ SMBus protocols: write byte, read byte, send byte, and receive byte (Figures 2, 3, 4).
Configuration Byte Functions
The configuration register (Table 4) is a read-write register with several functions: Bit 0 puts the MAX6652 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 will 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 0. 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.
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 MAX6652 can reside on the same bus without address conflicts (Table 1). The address pin state is checked at the beginning of each I2C-compatible/SMBus transaction and so is insensitive to glitches on VCC. Any address code can also be written to the serial address register and will overwrite the code set by connecting the ADD pin until the MAX6652 is taken through a POR cycle. The MAX6652 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
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Temperature Sensor and System Monitor in a 10-Pin MAX MAX6652
Table 7. Temperature Configuration Register
BIT NAME R/W Bit 1, Bit 0 Bit 1, Bit 0 Bit 1, Bit 0 Bit 1, Bit 0 -- DESCRIPTION 00: Default Mode 01: One-Time Interrupt Mode 10: Comparator Mode 11: Default Mode
0-1
Hot Temperature Interrupt Mode Select Reserved
R/W
2-7
R/W
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
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 will also reset bit 7 to its power-up value of 0.
Applications Information
Sensing Circuit Board and Component Temperatures
Temperature sensor ICs like the MAX6652 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 MAX6652 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 will maximize the heat transfer from the component to the sensor.
10
The thermal path between the plastic package and the die is not as good as the path through the leads, so the MAX6652, like all temperature sensors in plastic packages, will be less sensitive to the temperature of the surrounding air than to the temperature of the leads. As with any IC, the wiring and circuits must be kept insulated and dry to avoid leakage and corrosion, especially if the part will be operated at cold temperatures where condensation can occur.
Chip Information
TRANSISTOR COUNT: 13,446 PROCESS: BiCMOS
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Temperature Sensor and System Monitor in a 10-Pin MAX MAX6652
Write Byte Format S ADDRESS 7 bits Slave Address: equivalent to chip-select line of a 3-wire interface Read Byte Format S ADDRESS 7 bits Slave Address: equivalent to chip-select line WR ACK COMMAND 8 bits Command Byte: selects which register you are reading from ACK S ADDRESS 7 bits Slave Address: repeated due to change in dataflow direction Receive Byte Format ACK COMMAND 8 bits Data Byte: writes data to the register commanded by the last read byte or write byte transmission S = Start condition P = Stop condition Shaded = Slave transmission A = Not acknowledged ACK P S ADDRESS 7 bits RD ACK DATA 8 bits 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 A P RD ACK DATA 8 bits Data Byte: reads from the register set by the command byte A P WR 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
Send Byte Format S ADDRESS 7 bits WR
Figure 2. I 2C/SMBus Protocols
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 = MASTER PULLS DATA LINE LOW
J = ACKNOWLEDGE CLOCKED INTO SLAVE K = ACKNOWLEDGE CLOCK PULSE L = STOP CONDITION M = NEW START CONDITION
Figure 3. I 2C/SMBus Write Timing Diagram ______________________________________________________________________________________ 11
Temperature Sensor and System Monitor in a 10-Pin MAX MAX6652
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 MASTER H = LSB OF DATA CLOCKED INTO MASTER I = MASTER PULLS DATA LINE LOW
J = ACKNOWLEDGE CLOCKED INTO SLAVE K = ACKNOWLEDGE CLOCK PULSE L = STOP CONDITION M = NEW START CONDITION
Figure 4. I 2C/SMBus Read Timing Diagram
Typical Application Circuit
3.3V VCC CPU 0.1F TO 12V TO 2.5V TO 3.3V 12VIN 2.5VIN 3.3VIN MAX6652 N.C. GND VCC SCL SDA ADD ALERT 10k I2C/SMBus CONTROLLER
Functional Diagram
VCC
MAX6652 12VIN 2.5VIN 3.3VIN INPUT VOLTAGE SCALING AND MULTIPLEXER ADC DATA AND CONTROL LOGIC
TEMPERATURE SENSOR
VOLTAGE REFERENCE
I2C/SMBusCOMPATIBLE INTERFACE
SDA SCL ALERT ADD
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.
12 ____________________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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