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19-1841; Rev 2; 7/02
9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23
General Description
The MAX6625/MAX6626 combine a temperature sensor, a programmable overtemperature alarm, and an I2CTMcompatible serial interface into single compact packages. They convert their die temperatures into digital values using internal analog-to-digital converters (ADCs). The result of the conversion is held in a temperature register, readable at any time through the serial interface. A dedicated alarm output, OT, activates if the conversion result exceeds the value programmed in the high-temperature register. A programmable fault queue sets the number of faults that must occur before the alarm activates, preventing spurious alarms in noisy environments. OT has programmable output polarity and operating modes. The MAX6625/MAX6626 feature a shutdown mode that saves power by turning off everything but the power-on reset and the I2C-compatible interface. Four separate addresses can be configured with the ADD pin, allowing up to four MAX6625/MAX6626 devices to be placed on the same bus. The MAX6625P/MAX6626P OT outputs are open drain, and the MAX6625R/MAX6626R OT outputs include internal pullup resistors. The MAX6625 has a 9-bit internal ADC and can function as a replacement for the LM75 in most applications. The MAX6626 has a 12-bit internal ADC. Both devices come in the space-saving 6-pin SOT23 package.
Features
o 9-Bit Temperature-to-Digital Converter (MAX6625) o 12-Bit Temperature-to-Digital Converter (MAX6626) o Accuracy 1C (TA = +25C) 1.5C (0C to +50C) 2C (0C to +70C) 3C (-40C to +85C) 4C (-55C to +125C) o 133ms Conversion Time o I2C-Compatible Serial Interface o Up to Four Devices on a Single Bus o Versatile Alarm Output with Programmable Trip Temperature and Hysteresis o Low-Power Shutdown Mode o Space-Saving 6-Pin SOT23 Package
MAX6625/MAX6626
Ordering Information
PART MA X6 62 5PMUT -T * MAX6625RMUT-T* MA X6 62 6PMUT -T * MAX6626RMUT-T* TEMP. RANGE -55C to +125C -55C to +125C -55C to +125C -55C to +125C PIN-PACKAGE 6 SOT23-6 6 SOT23-6 6 SOT23-6 6 SOT23-6
Applications
Fan Control Temperature Alarms System Temperature Control Industrial Equipment
*For device options, see Selector Guide at end of data sheet. Requires special solder temperature profile described in the Absolute Maximum Ratings section.
Typical Operating Circuit
VS 1k 0.1F 6 4 1k 10k (OMIT FOR MAX6625R AND MAX6626R) OT OUTPUT
Pin Configuration
TOP VIEW
SDA 1 6 VS
MAX6625 MAX6626
1 3
SDA SCL TO I2C MASTER
GND 2
MAX6625 MAX6626
5
ADD
SCL 3
5 2
4
OT
SOT23-6
I2C is a trademark of Philips Corp. ________________________________________________________________ Maxim Integrated Products 1
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9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 MAX6625/MAX6626
ABSOLUTE MAXIMUM RATINGS
VS to GND ................................................................-0.3V to +6V OT, SCL, SDA to GND.............................................-0.3V to +6V ADD to GND .................................................-0.3V to (VS + 0.3V) Current into Any Pin............................................................5mA OT Sink Current.................................................................. 20mA Continuous Power Dissipation 6-Pin SOT23 (derate 9.1mW/C above +70C)............727mW Junction Temperature ......................................................+150C Storage Temperature Range .............................-60C to +150C Lead Temperature .............................................................Note 1 ESD Rating (Human Body Model)......................................2000V
Note 1: This device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile the device can be exposed to during board-level solder attach and rework. This limit permits only the use of the solder profiles recommended in the industry-standard specification, IPC/JEDEC J-STD-020A, paragraph 7.6, Table 3 for IR/VPR and Convection Reflow. Preheating is required. Hand or wave soldering is not allowed.
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
(+3V VS +5.5V, TA = -55C to +125C, unless otherwise noted.)
PARAMETER Power-Supply Voltage Quiescent Current SYMBOL VS I2C-compatible active IC I2C-compatible inactive Shutdown mode ADC Resolution Temperature Resolution MAX6625 MAX6626 MAX6625 MAX6626 TA = +25C, VS = +3V to +3.6V 0C = TA +50C, VS = +3.0V to +3.6V 0C = TA +70C, VS = +3.0V to +3.6V Power-Supply Sensitivity Conversion Time OT Pullup Resistor OT Saturation Voltage (Note 4) OT Delay THIGH Default Temperature TLOW Default Temperature THIGH TLOW VS < +3.6V VS > +3.6V 2 3 0.8 0.2 tC RP VL MAX6625R, MAX6626R only IOUT = 4mA (Programmable through fault queue) 1 x tC 80 75 25 VS = +3V to +5.5V 1 133 50 0.8 6 x tC 250 1 9 12 0.5 0.0625 1 1.5 2.0 C/V ms k V ms C C C CONDITIONS MIN 3 TYP MAX 5.5 1 UNITS V mA A A Bits C/LSB
Accuracy (Notes 2, 3)
I2C-COMPATIBLE I/O: SCL, SDA, ADD Input High Voltage Input Low Voltage Input Hysteresis VIH VIL V V V
2
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9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 MAX6625/MAX6626
ELECTRICAL CHARACTERISTICS (continued)
(+3V VS +5.5V, TA = -55C to +125C, unless otherwise noted.)
PARAMETER Input High Leakage Current Input Low Leakage Current Input Capacitance Output Low Voltage Output High Current I2C-COMPATIBLE TIMING Serial Clock Frequency Bus Free Time Between STOP and START Conditions START Condition Hold Time STOP Condition Setup Time Clock Low Period Clock High Period Data Setup Time Data Hold Time (Note 5) Maximum Receive SCL/SDA Rise Time (Note 6) Minimum Receive SCL/SDA Rise Time (Note 6) Maximum Receive SCL/SDA Fall Time (Note 6) Minimum Receive SCL/SDA Fall Time (Note 6) Transmit SDA Fall Time (Note 6) Pulse Width of Suppressed Spike (Note 7) fSCL tBUF tHD:STA tSU:STO tLOW tHIGH tSU:DAT tHD:DAT tR tR tF tF tF tSP CB = 400pF, IO = 3mA 20 + 0.1CB 50 DC 1.3 0.6 0.6 1.3 0.6 100 0 300 20 + 0.1CB 300 20 + 0.1CB 250 0.9 400 kHz s s s s s ns s ns ns ns ns ns ns SYMBOL IIH IIL CIN VOL IOH IOL = 3mA VOH = 5V VIN = +5V VIN = 0 10 0.4 1 CONDITIONS MIN TYP MAX 1 1 UNITS A A pF V A
Note 2: Guaranteed by design and characterization to 5 sigma. Note 3: Quantization error not included in specifications for temperature accuracy. Note 4: Output current should be minimized for best temperature accuracy. Power dissipation within the MAX6625/MAX6626 will cause self-heating and temperature drift; see Thermal Considerations section. Note 5: A master device must provide a hold time of at least 300ns for the SDA signal in order to bridge the undefined region of SCL's falling edge. Note 6: CB = total capacitance of one bus line in pF. Tested with CB = 400pF. Note 7: Input filters on SDA, SCL, and ADD suppress noise spikes less than 50ns.
SCL tF tLOW tR tHIGH tHD:STA SDA tBUF tSU:DAT tHD:DAT tSU:STO
Figure 1. Serial Bus Timing _______________________________________________________________________________________ 3
9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 MAX6625/MAX6626
Typical Operating Characteristics
(VS = +3.3V, TA = +25C, unless otherwise noted.)
RESPONSE TO THERMAL SHOCK TEMPERATURE vs. TIME
MAX6625 toc01
STATIC QUIESCENT SUPPLY CURRENT vs. TEMPERATURE
MAX6625 toc02
100
200 180 INPUT CURRENT (A) 160 140 120 100 80
OUTPUT TEMPERATURE (C)
80
60
40
20 DEVICE IMMERSED IN +85C FLUORINERT BATH 0 -5 0 5 10 TIME (s) 15 20
-55
-25
5
35
65
95
125
TEMPERATURE (C)
DYNAMIC QUIESCENT SUPPLY CURRENT vs. TEMPERATURE
MAX6625 toc03
TEMPERATURE ERROR vs. TEMPERATURE
4 TEMPERATURE ERROR (C) 3 2 1 0 -1 -2 -3 -4 MINIMUM LIMIT 5 SIGMA RANGE
MAX6625 toc04
200 180 INPUT CURRENT (A) 160 140 120 100 80 -55 -25 5 35 65 95
5 MAXIMUM LIMIT
-5 125 -50 -25 0 25 50 75 100 125 TEMPERATURE (C) TEMPERATURE (C)
Pin Description
PIN 1 2 3 4 5 6 NAME SDA GND SCL OT ADD VS I2C-Compatible Serial Bidirectional Data Line Power-Supply Ground I2C-Compatible Clock Input Temperature Alarm Output I2C-Compatible Address Set Pin: Ground (0), VS (1), SDA (2), SCL (3); see Table 1. Power-Supply Input, +3V to +5.5V. Bypass VS to GND with a 0.1F capacitor. FUNCTION
4
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9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23
Detailed Description
The MAX6625/MAX6626 continuously convert their die temperatures into digital values using their self-contained delta-sigma ADCs. The resulting data is readable at any time through the I 2 C-compatible serial interface. A dedicated alarm output asserts if the result exceeds the value in the programmable high-temperature register. A programmable fault queue sets the number of faults that must occur before the alarm asserts, preventing spurious alarms in noisy environments. The alarm output polarity is selectable and deasserts based on either of two operating modes, comparator or interrupt. In comparator mode, the OT output deasserts if the temperature conversion result falls below the programmable low-temperature register value (subject to the fault queue conditions) providing adjustable hysteresis. In interrupt mode, the OT output deasserts when any register is read through the serial interface. Each conversion cycle takes about 130ms. At power-up, the temperature register is set to 8000H until the first conversion is completed. The MAX6625/MAX6626 feature a shutdown mode, accessible through the serial interface, that saves power by turning off everything but the power-on reset and the I2C-compatible interface. While in shutdown mode the temperature register is set to 8000H. The device func-
MAX6625/MAX6626
tions as a slave on the I2C-compatible bus supporting Write Byte, Write Word, Read Byte, and Read Word commands. Four separate addresses can be configured with the ADD pin, allowing up to four MAX6625/MAX6626 devices to be placed on the same bus. Figure 2 shows the functional block diagram of the MAX6625/MAX6626.
Serial interface
I2C-Compatible Operation The MAX6625/MAX6626 are readable and programmable through their I 2 C-compatible serial interface. Figures 3 and 4 show the timing details of the clock (SCL) and data (SDA) signals. The device functions as a slave on the I2C-compatible bus and supports Write Byte, Write Word, Read Byte, and Read Word commands. Addressing Four separate addresses can be configured with the ADD pin, allowing up to four MAX6625/MAX6626s to be placed on the same bus. The address is selected by connecting the ADD pin to either of four places: GND (address 0), VS (address 1), SDA (address 2), or SCL (address 3). Table 1 shows the full I 2C-compatible address for each state.
BANDGAP REGISTER
REFERENCE ADC TEMP SIGNAL
MAX6625 MAX6626
+Vs
TEMPERATURE REGISTER SET-POINT COMPARATOR
MAX665_ R ONLY
ADDRESS POINTER REGISTER
THIGH REGISTER
OT TLOW REGISTER
CONFIGURATION REGISTER
FAULT QUEUE COUNTER GND SDA SCL ADD
SERIAL BUS INTERFACE
Figure 2. Functional Block Diagram
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5
MAX6625/MAX6626
9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23
6
ADDRESS BYTE POINTER BYTE ADDRESS BYTE DATA BYTE (a) TYPICAL POINTER SET FOLLOWED BY IMMEDIATE READ FROM CONFIGURATION REGISTER ACK BY MAX6625 ACK BY MAX6625 ACK BY REPEAT MAX6625 START BY MASTER NO ACK BY MASTER STOP COND BY MASTER ADDRESS BYTE CONFIGURATION BYTE (b) CONFIGURATION REGISTER WRITE ACK BY MAX6625 POINTER BYTE ACK BY MAX6625 STOP COND BY ACK BY MASTER MAX6625 ADDRESS BYTE POINTER BYTE ACK BY MAX6625 ACK BY MAX6625 STOP COND BY MASTER MOST-SIGNIFICANT DATA BYTE ACK BY MAX6625 LEAST-SIGNIFICANT DATA BYTE ACK BY MAX6625 (c) THIGH AND TLOW WRITE
Figure 3. I2C-Compatible Timing Diagram
START BY MASTER
START BY MASTER
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START BY MASTER
STOP COND BY MASTER ADDRESS BYTE (a) TYPICAL 2-BYTE READ FROM PRESET POINTER LOCATION SUCH AS TEMP, THIGH, TLOW ACK BY MAX6625 MOST-SIGNIFICANT DATA BYTE LEAST-SIGNIFICANT DATA BYTE ACK BY MASTER NO ACK BY MASTER
Figure 4. I2C-Compatible Timing Diagram
ACK BY MASTER POINTER BYTE ACK BY MAX6625 STOP COND BY MASTER ACK BY MASTER LEAST-SIGNIFICANT DATA BYTE NO ACK BY MASTER ADDRESS BYTE ACK BY MAX6625 MOST-SIGNIFICANT DATA BYTE (b) TYPICAL POINTER SET FOLLOWED BY IMMEDIATE READ FOR 2-BYTE REGISTER SUCH AS TEMP, THIGH, TLOW STOP COND BY MASTER DATA BYTE NO ACK BY MASTER ADDRESS BYTE ACK BY MAX6625 (c) TYPICAL 1-BYTE READ FROM CONFIGURATION REGISTER WITH PRESET POINTER
START BY MASTER
START BY MASTER
ADDRESS BYTE
REPEAT START BY MASTER
9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23
MAX6625/MAX6626
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START BY MASTER
7
9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 MAX6625/MAX6626
SDA INTERFACE SCL DATA ADDRESS
POINTER REGISTER (SELECTS REGISTER FOR COMMUNICATION) REGISTER SELECT TEMPERATURE (READ ONLY) POINTER = 00000000 CONFIGURATION (READ-WRITE, SETS OPERATING MODES) POINTER = 00000001
THIGH SET-POINT (READ-WRITE) POINTER = 00000011
TLOW SET-POINT (READ-WRITE) POINTER = 00000010
Figure 5. MAX6625/MAX6626 Programmers Model
Table 1. Address Selection
ADD CONNECTION GND VS SDA SCL I2C-COMPATIBLE ADDRESS 100 1000 100 1001 100 1010 100 1011
the overtemperature alarm. The low-temperature register is 9 bits, read/write, and contains the value to which the temperature must fall before the overtemperature alarm is deasserted, if in comparator mode.
Temperature Conversion
An on-chip bandgap reference produces a signal proportional to absolute temperature (PTAT), as well as the temperature-stable reference voltage necessary for the analog-to-digital conversion. The PTAT signal is digitized by the on-board ADC to a resolution of 0.5C for the MAX6625, and 0.0625C for the MAX6626. The resulting digital value is placed in the temperature register. The temperature conversion runs continuously and asynchronously from the I2C-compatible interface at a rate of 133ms per conversion. When the temperature register is read, the most recently completed conversion result is provided and the currently active conversion is aborted. When the bus transaction is finished by an I2C-compatible stop condition conversions resume.
Control Registers Five registers control the operation of the MAX6625/ MAX6626 (Figure 5 and Tables 2 through 7). The pointer register should be the first addressed and determines which of the other four registers will be acted on. The other four are the temperature, configuration, hightemperature (THIGH), and low-temperature (TLOW) registers. The temperature register is 9 bits for the MAX6625 and 12 bits for the MAX6626, read only, and contains the latest temperature data. The register length is 16 bits with the unused bits masked to 0. The digital temperature data contained in the temperature register is in C, using a two's-complement format with 1LSB corresponding to 0.5C for the MAX6625 and 0.0625C for the MAX6626 (Table 8). The configuration register is 8 bits, read/write, and contains the fault queue depth, the temperature alarm polarity select bit, the interrupt mode select bit, and the shutdown control bit. The high-temperature register is 9 bits, read/write, and contains the value that triggers
8
Overtemperature Alarm
The dedicated overtemperature output pin, OT, has programmable polarity and two modes: comparator and interrupt. Polarity and mode are selected through the configuration register, and alarm activity is governed by a fault queue. Fault queue depth is also selected through the configuration register (Tables 5 and 6). The MAX6625P/MAX6626P OT output is open
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9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 MAX6625/MAX6626
Table 2. Pointer Register
D7 0 D6 0 D5 0 D4 0 D3 0 D2 0 D1 D0 Register select (see Table 3)
D7 to D2: Will read all zeros, cannot be written.
Table 3. Register Select
D1 0 0 1 1 D0 0 1 0 1 Configuration TLOW THIGH REGISTER Temperature (Default)
Table 4. Temperature Register
PART MAX6625 MAX6625 D15 MSB (Sign) MSB (Sign) D14 Bit 7 Bit 11 D13 Bit 6 Bit 10 D12 Bit 5 Bit 9 D11 Bit 4 Bit 8 D10 Bit 3 Bit 7 D9 Bit 2 Bit 6 D8 Bit 1 Bit 5 D7 LSB Bit 4 D6 0 Bit 3 D5 0 Bit 2 D4 0 Bit 1 D3 0 LSB D2-D0 0 0
D6 to D0, MAX6625: Will read all zeros, cannot be written. D2 to D0, MAX6626: Will read all zeros, cannot be written. D15: MSB is the sign bit.
1LSB = 0.5C for the MAX6625. 1LSB = 0.0.0625C for the MAX6626. Temperature is stored in two's-complement format.
Table 5. Configuration Register
D7 0 D6 0 D5 0 D4 D3 D2 OT Polarity D1 Comparator or Interrupt Mode D0 Shutdown Fault Queue Depth
Table 6. Fault Queue Depth
D4 0 0 1 1 D3 0 1 0 1 NUMBER OF FAULTS 1 (Default) 2 4 6
All defaults = 0. D0: 0 = Normal operation, 1 = Shutdown. D1: 0 = Comparator mode, 1 = Interrupt mode. D2: 0 = Active low, 1 = Active high. D7 to D5: Reserved locations, always write zeros.
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9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 MAX6625/MAX6626
Table 7. THIGH and TLOW Registers
D15 MSB D14 Bit 7 D13 Bit 6 D12 Bit 5 D11 Bit 4 D10 Bit 3 D9 Bit 2 D8 Bit 1 D7 LSB D6 0 D5 0 D4 0 D3 0 D2 0 D1 0 D0 0
D6 to D0: Will read all zeros, cannot be written. D15: MSB is the sign bit. Default: THIGH = +80C (5000H), TLOW = +75C (4B00H). LSB = 0.5C.
Table 8. Output Code vs. Temperature
DIGITAL OUTPUT CODE TEMPERATURE (C) MSB +125.0000 +124.9375 +25.0000 +0.5000 0.0000 -0.5000 -25.0000 -55.0000 MAX6625 BINARY LSB 0111 1101 0000 0000 0111 1100 1000 0000 0001 1001 0000 0000 0000 0000 1000 0000 0000 0000 0000 0000 1111 1111 1000 0000 1110 0111 0000 0000 1100 1001 0000 0000 1000 0000 0000 0000 HEX 7D00 7C80 1900 0080 0000 FF80 E700 C900 8000 BINARY MSB LSB 0111 1101 0000 0000 0111 1100 1111 0000 0001 1001 0000 0000 0000 0000 1000 0000 0000 0000 0000 0000 1111 1111 1000 0000 1110 0111 0000 0000 1100 1001 0000 0000 1000 0000 0000 0000 MAX6626 HEX 7D00 7CF0 1900 0080 0000 FF80 E700 C900 8000
*8000H is the default value at power-up and after coming out of shutdown.
10
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9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 MAX6625/MAX6626
THIGH DIE TEMPERATURE
TLOW
OT (COMPARATOR MODE)
OT (INTERRUPT MODE)
*
*
*
*THIS ASSUMES DEASSERTION OF OT BY A MASTER THROUGH THE SERIAL INTERFACE. SEE INTERRUPT MODE SECTION.
TEMPERATURE RESPONSE SHOWN WITH OT SET FOR ACTIVE LOW TIME
Figure 6. OT Alarm Output and Reset Diagram
drain, and the MAX6625R/MAX6626R output includes an internal 35k (typ) pullup resistor. Figure 6 shows the OT alarm operation and reset details. Fault Queue A programmable fault queue on the MAX6625/ MAX6626 eliminates spurious alarm activity in noisy environments. The queue sets the number of consecutive out-of-tolerance temperature readings that must occur before the OT alarm output is toggled. An out-oftolerance reading is above THIGH or below TLOW. The fault queue depth defaults to one at power-up and may be programmed to one, two, four, or six consecutive conversions. Any time the conversion result is in tolerance, and OT is not asserted, the queue is cleared, even if it contains some out-of-tolerance counts. Additionally, the fault queue automatically clears at power-up, in shutdown, or if a master writes to any of the THIGH, TLOW, or configuration registers. Whenever the fault queue is cleared, OT is deasserted. For example, the fault queue is set to four, two consecutive out-of-tolerance readings have occurred, and the master writes to the TLOW register. The fault queue is cleared and begins to look for four new consecutive out-of-tolerance conversions. Comparator Mode In comparator mode, OT is asserted when the number of consecutive conversions exceeding the value in the THIGH register is equal to the depth of the fault queue.
OT deasserts when the number of consecutive conversions less than the value in the TLOW register is equal to the depth of the fault queue. THIGH minus TLOW is the effective hysteresis of the OT output. For example, if THIGH is set to +100C, TLOW is set to +80C, and the fault queue depth is set to four, OT will not assert until four consecutive conversions exceed +100C. Then, OT will not deassert until four consecutive conversions are less than +80C. Comparator mode allows autonomous clearing of an OT fault without the intervention of a master and is ideal to use for driving a cooling fan (Figure 7). Interrupt Mode In interrupt mode, the MAX6625/MAX6626 look for a THIGH or a TLOW fault based on previous fault activity. The OT pin asserts an alarm for an undertemperature fault, as well as for an overtemperature fault, depending on certain conditions. If the fault queue is cleared at power-up, the IC looks for a THIGH fault. After a THIGH fault, the IC looks for a TLOW fault. After a TLOW fault, the IC looks for a THIGH fault, and it will bounce back and forth if properly deasserted each time. Once either fault has occurred, it remains active indefinitely until deasserted by a read of any register, and the device then begins to look for a fault of the opposite type. Also, if the fault queue is cleared, OT is deasserted and the IC once again looks for a THIGH fault. The activation of any fault is subject to the depth of the fault queue.
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9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 MAX6625/MAX6626
Example 1: If THIGH is set to +100C, TLOW is set to +80C, and the fault queue depth is set to four, OT will not assert until four consecutive conversions exceed +100C. If the temperature is then read through the I 2 C-compatible interface, OT will deassert. OT will assert again when four consecutive conversions are less than +80C. Example 2: If THIGH is set to +100C, TLOW is set to +80C, and the fault queue depth is set to four, OT will not assert until four consecutive conversions exceed +100C. If the T HIGH register is then changed to +120C, OT deasserts and the IC looks for a new THIGH fault. key to accurate temperature monitoring is good thermal contact between the MAX6625/MAX6626 package and the monitored device or circuit. In some applications, the SOT23-6 package may be small enough to fit underneath a socketed P, allowing the device to monitor the P's temperature directly. Heat flows in and out of plastic packages primarily through the leads. Short, wide copper traces leading to the temperature monitor ensure that heat transfers quickly and reliably. The rise in die temperature due to self-heating is given by the following formula: TJ = PD JA where PD is the power dissipated by the MAX6625/ MAX6626, and JA is the package's thermal resistance. The typical thermal resistance is +110C/W for the SOT23-6 package. To limit the effects of self-heating, minimize the output currents. For example, if the MAX6625/MAX6626 sink 4mA with the maximum OT VL spec of 0.8V, an additional 3.2mW of power is dissipated within the IC. This corresponds to a 0.35C rise in the die temperature.
Shutdown
The MAX6625/MAX6626 offer a low-power shutdown mode. Enter shutdown mode by programming the shutdown bit of the control register high. In shutdown, the temperature register is set to 8000H and the ADC is turned off, reducing the device current draw to 1A (typ). After coming out of shutdown, the temperature register will continue to read 8000H until the first conversion result appears. The fault queue is held in reset during shutdown.
Thermal Considerations
The MAX6625/MAX6626 supply current is less than 1mA when the I2C-compatible interface is active. When used to drive high-impedance loads, the devices dissipate negligible power; therefore, the die temperature is essentially the same as the package temperature. The
Applications
Figure 7 shows the MAX6625/MAX6626 used as a temperature-triggered fan controller. Figure 8 shows the MAX6625/MAX6626 used as a thermostat to control a heating element.
+VS +3V TO +5V
+VS +3V to +5V +12V HEATER
6 4 OT
12V 300mA FAN MOTOR LOGIC LEVEL MOSFET 6 4k RELAY 5VDC, 20mA 125VAC, 1A
MAX6625R MAX6626R
MAX6625P MAX6626P
OT 5 2N3904 HEATER SUPPLY 3
2
Figure 7. Fan Controller 12
Figure 8. Simple Thermostat
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9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23
Selector Guide
PART MAX6625PMUT MAX6625RMUT MAX6626PMUT MAX6626RMUT ALARM OUTPUT Open Drain Internal Pullup Open Drain Internal Pullup RESOLUTION (bits) 9 9 12 12 TOP MARK AAHY AAHZ AANP AANQ
Chip Information
TRANSISTOR COUNT: 7513 PROCESS: BiCMOS
MAX6625/MAX6626
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.)
6LSOT.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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13 (c) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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