19-1841; Rev 2; 7/02 9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 Features ♦ 9-Bit Temperature-to-Digital Converter (MAX6625) 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. ♦ Up to Four Devices on a Single Bus Applications Fan Control Temperature Alarms System Temperature Control Industrial Equipment ♦ 12-Bit Temperature-to-Digital Converter (MAX6626) ♦ Accuracy ±1°C (TA = +25°C) ±1.5°C (0°C to +50°C) ±2°C (0°C to +70°C) ±3°C (-40°C to +85°C) ±4°C (-55°C to +125°C) ♦ 133ms Conversion Time ♦ I2C-Compatible Serial Interface ♦ Versatile Alarm Output with Programmable Trip Temperature and Hysteresis ♦ Low-Power Shutdown Mode ♦ Space-Saving 6-Pin SOT23 Package Ordering Information PART TEMP. RANGE MA X6 62 5PMUT -T * -55°C to +125°C PIN-PACKAGE 6 SOT23-6 MAX6625RMUT-T* -55°C to +125°C 6 SOT23-6 MA X6 62 6PMUT -T * -55°C to +125°C 6 SOT23-6 MAX6626RMUT-T* -55°C to +125°C 6 SOT23-6 *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 Pin Configuration VS 1k 0.1µF 6 4 TOP VIEW 1k 10k (OMIT FOR MAX6625R AND MAX6626R) SDA 1 OT OUTPUT MAX6625 MAX6626 1 3 GND 2 SDA SCL MAX6625 MAX6626 2 VS 5 ADD 4 OT TO I2C MASTER SCL 3 5 6 SOT23-6 I2C is a trademark of Philips Corp. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX6625/MAX6626 General Description The MAX6625/MAX6626 combine a temperature sensor, a programmable overtemperature alarm, and an I2C™compatible 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. MAX6625/MAX6626 9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 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 +70°C)............727mW Junction Temperature ......................................................+150°C Storage Temperature Range .............................-60°C to +150°C 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 = -55°C to +125°C, unless otherwise noted.) PARAMETER Power-Supply Voltage SYMBOL CONDITIONS VS MIN TYP 3 I2C-compatible active Quiescent Current IC ADC Resolution I2C-compatible inactive Power-Supply Sensitivity 1 mA µA 1 µA MAX6625 9 MAX6626 12 Bits 0.5 °C/LSB 0.0625 ±1 0°C = TA ≤ +50°C, VS = +3.0V to +3.6V ±1.5 0°C = TA ≤ +70°C, VS = +3.0V to +3.6V ±2.0 VS = +3V to +5.5V Conversion Time tC OT Pullup Resistor RP MAX6625R, MAX6626R only OT Saturation Voltage (Note 4) VL IOUT = 4mA OT Delay V Shutdown mode MAX6626 TA = +25°C, VS = +3V to +3.6V Accuracy (Notes 2, 3) UNITS 5.5 250 MAX6625 Temperature Resolution MAX °C/V 1 133 (Programmable through fault queue) °C ms 25 50 kΩ 0.8 V 1 × tC 6 × tC ms THIGH Default Temperature THIGH 80 °C TLOW Default Temperature TLOW 75 °C I2C-COMPATIBLE I/O: SCL, SDA, ADD Input High Voltage VIH Input Low Voltage VIL Input Hysteresis 2 VS < +3.6V 2 VS > +3.6V 3 V 0.8 0.2 _______________________________________________________________________________________ V V 9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 (+3V ≤ VS ≤ +5.5V, TA = -55°C to +125°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Input High Leakage Current IIH VIN = +5V ±1 µA Input Low Leakage Current IIL VIN = 0 ±1 µA Input Capacitance CIN Output Low Voltage VOL IOL = 3mA 0.4 V Output High Current IOH VOH = 5V 1 µA 400 kHz 10 pF I2C-COMPATIBLE TIMING Serial Clock Frequency fSCL DC Bus Free Time Between STOP and START Conditions tBUF 1.3 µs START Condition Hold Time tHD:STA 0.6 µs STOP Condition Setup Time tSU:STO 0.6 µs Clock Low Period tLOW 1.3 µs Clock High Period tHIGH 0.6 µs Data Setup Time tSU:DAT 100 Data Hold Time (Note 5) tHD:DAT 0 ns 0.9 µs Maximum Receive SCL/SDA Rise Time (Note 6) tR 300 ns Minimum Receive SCL/SDA Rise Time (Note 6) tR 20 + 0.1CB ns Maximum Receive SCL/SDA Fall Time (Note 6) tF 300 ns Minimum Receive SCL/SDA Fall Time (Note 6) tF 20 + 0.1CB ns Transmit SDA Fall Time (Note 6) tF Pulse Width of Suppressed Spike (Note 7) 20 + 0.1CB CB = 400pF, IO = 3mA tSP 250 50 ns ns 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 tR tLOW tHIGH tHD:STA tSU:DAT tHD:DAT tSU:STO SDA tBUF Figure 1. Serial Bus Timing _______________________________________________________________________________________ 3 MAX6625/MAX6626 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VS = +3.3V, TA = +25°C, unless otherwise noted.) STATIC QUIESCENT SUPPLY CURRENT vs. TEMPERATURE RESPONSE TO THERMAL SHOCK TEMPERATURE vs. TIME 60 40 MAX6625 toc02 180 INPUT CURRENT (µA) 80 20 160 140 120 100 DEVICE IMMERSED IN +85°C FLUORINERT BATH 80 0 -5 0 5 10 15 -55 20 -25 5 35 65 95 TIME (s) TEMPERATURE (°C) DYNAMIC QUIESCENT SUPPLY CURRENT vs. TEMPERATURE TEMPERATURE ERROR vs. TEMPERATURE 5 MAX6625 toc03 200 4 TEMPERATURE ERROR (°C) 180 160 140 120 125 MAX6625 toc04 OUTPUT TEMPERATURE (°C) 200 MAX6625 toc01 100 INPUT CURRENT (µA) MAX6625/MAX6626 9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 MAXIMUM LIMIT 3 2 1 ±5 SIGMA RANGE 0 -1 -2 -3 100 MINIMUM LIMIT -4 80 -5 -55 -25 5 35 65 95 125 -50 TEMPERATURE (°C) -25 0 25 50 75 100 125 TEMPERATURE (°C) Pin Description PIN 4 NAME FUNCTION I2C-Compatible Serial Bidirectional Data Line 1 SDA 2 GND Power-Supply Ground 3 SCL I2C-Compatible Clock Input 4 OT Temperature Alarm Output 5 ADD 6 VS 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 0.1µF capacitor. _______________________________________________________________________________________ 9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 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- BANDGAP REGISTER 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. REFERENCE ADC TEMP SIGNAL MAX6625 MAX6626 +Vs TEMPERATURE REGISTER ADDRESS POINTER REGISTER THIGH REGISTER MAX665_ R ONLY SET-POINT COMPARATOR OT TLOW REGISTER CONFIGURATION REGISTER SERIAL BUS INTERFACE FAULT QUEUE COUNTER GND SDA SCL ADD Figure 2. Functional Block Diagram _______________________________________________________________________________________ 5 MAX6625/MAX6626 Detailed Description 6 START BY MASTER START BY MASTER START BY MASTER ADDRESS BYTE ADDRESS BYTE ADDRESS BYTE POINTER BYTE ACK BY REPEAT MAX6625 START BY MASTER ADDRESS BYTE ACK BY MAX6625 ACK BY MAX6625 ACK BY MAX6625 POINTER BYTE POINTER BYTE CONFIGURATION BYTE MOST-SIGNIFICANT DATA BYTE (c) THIGH AND TLOW WRITE ACK BY MAX6625 (b) CONFIGURATION REGISTER WRITE ACK BY MAX6625 ACK BY MAX6625 MAX6625 DATA BYTE LEAST-SIGNIFICANT DATA BYTE STOP COND BY ACK BY MASTER (a) TYPICAL POINTER SET FOLLOWED BY IMMEDIATE READ FROM CONFIGURATION REGISTER ACK BY MAX6625 ACK BY MAX6625 STOP COND BY MASTER NO ACK BY MASTER STOP COND BY MASTER MAX6625/MAX6626 9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 Figure 3. I2C-Compatible Timing Diagram _______________________________________________________________________________________ _______________________________________________________________________________________ START BY MASTER START BY MASTER START BY MASTER REPEAT START BY MASTER ADDRESS BYTE ADDRESS BYTE ADDRESS BYTE ACK BY MASTER ACK BY MASTER LEAST-SIGNIFICANT DATA BYTE ACK BY MAX6625 POINTER BYTE MOST-SIGNIFICANT DATA BYTE ACK BY MAX6625 ACK BY MASTER DATA BYTE NO ACK BY MASTER (c) TYPICAL 1-BYTE READ FROM CONFIGURATION REGISTER WITH PRESET POINTER ACK BY MAX6625 STOP COND BY MASTER (b) TYPICAL POINTER SET FOLLOWED BY IMMEDIATE READ FOR 2-BYTE REGISTER SUCH AS TEMP, THIGH, TLOW ADDRESS BYTE MOST-SIGNIFICANT DATA BYTE (a) TYPICAL 2-BYTE READ FROM PRESET POINTER LOCATION SUCH AS TEMP, THIGH, TLOW ACK BY MAX6625 LEAST-SIGNIFICANT DATA BYTE NO ACK BY MASTER NO ACK BY MASTER STOP COND BY MASTER MAX6625/MAX6626 STOP COND BY MASTER 9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 Figure 4. I2C-Compatible Timing Diagram 7 MAX6625/MAX6626 9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 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 I2C-COMPATIBLE ADDRESS GND 100 1000 VS 100 1001 Temperature Conversion SDA 100 1010 SCL 100 1011 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 0.5°C for the MAX6625, and 0.0625°C 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 0.5°C for the MAX6625 and 0.0625°C 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 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. 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 _______________________________________________________________________________________ 9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 MAX6625/MAX6626 Table 2. Pointer Register D7 D6 D5 D4 D3 D2 0 0 0 0 0 0 D1 D0 Register select (see Table 3) D7 to D2: Will read all zeros, cannot be written. Table 3. Register Select D1 D0 REGISTER 0 0 0 1 Configuration 1 0 TLOW 1 1 THIGH Temperature (Default) Table 4. Temperature Register PART D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2–D0 MAX6625 MSB (Sign) Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 LSB 0 0 0 0 0 MAX6625 MSB (Sign) Bit 11 Bit 10 Bit 9 Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 LSB 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. Table 5. Configuration Register D7 0 D6 0 D5 0 D4 D3 Fault Queue Depth D2 OT Polarity D1 Comparator or Interrupt Mode 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. 1LSB = 0.5°C for the MAX6625. 1LSB = 0.0.0625°C for the MAX6626. Temperature is stored in two’s-complement format. Table 6. Fault Queue Depth D0 Shutdown D4 D3 NUMBER OF FAULTS 0 0 1 (Default) 0 1 2 1 0 4 1 1 6 _______________________________________________________________________________________ 9 MAX6625/MAX6626 9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 Table 7. THIGH and TLOW Registers D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 MSB Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 LSB 0 0 0 0 0 0 0 D6 to D0: Will read all zeros, cannot be written. D15: MSB is the sign bit. Default: THIGH = +80°C (5000H), TLOW = +75°C (4B00H). LSB = 0.5°C. Table 8. Output Code vs. Temperature DIGITAL OUTPUT CODE MAX6625 TEMPERATURE (°C) BINARY MSB LSB MAX6626 HEX BINARY MSB LSB +125.0000 0111 1101 0000 0000 7D00 0111 1101 0000 0000 7D00 +124.9375 0111 1100 1000 0000 7C80 0111 1100 1111 0000 7CF0 +25.0000 0001 1001 0000 0000 1900 0001 1001 0000 0000 1900 +0.5000 0000 0000 1000 0000 0080 0000 0000 1000 0000 0080 0.0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 -0.5000 1111 1111 1000 0000 FF80 1111 1111 1000 0000 FF80 -25.0000 1110 0111 0000 0000 E700 1110 0111 0000 0000 E700 -55.0000 1100 1001 0000 0000 C900 1100 1001 0000 0000 C900 ∗ 1000 0000 0000 0000 8000 1000 0000 0000 0000 8000 *8000H is the default value at power-up and after coming out of shutdown. 10 HEX ______________________________________________________________________________________ 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 35kΩ (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 +100°C, TLOW is set to +80°C, and the fault queue depth is set to four, OT will not assert until four consecutive conversions exceed +100°C. Then, OT will not deassert until four consecutive conversions are less than +80°C. 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. ______________________________________________________________________________________ 11 MAX6625/MAX6626 9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 Example 1: If THIGH is set to +100°C, TLOW is set to +80°C, and the fault queue depth is set to four, OT will not assert until four consecutive conversions exceed +100°C. 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 +80°C. Example 2: If THIGH is set to +100°C, TLOW is set to +80°C, and the fault queue depth is set to four, OT will not assert until four consecutive conversions exceed +100°C. If the T HIGH register is then changed to +120°C, 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 µP, allowing the device to monitor the µP’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 ✕ θJA 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 1µA (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. where PD is the power dissipated by the MAX6625/ MAX6626, and θJA is the package’s thermal resistance. The typical thermal resistance is +110°C/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 0.35°C rise in the die temperature. 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 12V 300mA FAN MOTOR 6 4 OT MAX6625R MAX6626R 6 LOGIC LEVEL MOSFET 4k RELAY 5VDC, 20mA 125VAC, 1A MAX6625P MAX6626P OT 5 2N3904 2 HEATER SUPPLY 3 Figure 7. Fan Controller 12 Figure 8. Simple Thermostat ______________________________________________________________________________________ 9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23 ALARM OUTPUT RESOLUTION (bits) TOP MARK MAX6625PMUT Open Drain 9 AAHY MAX6625RMUT Internal Pullup 9 AAHZ MAX6626PMUT Open Drain 12 AANP MAX6626RMUT Internal Pullup 12 AANQ PART Chip Information TRANSISTOR COUNT: 7513 PROCESS: BiCMOS Package Information 6LSOT.EPS (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.) 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 © 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX6625/MAX6626 Selector Guide