19-1485; Rev 0; 4/99 SOT Temperature Sensor with Multidrop Single-Wire Digital Interface The MAX6575L/H is a low-cost, low-current temperature sensor with a single-wire digital interface. It features accuracy of ±3°C at +25°C, ±4.5°C at +85°C, and ±5°C at +125°C. The MAX6575L/H is a monostable, externally triggered temperature sensor that allows a microprocessor (µP) to interface with up to eight temperature sensors using a single control line. Temperatures are sensed by measuring the time delay between the falling edge of the external triggering pulse and the falling edge of the subsequent pulse delays reported from the devices. Different sensors on the same I/O line use different timeout multipliers to avoid overlapping signals. The MAX6575L/H features eight different timeout multipliers; these are selectable by using the two time-select pins on each device and choosing the “L” or “H” version. The “L” version provides four delay ranges less than 50ms. The “H” version provides four delay ranges greater than 50ms. The MAX6575L/H is available in a space-saving 6-pin SOT23 package. Features ♦ Simple Single-Wire Interface to µP or µC ♦ Multidrop up to Eight Sensors on One Wire ♦ ±0.8°C Accuracy at +25°C (±3°C max) ♦ Operates from +2.7V to +5.5V Supply Voltage ♦ Low 150µA (typ) Supply Current ♦ Standard Operating Temperature Range: -40°C to +125°C ♦ Small 6-Pin SOT23 Package Ordering Information TEMP. RANGE SOT PINPACKAGE TOP MARK MAX6575LZUT -40°C to +125°C 6 SOT23 AABG MAX6575HZUT -40°C to +125°C 6 SOT23 AABH PART Applications Selector Guide Critical µP and µC Temperature Monitoring Portable Battery-Powered Equipment Cell Phones Battery Packs Hard Drives/Tape Drives Networking and Telecom Equipment Medical Equipment Automotive PART TIMEOUT MULTIPLIERS (µs/°K) MAX6575L 5, 20, 40, 80 MAX6575H 160, 320, 480, 640 Pin Configurations appear at end of data sheet. Typical Operating Circuit +2.7V TO +5.5V VCC 0.1µF 0.1µF VDD VDD 0.1µF MAX6575L TS1 VCC 10k MAX6575H TS1 CHIP #1 TS0 GND I/O CHIP #8 TS0 GND I/O µP I/O GND ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. MAX6575L/H General Description MAX6575L/H SOT Temperature Sensor with Multidrop Single-Wire Digital Interface ABSOLUTE MAXIMUM RATINGS Continuous Power Dissipation (TA = +70°C) 6-Pin SOT23 (derate 7.10mW/°C above +70°C)...........571mW Operating Temperature Range .........................-40°C to +125°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10sec) .............................+300°C Terminal Voltage (with respect to GND) VDD ........................................................................-0.3V to +6V TS1, TS0 ..................................................-0.3V to (VDD + 0.3V) I/O..........................................................................-0.3V to +6V Input/Output Current, All Pins...........................................±20mA 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 (VDD = +2.7V to +5.5V, TA = -40°C to +125°C, unless otherwise noted. Typical values are specified at TA = +25°C and VDD = +5V, unless otherwise noted.) PARAMETER VDD Range Supply Current SYMBOL CONDITIONS VDD IDD Temperature Sensor Error (Note 1) tD3 Output Pulse Delay VDD = 5.5V TA = -40°C to +85°C V 250 TA = -40°C to +125°C 400 -7.5 ±1.1 +7.5 TA = 0°C -5.5 ±0.9 +5.5 TA = +25°C -3.0 ±0.8 +3.0 TA = +85°C -4.5 ±0.5 +4.5 TA = +125°C -5.0 ±0.5 +5.0 MAX6575L, T (temp) in °K, Figure 1 VTS1 = GND, VTS0 = GND 5T VTS1 = GND, VTS0 = VDD 20T VTS1 = VDD, VTS0 = GND 40T 80T tD5 VTS1 = GND, VTS0 = GND 160T VTS1 = GND, VTS0 = VDD 320T VTS1 = VDD, VTS0 = GND 480T VTS1 = VDD, VTS0 = VDD 640T MAX6575H, T (temp) in °K, Figure 1 tL1-8 Figure 1 Reset Pulse Width (Note 2) tRESET Figure 1 Setup Time tSETUP Figure 1 Start Pulse (Note 3) tSTART Figure 1, TA = +25°C Delay Time from Trigger to Ready (Note 4) tREADY Figure 1 10 VOL I/O Input Voltage Low VIL I/O Input Voltage High VIH ms µs 2.5 µs 520 500 I/O Output Voltage Low °C µs 16.0 VIL 2.3 VDD > 4.5V, ISINK = 3.2mA 0.4 VDD > 2.7V, ISINK = 1.2mA 0.3 0.8 2.3 See Temperature Accuracy histograms in Typical Operating Characteristics. Guaranteed by design. Not production tested. Limit maximum start pulse at 1ms to avoid timing overlap. If no reset pulse is applied. _______________________________________________________________________________________ ms ns 0.8 VIH µA µs 5T 4.6 Glitch Immunity on I/O Input 2 5.5 150 TA = -20°C tD8 Note 1: Note 2: Note 3: Note 4: UNITS VTS1 = VDD, VTS0 = VDD tD7 Time-Select Pin Logic Levels MAX tD4 tD6 Output Pulse Low Time TYP 2.7 tD1 tD2 MIN V V V V SOT Temperature Sensor with Multidrop Single-Wire Digital Interface TEMPERATURE ACCURACY (TA = +85°C) 20 15 10 5 -5 -4 -3 -2 -1 0 1 2 3 4 MAX6576 toc3a 1.0 30 25 20 15 10 0.5 0 -0.5 5 -1.0 0 0 -5 -4 5 -3 -2 -1 0 1 2 3 4 -40 -25 -10 5 20 35 50 65 80 95 110 125 5 ACCURACY (°C) ACCURACY (°C) TEMPERATURE (°C) SUPPLY CURRENT vs. TEMPERATURE THERMAL STEP RESPONSE IN PERFLUORINATED FLUID THERMAL STEP RESPONSE IN STILL AIR MAX6575L/H-05 MAX6575L/H-04 MAX6575L/H-03 190 180 SUPPLY CURRENT (µA) SAMPLE SIZE = 200 35 ACCURACY (°C) 25 ACCURACY vs. TEMPERATURE 1.5 MAX6575 toc02 SAMPLE SIZE = 200 30 40 PERCENTAGE OF PARTS SAMPLED (%) PERCENTAGE OF PARTS SAMPLED (%) 35 MAX6575 toc01 TEMPERATURE ACCURACY (TA = +25°C) MAX6575L/H Typical Operating Characteristics (VDD = +5V, TA = +25°C, unless otherwise noted.) +100°C +100°C 170 160 +12.5°C/div +15°C/div 150 140 MOUNTED ON 0.75 in.2 OF 2oz. COPPER 130 MOUNTED ON 0.75 in.2 OF 2oz. COPPER +25°C +25°C 120 -40 -25 -10 5 20 35 50 65 80 95 110 125 20sec/div 5sec/div TEMPERATURE (°C) Pin Description PIN NAME FUNCTION 1 VDD Positive Supply Voltage 2 GND Ground No Connect. Connect pin to GND or leave open. 3 N.C. 4, 5 TS0, TS1 Time-Select Pins. Set the time delay factor by connecting TS1 and TS0 to either VDD or GND. See Table 1. 6 I/O Bidirectional Interface Pin. A time delay between when the part is initiated externally by pulling I/O low and when the part subsequently pulls I/O low, is proportional to absolute temperature (°K). _______________________________________________________________________________________ 3 MAX6575L/H SOT Temperature Sensor with Multidrop Single-Wire Digital Interface _______________Detailed Description Table 1. Time-Select Pin Configuration The MAX6575L/H low-cost, low-current (150µA typ) temperature sensor is ideal for interfacing with microcontrollers or microprocessors. The MAX6575L/H is a monostable, externally triggered temperature sensor that uses a Temp→Delay conversion to communicate with a µP over a single I/O line. Time-select pins (TS1, TS0) permit the internal temperature-controlled oscillator (TCO) to be scaled by four preset timeout multipliers, allowing eight separate temperature sensors to share one I/O line. Different sensors on the same I/O line will use different timeout multipliers to avoid overlapping signals. Operating the MAX6575L/H APPLIED START PULSE tSTART tRESET CHIP# 1 RESPONSE tL1 tD1 TS1 TS0 MAX6575L MAX6575H GND GND 5 160 GND VDD 20 320 VDD GND 40 480 VDD VDD 80 640 mum delay of 520ms, at which point it will again be in a ready state awaiting a start pulse. Definition of Terms: tRESET: Time I/O must be externally pulled low to guarantee the MAX6575L/H is in a ready state awaiting external trigger. (Part will assume a ready state after 520ms without a reset pulse.) tSETUP: Time I/O must be high prior to a start pulse. tSTART: Trigger pulse which starts the on-chip timing sequence on its falling edge. Figure 1 illustrates the timing for the MAX6575L/H. When the device is powered up, it assumes a ready state where it awaits an external trigger at the I/O pin. The I/O pin of the MAX6575L/H has an open-drain output structure that requires a pull-up resistor to maintain the proper logic levels. Once the I/O pin is pulled low and then released, control of the I/O pin is transferred to the MAX6575L/H. The temperature conversion begins on the falling edge of the externally triggered pulse. The I/O line is pulled low at a later time. That time is determined by the device temperature and the Time Select pins (TS1, TS0). The I/O line remains low for 5Tµs, where T is the temperature in degrees Kelvin. The temperature of the device is represented by the edgeto-edge delay of the externally triggered pulse and the falling edge of the subsequent pulse originating from the device. The device can be manually reset by pulling the I/O line low for more than tRESET (16ms max). The device will automatically reset after a maxi- tSETUP TIMEOUT MULTIPLIERS (µs/°K) TIME-SELECT PINS tDx: Timing delay between the falling edge of the start pulse and the falling edge initiated by CHIP#x. I/O pulse low time (5Tµs). tLx: tREADY: Time after falling edge of start pulse when the MAX6575L/H will reset itself and await the next external trigger. The temperature, in degrees Celsius, may be calculated as follows: T(°C) = [tDx(µs) / timeout multiplier(µs/°K)] - 273.15°K CHIP# 2 RESPONSE CHIP# 3 RESPONSE tL3 tL2 CHIP# 4 RESPONSE tL4 tD2 tD3 tD4 tREADY Figure 1. Timing Diagram 4 _______________________________________________________________________________________ SOT Temperature Sensor with Multidrop Single-Wire Digital Interface MAX6575L/H Table 2. Allowable Temperature Differential (°C) TIMEOUT MULTIPLIER MAX6575L 5 5 MAX6575H 20 40 80 160 320 480 640 >165 >165 >165 >165 >165 >165 >165 95.5 >165 >165 >165 >165 >165 132.0 >165 >165 >165 >165 153.5 >165 >165 >165 >165 >165 >165 70.2 >165 20 40 80 160 320 480 37.9 640 Table 3. Typical Peak Noise Amplitude PARAMETER MAX6575L MAX6575H Timeout Multiplier 5 20 40 80 160 320 480 640 Noise Amplitude (°C) ±0.33 ±0.15 ±0.15 ±0.098 ±0.091 ±0.063 ±0.043 ±0.037 Time-Select Pins (TS1, TS0) Table 1 shows the configuration of the Time-select pins for the MAX6575L/H. Each device allows four selectable timeout multipliers intended to prevent overlapping when multiple devices are used on the same I/O line. Tie TS1 and TS0 to either GND or VDD to select the desired temperature multiplier. To monitor several chips on the same I/O line, different timeout multipliers should be selected using the TS1 and TS0 pins. The timeout periods are then scaled so that the response times will not overlap (see Timeout Selection). Applications Information Timeout Selection Under extreme temperature conditions, it is possible for an overlap to occur between the timeout delays of different sensors in a multidrop configuration. This overlap can occur only if the temperature differential recorded between two devices is very large. Timeout overlaps can be avoided in multidrop configurations by selecting the appropriate timeout multipliers. Table 2 illustrates the allowable temperature differential between devices when the maximum error is present on each device. Allowable temperature differentials greater than 165°C indicate no overlap. For example, if the maximum temperature differential in a system is 80°C, the only combinations of timeout multipliers that could result in timeout overlap would be a 320:480µs/°K (70.2°C) or a 480:640µs/°K (37.9°C) combination. As long as these combinations of timeout multipliers are not used in the same multidrop configuration, no overlap can occur. Thus, seven MAX6575L/H parts can be used in the same multidrop configuration if the maximum temperature differential between parts is 80°C. A similar analysis shows that four MAX6575L/H parts can be used when the maximum temperature differential extends over the entire 165°C range of the part. Noise Considerations The accuracy of the MAX6575L/H timeout delay is susceptible to noise generated both internally and externally. The effects of external noise can be minimized by placing a 0.1µF ceramic bypass capacitor close to the device’s supply pin. Internal noise is inherent in the operation of the device and is detailed in Table 3. Internal averaging minimizes the effect of this noise when using longer timeout multipliers. The effects of this noise are included in the overall accuracy of the device as specified in the Electrical Characteristics table. _______________________________________________________________________________________ 5 MAX6575L/H SOT Temperature Sensor with Multidrop Single-Wire Digital Interface +2.7V TO +5.5V +2.7V TO +5.5V 0.1µF VDD 40µs/°K TS1 MAX6575L I/O T1 TS0 0.1µF VDD 80µs/°K TS1 MAX6575L I/O T2 TS0 GND GND VCC 470Ω (8) P1.0 10k P1.1 P3.7 8051 VCC P1.2 P1.3 P1.4 P1.5 P1.6 10k OPEN: T1 CLOSED: T2 P1.7 P3.5 22pF X1 12MHz GND X2 22pF Figure 2. Interfacing Multiple Devices with a Microcontroller Interfacing Multiple Devices with a Microcontroller Figure 2 shows how to interface multiple MAX6575L/H devices with an 8051 microcontroller. The first device, T1, is configured for a timeout multiplier of 40µs/°K, while the second device, T2, is configured for a timeout multiplier of 80µs/°K to avoid overlap. The microcontroller takes in temperature values from both sensors, T1 and T2, on a single port pin, P3.7. The microcontroller displays five times the temperature in degrees Celsius in binary on Port 1. A switch connected to a pull-up resistor at Port 3.5 selects which temperature is displayed: open = T1, closed = T2. Code is provided for this application as Listing 1. 6 _______________________________________________________________________________________ SOT Temperature Sensor with Multidrop Single-Wire Digital Interface MAX6575L/H Listing 1. 8051 Code Example _______________________________________________________________________________________ 7 MAX6575L/H SOT Temperature Sensor with Multidrop Single-Wire Digital Interface Listing 1. 8051 Code Example (continued) 8 _______________________________________________________________________________________ SOT Temperature Sensor with Multidrop Single-Wire Digital Interface MAX6575L/H Listing 1. 8051 Code Example (continued) Pin Configuration Chip Information TRANSISTOR COUNT: 302 TOP VIEW VDD 1 GND 2 MAX6575L MAX6575H N.C. 3 6 I/O 5 TS1 4 TS0 SOT23-6 _______________________________________________________________________________________ 9 SOT Temperature Sensor with Multidrop Single-Wire Digital Interface 6LSOT.EPS MAX6575L/H Package Information 10 ______________________________________________________________________________________ SOT Temperature Sensor with Multidrop Single-Wire Digital Interface ______________________________________________________________________________________ MAX6575L/H NOTES 11 MAX6575L/H SOT Temperature Sensor with Multidrop Single-Wire Digital Interface NOTES 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 © 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.