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19-1485; Rev 0; 4/99
SOT Temperature Sensor with Multidrop Single-Wire Digital Interface
General Description
The MAX6575L/H is a low-cost, low-current temperature sensor with a single-wire digital interface. It features accuracy of 3C at +25C, 4.5C at +85C, and 5C at +125C. The MAX6575L/H is a monostable, externally triggered temperature sensor that allows a microprocessor (P) 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
o Simple Single-Wire Interface to P or C o Multidrop up to Eight Sensors on One Wire o 0.8C Accuracy at +25C (3C max) o Operates from +2.7V to +5.5V Supply Voltage o Low 150A (typ) Supply Current o Standard Operating Temperature Range: -40C to +125C o Small 6-Pin SOT23 Package
MAX6575L/H
Ordering Information
PART MAX6575LZUT MAX6575HZUT TEMP. RANGE -40C to +125C -40C to +125C SOT PINPACKAGE TOP MARK 6 SOT23 6 SOT23 AABG AABH
Applications
Critical P and C Temperature Monitoring Portable Battery-Powered Equipment Cell Phones Battery Packs Hard Drives/Tape Drives Networking and Telecom Equipment Medical Equipment Automotive
PART MAX6575L MAX6575H
Selector Guide
TIMEOUT MULTIPLIERS (s/K) 5, 20, 40, 80 160, 320, 480, 640
Pin Configurations appear at end of data sheet.
Typical Operating Circuit
+2.7V TO +5.5V VCC 0.1F 0.1F VDD 0.1F VDD
MAX6575L
VCC TS1 10k TS0 I/O
MAX6575H
TS1 GND TS0 I/O
CHIP #1
CHIP #8
GND
P
I/O GND
________________________________________________________________ Maxim Integrated Products
1
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SOT Temperature Sensor with Multidrop Single-Wire Digital Interface MAX6575L/H
ABSOLUTE MAXIMUM RATINGS
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 Continuous Power Dissipation (TA = +70C) 6-Pin SOT23 (derate 7.10mW/C above +70C)...........571mW Operating Temperature Range .........................-40C to +125C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10sec) .............................+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
(VDD = +2.7V to +5.5V, TA = -40C to +125C, unless otherwise noted. Typical values are specified at TA = +25C and VDD = +5V, unless otherwise noted.) PARAMETER VDD Range Supply Current SYMBOL VDD IDD VDD = 5.5V TA = -20C Temperature Sensor Error (Note 1) TA = 0C TA = +25C TA = +85C TA = +125C tD1 tD2 tD3 Output Pulse Delay tD4 tD5 tD6 tD7 tD8 Output Pulse Low Time Reset Pulse Width (Note 2) Setup Time Start Pulse (Note 3) Delay Time from Trigger to Ready (Note 4) Glitch Immunity on I/O Input Time-Select Pin Logic Levels I/O Output Voltage Low I/O Input Voltage Low I/O Input Voltage High Note 1: Note 2: Note 3: Note 4: 2 VIL VIH VOL VIL VIH 2.3 VDD > 4.5V, ISINK = 3.2mA VDD > 2.7V, ISINK = 1.2mA 2.3 0.4 0.3 0.8 tL1-8 tRESET tSETUP tSTART tREADY Figure 1 Figure 1 Figure 1 Figure 1, TA = +25C Figure 1 500 0.8 2.5 520 4.6 10 MAX6575H, T (temp) in K, Figure 1 MAX6575L, T (temp) in K, Figure 1 VTS1 = GND, VTS0 = GND VTS1 = GND, VTS0 = VDD VTS1 = VDD, VTS0 = GND VTS1 = VDD, VTS0 = VDD VTS1 = GND, VTS0 = GND VTS1 = GND, VTS0 = VDD VTS1 = VDD, VTS0 = GND VTS1 = VDD, VTS0 = VDD TA = -40C to +85C TA = -40C to +125C -7.5 -5.5 -3.0 -4.5 -5.0 1.1 0.9 0.8 0.5 0.5 5T 20T 40T 80T 160T 320T 480T 640T 5T 16.0 s ms s s ms ns V V V V s CONDITIONS MIN 2.7 150 TYP MAX 5.5 250 400 +7.5 +5.5 +3.0 +4.5 +5.0 C UNITS V A
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.
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SOT Temperature Sensor with Multidrop Single-Wire Digital Interface
Typical Operating Characteristics
(VDD = +5V, TA = +25C, unless otherwise noted.)
TEMPERATURE ACCURACY (TA = +25C)
MAX6575 toc01
MAX6575L/H
TEMPERATURE ACCURACY (TA = +85C)
SAMPLE SIZE = 200 PERCENTAGE OF PARTS SAMPLED (%) 35 30 25 20 15 10 5 0 -1.0 -5 -4 -3 -2 -1 0 1 2 3 4 5 ACCURACY (C) 0.5
MAX6575 toc02
ACCURACY vs. TEMPERATURE
MAX6576 toc3a
35 PERCENTAGE OF PARTS SAMPLED (%) 30 25 20 15 10 5 0
SAMPLE SIZE = 200
40
1.5
1.0
0
-0.5
-5 -4
-3 -2 -1
0
1
2
3
4
5
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
ACCURACY (C)
ACCURACY (C)
SUPPLY CURRENT vs. TEMPERATURE
MAX6575L/H-03
THERMAL STEP RESPONSE IN PERFLUORINATED FLUID
MAX6575L/H-04
THERMAL STEP RESPONSE IN STILL AIR
MAX6575L/H-05
190 180 SUPPLY CURRENT (A) 170 160 150 140 130 120
+100C +100C
+15C/div MOUNTED ON 0.75 in.2 OF 2oz. COPPER +25C -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) 5sec/div
+12.5C/div
MOUNTED ON 0.75 in.2 OF 2oz. COPPER +25C 20sec/div
Pin Description
PIN 1 2 3 4, 5 6 NAME VDD GND N.C. TS0, TS1 I/O Positive Supply Voltage Ground No Connect. Connect pin to GND or leave open. Time-Select Pins. Set the time delay factor by connecting TS1 and TS0 to either VDD or GND. See Table 1. 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). FUNCTION
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SOT Temperature Sensor with Multidrop Single-Wire Digital Interface MAX6575L/H
_______________Detailed Description
The MAX6575L/H low-cost, low-current (150A typ) temperature sensor is ideal for interfacing with microcontrollers or microprocessors. The MAX6575L/H is a monostable, externally triggered temperature sensor that uses a TempDelay conversion to communicate with a P 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.
Table 1. Time-Select Pin Configuration
TIME-SELECT PINS TS1 GND GND VDD VDD TS0 GND VDD GND VDD TIMEOUT MULTIPLIERS (s/K) MAX6575L 5 20 40 80 MAX6575H 160 320 480 640
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. tDx: Timing delay between the falling edge of the start pulse and the falling edge initiated by CHIP#x. I/O pulse low time (5Ts).
Operating the MAX6575L/H
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 5Ts, 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-
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(s) / timeout multiplier(s/K)] - 273.15K
tSETUP
APPLIED START PULSE
CHIP# 1 RESPONSE
CHIP# 2 RESPONSE
CHIP# 3 RESPONSE
CHIP# 4 RESPONSE
tSTART tRESET tD1
tL1 tD2 tD3
tL2
tL3
tL4
tD4 tREADY
Figure 1. Timing Diagram
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SOT Temperature Sensor with Multidrop Single-Wire Digital Interface MAX6575L/H
Table 2. Allowable Temperature Differential (C)
TIMEOUT MULTIPLIER 5 20 40 80 160 320 480 640 MAX6575L 5 20 >165 40 >165 95.5 80 >165 >165 132.0 160 >165 >165 >165 153.5 MAX6575H 320 >165 >165 >165 >165 >165 480 >165 >165 >165 >165 >165 70.2 640 >165 >165 >165 >165 >165 >165 37.9
Table 3. Typical Peak Noise Amplitude
PARAMETER Timeout Multiplier Noise Amplitude (C) 5 20 MAX6575L 40 80 160 MAX6575H 320 480 640
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).
For example, if the maximum temperature differential in a system is 80C, the only combinations of timeout multipliers that could result in timeout overlap would be a 320:480s/K (70.2C) or a 480:640s/K (37.9C) 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 80C. A similar analysis shows that four MAX6575L/H parts can be used when the maximum temperature differential extends over the entire 165C range of the part.
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 165C indicate no overlap.
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 0.1F 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.
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SOT Temperature Sensor with Multidrop Single-Wire Digital Interface MAX6575L/H
+2.7V TO +5.5V +2.7V TO +5.5V
VDD
0.1F
VDD
0.1F
40s/K
TS1 TS0
MAX6575L
I/O T1
80s/K
TS1 TS0
MAX6575L
I/O T2
GND
GND VCC 470 (8) 10k P3.7 P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 10k OPEN: T1 CLOSED: T2 P3.5 X1 12MHz GND X2 22pF P1.6 P1.7 22pF
8051
VCC
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 40s/K, while the second device, T2, is configured for a timeout multiplier of 80s/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
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SOT Temperature Sensor with Multidrop Single-Wire Digital Interface MAX6575L/H
Listing 1. 8051 Code Example
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SOT Temperature Sensor with Multidrop Single-Wire Digital Interface MAX6575L/H
Listing 1. 8051 Code Example (continued)
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SOT Temperature Sensor with Multidrop Single-Wire Digital Interface MAX6575L/H
Listing 1. 8051 Code Example (continued)
Pin Configuration
TRANSISTOR COUNT: 302
TOP VIEW
VDD 1 6 I/O
Chip Information
GND 2
MAX6575L MAX6575H
5
TS1
N.C. 3
4
TS0
SOT23-6
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SOT Temperature Sensor with Multidrop Single-Wire Digital Interface MAX6575L/H
Package Information
6LSOT.EPS
10
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SOT Temperature Sensor with Multidrop Single-Wire Digital Interface
NOTES
MAX6575L/H
11
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SOT Temperature Sensor with Multidrop Single-Wire Digital Interface MAX6575L/H
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 (c) 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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