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19-1484; Rev 0; 4/99
SOT Temperature Sensors with Period/Frequency Output
General Description
The MAX6576/MAX6577 are low-cost, low-current temperature sensors with a single-wire output. The MAX6576 converts the ambient temperature into a square wave with a period proportional to absolute temperature (K). The MAX6577 converts the ambient temperature into a square wave with a frequency proportional to absolute temperature. The MAX6576 offers accuracy of 3C at +25C, 4.5C at +85C, and 5C at +125C. The MAX6577 offers accuracy of 3C at +25C, 3.5C at +85C, and 4.5C at +125C. Both devices feature a single-wire output that minimizes the number of pins necessary to interface with a microprocessor. The period/frequency range of the output square wave can be selected by hard-wiring the two time-select pins (TS0, TS1) to either VDD or GND. The MAX6576/MAX6577 are available in space-saving 6-pin SOT23 packages. o Simple Single-Wire Output o Two Output Types Available Temperature to Period (s) (MAX6576) Temperature to Frequency (Hz) (MAX6577) o 0.8C Accuracy at +25C (3C max) o No External Components o Operates from +2.7V to +5.5V Supply Voltage o Low 140A Typical Supply Current o Standard Operating Temperature Range: -40C to +125C o Small 6-Pin SOT23 Package
Features
MAX6576/MAX6577
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
MAX6576ZUT -40C to +125C MAX6577ZUT -40C to +125C PART
Ordering Information
TEMP. RANGE PINPACKAGE 6 SOT23 6 SOT23 SOT TOP MARK
AABI AABJ
Pin Configuration
TOP VIEW
+2.7V TO +5.5V 0.1F VDD 1 6 OUT
Typical Operating Circuit
VDD
0.1F
VCC
GND 2
MAX6576 MAX6577
MAX6576
5 TS1 TS1 MAX6577 TS0 GND OUT
P
GND I/O
N.C. 3
4
TS0
SOT23-6
________________________________________________________________ Maxim Integrated Products
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SOT Temperature Sensors with Period/Frequency Output MAX6576/MAX6577
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND) VDD ......................................................................-0.3V to +6V TS1, TS0, OUT.......................................-0.3V to (VDD + 0.3V) 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 = -40C to +85C TA = -40C to +125C TA = -20C TA = 0C MAX6576 Temperature Sensor Error (Note 1) MAX6577 TA = +25C TA = +85C TA = +125C TA = -20C TA = 0C TA = +25C TA = +85C TA = +125C VTS1 = GND, VTS0 = GND Output Clock Period tOUT MAX6576, T (temp) in K, Figure 1 VTS1 = GND, VTS0 = VDD VTS1 = VDD, VTS0 = GND VTS1 = VDD, VTS0 = VDD VTS1 = GND, VTS0 = GND Output Clock Frequency fOUT MAX6577, T (temp) in K, Figure 2 VTS1 = GND, VTS0 = VDD VTS1 = VDD, VTS0 = GND VTS1 = VDD, VTS0 = VDD OUT Duty Cycle (Note 2) Time-Select Pin Logic Levels VIL VIH VOL OUT Voltage VOH VDD > 4.5V, ISINK = 3.2mA VDD > 2.7V, ISINK = 1.2mA VDD > 4.5V, ISRC = 800A VDD > 2.7V, ISRC = 500A 2.3 0.4 0.3 VDD - 1.5 0.8VDD -7.5 -5.5 -3.0 -4.5 -5.0 -7.5 -6.5 -3.0 -3.5 -4.5 1.1 0.9 0.8 0.5 0.5 1.1 0.9 0.8 0.5 0.5 10T 40T 160T 640T 4T 1T T/4 T/16 0.5 0.8 V Hz s CONDITIONS MIN 2.7 140 TYP MAX 5.5 250 400 +7.5 +5.5 +3.0 +4.5 +5.0 +7.5 +6.5 +3.0 +3.5 +4.5 C C UNITS V A
V
Note 1: See the Temperature Accuracy histograms in the Typical Operating Characteristics. Note 2: The output duty cycle is guaranteed to be 50% by an internal flip-flop. 2 _______________________________________________________________________________________
SOT Temperature Sensors with Period/Frequency Output
Typical Operating Characteristics
(VDD = +5V, TA = +25C, unless otherwise noted.)
TEMPERATURE ACCURACY (TA = +25C)
MAX6576 toc01
MAX6576/MAX6577
TEMPERATURE ACCURACY (TA = +85C)
SAMPLE SIZE = 200 MAX6576 MAX6577 PERCENTAGE OF PARTS SAMPLED (%)
MAX6576 toc01
35 PERCENTAGE OF PARTS SAMPLED (%) 30 25 20 15 10 5 0
60 50 40 30 20 10 0
SAMPLE SIZE = 200 MAX6576 MAX6577
-5 -4 -3 -2 -1
0
1
2
3
4
5
-5 -4 -3 -2 -1
0
1
2
3
4
5
ACCURACY (C)
ACCURACY (C)
SUPPLY CURRENT vs. TEMPERATURE
MAX6576/77toc02
ACCURACY vs. TEMPERATURE
MAX6575 toc04
180 170 SUPPLY CURRENT (A) 160 150 140 130 120 MAX6577 110 100 MAX6576
1.5
1.0 ACCURACY (C)
0.5 MAX6577 0
-0.5 MAX6576
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
-1.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
THERMAL STEP RESPONSE IN PERFLUORINATED FLUID
MAX6576/77 toc05
THERMAL STEP RESPONSE IN STILL AIR
MAX6576/77 toc06
+100C +100C
+12.5C/div +15C/div MOUNTED ON 0.75 in.2 OF 2oz. COPPER +25C 5sec/div 20sec/div MOUNTED ON 0.75 in.2 OF 2oz. COPPER +25C
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SOT Temperature Sensors with Period/Frequency Output MAX6576/MAX6577
Pin Description
PIN 1 2 3 4, 5 6 NAME VDD GND N.C. TS1, TS0 OUT Positive Supply Voltage Ground No Connection. Connect pin to GND or leave open. Time-Select Pins. TS1 and TS0 set the temperature scale factor by connecting TS1 and TS0 to either VDD or GND. See Tables 1 and 2. Square-Wave Output with a Clock Period Proportional to Absolute Temperature (K) (MAX6576) Square-Wave Output with a Clock Frequency Proportional to Absolute Temperature (K) (MAX6577) FUNCTION
Table 1. MAX6576 Time-Select Pin Configuration
TS1 GND GND VDD VDD TS0 GND VDD GND VDD SCALAR MULTIPLIER (s/K) 10 40 160 640
Table 2. MAX6577 Time-Select Pin Configuration
TS1 GND GND VDD VDD TS0 GND VDD GND VDD SCALAR MULTIPLIER (Hz/K) 4 1 1/4 1/16
Note: The temperature, in C, may be calculated as follows:
Note: The temperature, in C, may be calculated as follows:
T(C) =
period(s) scalar mulitplier(s/ K)
- 273.15K
T(C) =
frequency(Hz) scalar mulitplier(Hz/K)
- 273.15K
Detailed Description
The MAX6576/MAX6577 low-cost, low-current (140A typ) temperature sensors are ideal for interfacing with microcontrollers (Cs) or microprocessors (Ps). The MAX6576 converts ambient temperature into a 50% dutycycle square wave with a period proportional to absolute temperature. The MAX6577 converts ambient temperature into a 50% duty-cycle square wave with a frequency proportional to absolute temperature. Time-select pins (TS1, TS0) permit the internal temperature-controlled oscillator (TCO) to be scaled by four preset multipliers. The MAX6576/MAX6577 feature a single-wire interface to minimize the number of port pins necessary for interfacing with a P.
is proportional to the absolute temperature (K) of the device (Figure 1). The MAX6576 has a push/pull CMOS output with sharp edges. The speed of the output square wave can be selected by hard-wiring TS1 and TS0 as shown in Table 1. One of four scaled output periods can be selected using TS1 and TS0.
MAX6577 Characteristics
The MAX6577 temperature sensor converts temperature to frequency. The output of the device is a freerunning, 50% duty-cycle square wave with a frequency that is proportional to the absolute temperature (K) of the device (Figure 2). The MAX6577 has a push/pull CMOS output with sharp edges. The speed of the output square wave can be selected by hard-wiring TS1 and TS0 as shown in Table 2. One of four scaled output frequencies can be selected using TS1 and TS0.
MAX6576 Characteristics
The MAX6576 temperature sensor converts temperature to period. The output of the device is a freerunning, 50% duty-cycle square wave with a period that
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SOT Temperature Sensors with Period/Frequency Output MAX6576/MAX6577
MAX6576 CLOCK WAVEFORM OUTPUT MAX6577 CLOCK WAVEFORM OUTPUT
tOUT
tOUT
fOUT = 1 / tOUT fOUT (K)
Figure 1. MAX6576 Timing Diagram
Figure 2. MAX6577 Timing Diagram
Applications Information
Quick-Look Circuits
Figure 3 shows a quick-look application circuit for the MAX6576 using a universal counter measuring period. TS1 and TS0 are both tied to ground to select a scalar multiplier of 10s/K. The MAX6576 converts the ambient temperature into a square wave with a period that is 10 times the absolute temperature of the device in s. At room temperature, the universal counter will display approximately 2980s. Figure 4 shows a quick-look application circuit for the MAX6577 using a universal counter measuring frequency. TS1 is tied to ground and TS0 is tied to V DD to select a scalar multiplier of 1Hz/K. The MAX6577 converts the ambient temperature into a square wave with a frequency that is equal to the absolute temperature of the device in Hertz. At room temperature, the universal counter will display approximately 298Hz.
tied to VDD to select a scalar multiplier of 1Hz/K. The MAX6577 converts the ambient temperature into a square wave with a frequency that is equal to the absolute temperature of the device in Hertz. The 8051 C reads the frequency of the square-wave output of the MAX6577 into Timer 0 and displays the temperature as degrees Celsius in binary on Port 1. Listing 1 provides the code for this application. The interface is similar for the MAX6576, except the C will perform a period measurement.
Noise Considerations
The accuracy of the MAX6576/MAX6577 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 supply pin of the devices. Internal noise is inherent in the operation of the devices and is detailed in Table 3. Internal averaging minimizes the effect of this noise when using longer scalar timeout multipliers. The effects of this noise are included in the overall accuracy of the devices as specified in the Electrical Characteristics.
Interfacing with a Microcontroller
Figure 5 shows the MAX6577 interfaced with an 8051 C. In this example, TS1 is tied to ground and TS0 is
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SOT Temperature Sensors with Period/Frequency Output MAX6576/MAX6577
VCC
+2.7V TO +5.5V
470 x 8 P1.0
0.1F
VDD
UNIVERSAL COUNTER OUT "PERIOD"
+2.7V TO +5.5V
P1.1 P1.2 P1.3 P1.4 P1.5 P1.6
TS0 TS1
MAX6576
VDD
0.1F
GND
TS0 TS1
MAX6577
OUT
T0
P1.7 22pF X1
Figure 3. MAX6576 Quick-Look Circuit
GND
8051
+2.7V TO +5.5V
GND X2
12MHz
22pF
VDD
0.1F UNIVERSAL COUNTER OUT "FREQUENCY"
TS0 TS1
MAX6577
Figure 5. Interfacing with a C
GND
Chip Information
TRANSISTOR COUNT: 302
Figure 4. MAX6577 Quick-Look Circuit
Table 3. Typical Peak Noise Amplitude
PARAMETER Scalar Multiplier Noise Amplitude (C) 10 0.38 MAX6576 40 0.17 160 0.11 640 0.094 4 0.13 1 0.066 MAX6577 1/4 0.040 1/16 0.028
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SOT Temperature Sensors with Period/Frequency Output MAX6576/MAX6577
Listing 1. 8051 Code Example
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SOT Temperature Sensors with Period/Frequency Output MAX6576/MAX6577
Listing 1. 8051 Code Example (continued)
Package Information
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.
8 _____________________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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