19-1484; Rev 0; 4/99
SOT Temperature Sensors with
Period/Frequency Output
General Description
The MAX6576/MAX6577 are low-cost, low-current tem-
perature 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 ±3°C at
+25°C, ±4.5°C at +85°C, and ±5°C at +125°C. The
MAX6577 offers accuracy of ±3°C at +25°C, ±3.5°C at
+85°C, and ±4.5°C at +125°C.
Both devices feature a single-wire output that minimizes
the number of pins necessary to interface with a micro-
processor. The period/frequency range of the output
square wave can be selected by hard-wiring the two
time-select pins (TS0, TS1) to either V
DD
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 (µs) (MAX6576)
Temperature to Frequency (Hz) (MAX6577)
o
±0.8°C Accuracy at +25°C (±3°C max)
o
No External Components
o
Operates from +2.7V to +5.5V Supply Voltage
o
Low 140µA Typical Supply Current
o
Standard Operating Temperature Range:
-40°C to +125°C
o
Small 6-Pin SOT23 Package
Features
MAX6576/MAX6577
Applications
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
MAX6576ZUT
-40°C to +125°C
MAX6577ZUT
-40°C to +125°C
PART
Ordering Information
TEMP. RANGE
PIN-
PACKAGE
6 SOT23
6 SOT23
SOT
TOP MARK
AABI
AABJ
Pin Configuration
TOP VIEW
+2.7V TO +5.5V
0.1µF
V
DD
1
6
OUT
Typical Operating Circuit
V
DD
0.1µF
V
CC
GND
2
MAX6576
MAX6577
5
TS1
MAX6576
MAX6577
TS1
TS0
GND
OUT
µP
GND
I/O
N.C.
3
4
TS0
SOT23-6
________________________________________________________________
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.
SOT Temperature Sensors with
Period/Frequency Output
MAX6576/MAX6577
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND)
V
DD
......................................................................-0.3V to +6V
TS1, TS0, OUT.......................................-0.3V to (V
DD
+ 0.3V)
Input/Output Current, All Pins...........................................±20mA
Continuous Power Dissipation (T
A
= +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
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
(V
DD
= +2.7V to +5.5V, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are specified at T
A
= +25°C and V
DD
= +5V,
unless otherwise noted.)
PARAMETER
V
DD
Range
Supply Current
SYMBOL
V
DD
I
DD
V
DD
= 5.5V
T
A
= -40°C to +85°C
T
A
= -40°C to +125°C
T
A
= -20°C
T
A
= 0°C
MAX6576
Temperature Sensor
Error (Note 1)
MAX6577
T
A
= +25°C
T
A
= +85°C
T
A
= +125°C
T
A
= -20°C
T
A
= 0°C
T
A
= +25°C
T
A
= +85°C
T
A
= +125°C
V
TS1
= GND, V
TS0
= GND
Output Clock Period
t
OUT
MAX6576,
T (temp) in °K,
Figure 1
V
TS1
= GND, V
TS0
= V
DD
V
TS1
= V
DD
, V
TS0
= GND
V
TS1
= V
DD
, V
TS0
= V
DD
V
TS1
= GND, V
TS0
= GND
Output Clock Frequency
f
OUT
MAX6577,
T (temp) in °K,
Figure 2
V
TS1
= GND, V
TS0
= V
DD
V
TS1
= V
DD
, V
TS0
= GND
V
TS1
= V
DD
, V
TS0
= V
DD
OUT Duty Cycle (Note 2)
Time-Select Pin Logic
Levels
V
IL
V
IH
V
OL
OUT Voltage
V
OH
V
DD
> 4.5V, I
SINK
= 3.2mA
V
DD
> 2.7V, I
SINK
= 1.2mA
V
DD
> 4.5V, I
SRC
= 800µA
V
DD
> 2.7V, I
SRC
= 500µA
2.3
0.4
0.3
V
DD
- 1.5
0.8V
DD
-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
µs
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
µA
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
(V
DD
= +5V, T
A
= +25°C, unless otherwise noted.)
TEMPERATURE ACCURACY
(T
A
= +25°C)
MAX6576 toc01
MAX6576/MAX6577
TEMPERATURE ACCURACY
(T
A
= +85°C)
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 (µA)
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
+100°C
+100°C
+12.5°C/div
+15°C/div
MOUNTED ON 0.75 in.
2
OF 2oz. COPPER
+25°C
5sec/div
20sec/div
MOUNTED ON 0.75 in.
2
OF 2oz. COPPER
+25°C
_______________________________________________________________________________________
3
SOT Temperature Sensors with
Period/Frequency Output
MAX6576/MAX6577
Pin Description
PIN
1
2
3
4, 5
6
NAME
V
DD
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 V
DD
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
V
DD
V
DD
TS0
GND
V
DD
GND
V
DD
SCALAR MULTIPLIER
(µs/°K)
10
40
160
640
Table 2. MAX6577 Time-Select Pin
Configuration
TS1
GND
GND
V
DD
V
DD
TS0
GND
V
DD
GND
V
DD
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(
µ
s)
scalar mulitplier(
µ
s/
°
K)
−
273.15
°
K
T(
°
C)
=
frequency(Hz)
scalar mulitplier(Hz/
°
K)
−
273.15
°
K
Detailed Description
The MAX6576/MAX6577 low-cost, low-current (140µA
typ) temperature sensors are ideal for interfacing with
microcontrollers (µCs) or microprocessors (µPs). The
MAX6576 converts ambient temperature into a 50% duty-
cycle square wave with a period proportional to absolute
temperature. The MAX6577 converts ambient tempera-
ture 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 interfac-
ing with a µP.
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 tempera-
ture to frequency. The output of the device is a free-
running, 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 out-
put 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 tempera-
ture to period. The output of the device is a free-
running, 50% duty-cycle square wave with a period that
4
_______________________________________________________________________________________
SOT Temperature Sensors with
Period/Frequency Output
MAX6576/MAX6577
MAX6576
CLOCK WAVEFORM OUTPUT
MAX6577
CLOCK WAVEFORM OUTPUT
t
OUT
t
OUT
f
OUT
= 1 / t
OUT
f
OUT
(°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 10µs/°K. The MAX6576 converts the ambi-
ent temperature into a square wave with a period that is
10 times the absolute temperature of the device in µs.
At room temperature, the universal counter will display
approximately 2980µs.
Figure 4 shows a quick-look application circuit for the
MAX6577 using a universal counter measuring frequen-
cy. TS1 is tied to ground and TS0 is tied to V
DD
to
select a scalar multiplier of 1Hz/°K. The MAX6577 con-
verts 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 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. The 8051
µC 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 pro-
vides the code for this application. The interface is simi-
lar for the MAX6576, except the µC 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
0.1µF ceramic bypass capacitor close to the supply pin
of the devices. Internal noise is inherent in the opera-
tion 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
µC. In this example, TS1 is tied to ground and TS0 is
_______________________________________________________________________________________
5
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