19-2660; Rev 1; 1/03
Low-Voltage, 1.8kHz PWM Output Temperature
Sensors
General Description
The MAX6676/MAX6677 are high-accuracy, low-power
temperature sensors with a single-wire output. The
MAX6676/MAX6677 convert the ambient temperature
into a ratiometric PWM output with temperature informa-
tion contained in the duty cycle of the output square
wave. The MAX6676 has an open-drain output and the
MAX6677 has a push-pull output.
The MAX6676/MAX6677 are specified for operation with
power-supply voltages from 1.8V to 3.6V, or from 3.6V to
5.5V (MAX6676 only). The typical unloaded supply cur-
rent is 80µA. All devices feature a single-wire output that
minimizes the number of pins necessary to interface
with a microprocessor (µP). The output is a square wave
with a nominal frequency of 1.8kHz (±20%) at +25°C.
The output format is decoded as follows:
Temperature (°C) = 398.15
✕
(t
1
/ t
2
) - 273.15
Where t
1
is fixed with a typical value of 0.24ms and t
2
is
modulated by the temperature. The MAX6676/
MAX6677 operate from -40°C to +125°C and are avail-
able in space-saving 6-pin SOT23 packages.
Features
o
Simple Single-Wire, 1.8kHz PWM Output
o
Operates Down to 1.8V
o
High Accuracy
±1.5°C at T
A
= +25°C
±3.0°C at T
A
= 0°C to +85°C
o
Operates from -40°C to +125°C
o
Low 80µA Typical Current Consumption
o
Small 6-Pin SOT23 Package
MAX6676/MAX6677
Ordering Information
PART
MAX6676AUT3-T
MAX6676AUT5-T
MAX6677AUT3-T
TEMP
RANGE
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
PIN-
PACKAGE
6 SOT23-6
6 SOT23-6
6 SOT23-6
Applications
Process Control
Industrial
HVAC and Environmental Control
Automotive
Portable Devices
µP and µC Temperature Monitoring
Isolated Temperature Sensing
MAX6676AUT3
MAX6676AUT5
MAX6677AUT3
Open drain
Open drain
Push-pull
PART
OUTPUT
TYPE
Selector Guide
SUPPLY
VOLTAGE
RANGE (V)
1.8 to 3.6
3.6 to 5.5
1.8 to 3.6
TOP
MARK
ABBF
ABBG
ABBH
Typical Operating Circuit
V
CC
Pin Configuration
TOP VIEW
V
CC
DOUT
0.1µF
5.1kΩ*
INPUT TO
TIMER/COUNTER
t
2
t
1
µC
DOUT
1
6
GND
MAX6676
GND
2
MAX6676
MAX6677
5
GND
GND
V
CC
3
4
GND
SOT23
*REQUIRED ONLY FOR MAX6676.
________________________________________________________________
Maxim Integrated Products
1
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.
Low-Voltage, 1.8kHz PWM Output Temperature
Sensors
MAX6676/MAX6677
ABSOLUTE MAXIMUM RATINGS
(Voltages Referenced to GND)
V
CC
........................................................................-0.3V to +6.0V
DOUT (MAX6676)..................................................-0.3V to +6.0V
DOUT (MAX6677).......................................-0.3V to (V
CC
+ 0.3V)
DOUT Current .....................................................-1mA to +50mA
ESD Protection (DOUT, Human Body Model) .................±2000V
Continuous Power Dissipation (T
A
= +70°C)
6-Pin SOT23 (derate 8.7mW/°C above +70°C).........695.7mW
Operating Temperature Range .........................-40°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
Junction Temperature ......................................................+150°C
Lead Temperature (soldering, 10s) .................................+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
CC
= 1.8V to 3.6V (MAX6676AUT3/MAX6677AUT3), V
CC
= 3.6V to 5.5V (MAX6676AUT5), T
A
= -40°C to +125°C, unless otherwise
noted. Typical values are at V
CC
= 3.0V (MAX6676AUT3/MAX6677AUT3), V
CC
= 5.0V (MAX6676AUT5), T
A
= +25°C.)
PARAMETER
Supply Voltage Range
Supply Current
SYMBOL
V
CC
I
CC
MAX6676AUT5
R
L
=
∞
T
A
= +25°C
Temperature Error
T
A
= 0°C to +85°C
T
A
= -20°C to +100°C
T
A
= -40°C to +125°C
Nominal t
1
Pulse Width
Output High Voltage
Output Leakage Current
Output Low Voltage
Fall Time
Rise Time
Digital Output Capacitance
Power-Supply Rejection Ratio
V
OL
t
F
t
R
C
OUT
PSRR
V
CC
= 1.8V - 3.6V
-1.2
V
OH
I
OH
= 800µA, MAX6677
V
OUT
= V
CC
I
OL
= 3mA
C
L
= 100pF, R
L
= 10kΩ
MAX6676, C
L
= 15pF, R
L
= 10kΩ
MAX6677, C
L
= 100pF, R
L
= 10kΩ
20
300
30
15
+0.4
+1.2
V
CC
-
0.3
0.1
0.3
-1.5
-3.0
-4.2
-5.5
240
CONDITIONS
MAX6676AUT3/MAX6677AUT3
MIN
1.8
3.6
80
TYP
MAX
3.6
5.5
200
+1.5
+3.0
+4.2
+5.5
µs
V
µA
V
ns
ns
pF
°C/V
°C
UNITS
V
µA
Note 1:
Parts are tested at +25°C. Specifications are guaranteed by design over temperature.
2
_______________________________________________________________________________________
Low-Voltage, 1.8kHz PWM Output Temperature
Sensors
Typical Operating Characteristics
(V
CC
= 3.0V, T
A
= +25°C, unless otherwise noted.)
OUTPUT FREQUENCY
vs. TEMPERATURE
MAX6676 toc01
MAX6676/MAX6677
MAX6676AUT3 OUTPUT FREQUENCY
vs. SUPPLY VOLTAGE
MAX6676 toc02
t
1
AND t
2
TIMES
vs. TEMPERATURE
MAX6676 toc03
3.0
2.50
450
t
2
OUTPUT FREQUENCY (kHz)
400
OUTPUT FREQUENCY (Hz)
2.5
2.25
TIME (µs)
TEMP = +125°C
2.00
TEMP = +25°C
1.75
TEMP = -40°C
250
t
1
350
2.0
300
1.5
1.0
-40
-15
10
35
60
85
110
TEMPERATURE (°C)
1.50
1.8
2.1
2.4
2.7
3.0
3.3
3.6
SUPPLY VOLTAGE (V)
200
-40
-15
10
35
60
85
110
TEMPERATURE (°C)
OUTPUT ACCURACY
vs. TEMPERATURE
MAX6676 toc04
MAX6676AUT3 SUPPLY CURRENT
vs. TEMPERATURE
MAX6676 toc05
MAX6676AUT3 SUPPLY CURRENT
vs. SUPPLY VOLTAGE
400
SUPPLY CURRENT (µA)
350
300
250
200
150
100
5.1kΩ PULLUP
MAX6676 toc06
5
600
500
SUPPLY CURRENT (µA)
400
300
V
CC
= 3.0V
200
100
5.1kΩ PULLUP RESISTOR
V
CC
= 1.8V
V
CC
= 3.6V
450
OUTPUT ACCURACY (°C)
3
1
-1
-3
50
0
1.8
NO PULLUP
2.1
2.4
2.7
3.0
3.3
3.6
-5
-40
-15
10
35
60
85
110
TEMPERATURE (°C)
0
-40
-15
10
35
60
85
110
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
POWER-SUPPLY REJECTION RATIO
vs. TEMPERATURE
MAX6676 toc07
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX6676 toc08
OUTPUT FALL TIME
(C
L
= 100pF, R
L
= 100kΩ)
MAX6676 toc09
1.0
2
1
CHANGE IN TEMPERATURE (°C)
0
-1
-2
-3
-4
-5
0.5
PSRR (°C/V)
0
1V/div
-0.5
0V
V
AC
= 100mV
P-P
1
10
100
FREQUENCY (Hz)
1k
10k
10ns/div
-1.0
-50
-25
0
25
50
75
100
125
TEMPERATURE (°C)
-6
_______________________________________________________________________________________
3
Low-Voltage, 1.8kHz PWM Output Temperature
Sensors
MAX6676/MAX6677
Typical Operating Characteristics (continued)
(V
CC
= 3.0V, T
A
= +25°C, unless otherwise noted.)
MAX6677 OUTPUT RISE TIME
MAX6676 toc10
MAX6677 OUTPUT RISE AND FALL TIMES
vs. CAPACITIVE LOAD
MAX6676 toc11
200
C
LOAD
= 100pF
R
L
= 100kΩ
160
1V/div
TIME (ns)
120
RISE
80
0
40
FALL
0
40ns/div
0
100
200
300
C
LOAD
(pF)
400
500
600
MAX6677 OUTPUT HIGH VOLTAGE
vs. TEMPERATURE
MAX6676 toc12
MAX6677 OUTPUT LOW VOLTAGE
vs. TEMPERATURE
MAX6676 toc13
3.50
I
SOURCE
= 800µA
OUTPUT HIGH VOLTAGE (V)
3.25
350
300
OUTPUT LOW VOLTAGE (mV)
250
200
150
100
50
I
SINK
= 1.5mA
I
SINK
= 5mA
3.00
2.75
I
SINK
= 1mA
2.50
-40
-15
10
35
60
85
110
TEMPERATURE (°C)
0
-40
-5
30
65
100
TEMPERATURE (°C)
4
_______________________________________________________________________________________
Low-Voltage, 1.8kHz PWM Output Temperature
Sensors
Pin Description
PIN
1
NAME
DOUT
FUNCTION
Digital Output Pin. The duty
cycle of the output waveform is
modulated by temperature.
Ground. All four ground pins
must be connected to GND.
Supply Voltage. Bypass V
CC
to
GND with a 0.1µF capacitor.
Applications Information
Accurate temperature monitoring requires a good ther-
mal contact between the MAX6676/MAX6677 and the
object being monitored. A precise temperature mea-
surement depends on the thermal resistance between
the object being monitored and the MAX6676/
MAX6677 die. Heat flows in and out of plastic pack-
ages primarily through the leads. If the sensor is intend-
ed to measure the temperature of a heat-generating
component on the circuit board, mount the device as
close as possible to that component and share the
ground traces (if they are not too noisy) with the com-
ponent. This maximizes the heat transfer from the com-
ponent to the sensor.
MAX6676/MAX6677
2, 4, 5, 6
3
GND
V
CC
Detailed Description
The MAX6676/MAX6677 are high-accuracy, low-current
(80µA, typ) temperature sensors ideal for interfacing
with µCs or µPs. The MAX6676/MAX6677 convert the
ambient temperature into a ratiometric PWM output at a
nominal frequency of 1.8kHz (±20%) at +25°C.
The time periods, t
1
(low) and t
2
(high) (Figure 1), are
easily read by a µP’s timer/counter port. To calculate
the temperature, use the following expression:
Temperature (°C) = 398.15 x (t
1
/ t
2
) - 273.15
The µC or µP measures the output of the MAX6676/
MAX6677 by counting t
1
and t
2
and computing the
temperature based on their ratio. The resolution of the
count is a function of the processor clock frequency
and the resolution of the counter. Always use the same
clock for t
1
and t
2
counters so that the temperature is
strictly based on a ratio of the two times, thus eliminat-
ing errors due to different clocks’ frequencies.
The MAX6677 (Figure 2a) has a push-pull output with
full CMOS output swings. The ability to source and sink
current allows the MAX6677 to drive capacitive loads
up to 100pF with less than 1°C error.
The MAX6676 (Figure 2b) has an open-drain output.
The output capacitance should be minimized in
MAX6676 applications because the sourcing current is
set by the pullup resistor. If the output capacitance
becomes too large, lengthy rise and fall times distort
the pulse width, resulting in inaccurate measurements.
Power Supply from µP Port Pin
The low quiescent current of the MAX6676/MAX6677
enables them to be powered from a logic line, which
meets the requirements for supply voltage range. This
provides a simple shutdown function to totally eliminate
quiescent current by taking the logic line low. The logic
line must be able to withstand the 0.1µF power-supply
bypass capacitance.
t
2
t
1
Figure 1. MAX6676/MAX6677 PWM Output
V
CC
V
CC
P
DOUT
N
N
DOUT
(a)
MAX6677
(b)
MAX6676
Figure 2. Output Configurations
_______________________________________________________________________________________
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