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PDF MAX6676AUT3-T Data sheet ( Hoja de datos )
| Número de pieza | MAX6676AUT3-T | |
| Descripción | Low-Voltage / 1.8kHz PWM Output Temperature Sensors | |
| Fabricantes | Maxim Integrated | |
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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 ✕ (t1 / t2) - 273.15
Where t1 is fixed with a typical value of 0.24ms and t2 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.
Applications
Process Control
Industrial
HVAC and Environmental Control
Automotive
Portable Devices
µP and µC Temperature Monitoring
Isolated Temperature Sensing
Features
o Simple Single-Wire, 1.8kHz PWM Output
o Operates Down to 1.8V
o High Accuracy
±1.5°C at TA = +25°C
±3.0°C at TA = 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
PART
MAX6676AUT3-T
MAX6676AUT5-T
MAX6677AUT3-T
Ordering Information
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
PART
MAX6676AUT3
MAX6676AUT5
MAX6677AUT3
Selector Guide
OUTPUT
TYPE
Open drain
Open drain
Push-pull
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
Pin Configuration
0.1µF
VCC
VCC
DOUT
MAX6676
GND
5.1kΩ*
t2
t1
INPUT TO
TIMER/COUNTER
µC
*REQUIRED ONLY FOR MAX6676.
TOP VIEW
DOUT 1
6 GND
MAX6676
GND 2 MAX6677 5 GND
VCC 3
4 GND
SOT23
________________________________________________________________ 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.
1 page  
Low-Voltage, 1.8kHz PWM Output Temperature
Sensors
PIN
1
2, 4, 5, 6
3
Pin Description
NAME
DOUT
GND
VCC
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 VCC to
GND with a 0.1µF capacitor.
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, t1 (low) and t2 (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 (t1 / t2) - 273.15
The µC or µP measures the output of the MAX6676/
MAX6677 by counting t1 and t2 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 t1 and t2 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.
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.
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.
t2
t1
Figure 1. MAX6676/MAX6677 PWM Output
VCC
VCC
P
DOUT
N
DOUT
N
(a)
MAX6677
Figure 2. Output Configurations
(b)
MAX6676
_______________________________________________________________________________________ 5
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