MAX6691 Datasheet, PDF (1/7 Pages) Maxim Integrated Products – Four-Channel Thermistor Temperature-to-Pulse- Width Converter

19-2304; Rev 0; 1/02
Four-Channel Thermistor Temperature-to-Pulse-
Width Converter
General Description
The MAX6691 four-channel thermistor temperature-to-
pulse-width converter measures the temperatures of up
to four thermistors and converts them to a series of out-
put pulses whose widths are related to the thermistors’
temperatures. Each of the four thermistors and an
external fixed resistor (R_EXT) form a voltage-divider that
is driven by the MAX6691’s internal voltage reference
(V_REF). V_REF and the voltage across R_EXT are mea-
sured and converted to a pulse.
The MAX6691 has a single open-drain I/O pin that can
be readily connected to a variety of microcontrollers.
The microcontroller initiates a conversion by pulling the
I/O pin low and releasing it. When conversion is done,
the MAX6691 signals the end of conversion by pulling
the I/O pin low once again. The pulse corresponding to
the first thermistor is sent immediately after the release
of the I/O pin.
The on-chip power-management circuitry reduces the
average thermistor current to minimize errors due to
thermistor self-heating. Between conversions, the
MAX6691 falls into a 10µA (max) sleep mode, where
the voltage reference is disabled and the supply cur-
rent is at its minimum.
The MAX6691 is available in a 10-pin µMAX package
and is specified from -55°C to +125°C temperature
range.
Applications
HVAC
Home Appliances
Medical Devices
Features
o Simple Single-Wire Interface
o Measures Up to Four Thermistor Temperatures
o Low-Average Thermistor Current Minimizes Self-
Heating Errors
o Internal Voltage Reference Isolates Thermistor
from Power-Supply Noise
o Accommodates Any Thermistor Temperature
Range
PART
MAX6691MUB
Ordering Information
TEMP RANGE
-55°C to +125°C
PIN-PACKAGE
10 µMAX
Typical Application Circuit
TOP VIEW
T1 ₁
T2 ₂
T1
T3 ₃
T2
T4
4
T3
R-
5
T4
V_CC
MAX6691
R_EXT
V_CC
10
I/O
9
8 N.C.
7 ^GND
6 ^R+
10kΩ
MICRO-
CONTROLLER
Pin Configuration
TOP VIEW
T1 1
T2 2
T3 3
T4 4
R- 5
MAX6691
µMAX
10 V_CC
9 I/O
8 N.C.
7 GND
6 R+
________________________________________________________________ Maxim Integrated Products 1
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