Rainbow Electronics MAX6691 - Manual

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
♦ Simple Single-Wire Interface
♦ Measures Up to Four Thermistor Temperatures
♦ Low-Average Thermistor Current Minimizes Self-
Heating Errors
♦ Internal Voltage Reference Isolates Thermistor
from Power-Supply Noise
♦ Accommodates Any Thermistor Temperature
Range
MAX6691
Four-Channel Thermistor Temperature-to-Pulse-
Width Converter
________________________________________________________________ Maxim Integrated Products 1
1
2
3
4
5
10
9
8
7
6
V
CC
I/O
N.C.
GND T4
T3
T2
T1
MAX6691
µMAX
TOP VIEW
R+ R-
Pin Configuration
1
2
3
4
5
10
9
8
7
6
V CC
I/O
N.C.
GND T4
T3
T2
T1
MAX6691
TOP VIEW
R+ R-
T4
T3
T2
T1
MICRO-
CONTROLLER
10k Ω
V CC
R EXT
Typical Application Circuit
19-2304; Rev 0; 1/02
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.
Ordering Information
PART TEMP RANGE PIN-PACKAGE
MAX6691MUB -55 °C to +125°C 10 µMAX