MAX6682 Datasheet, PDF (1/9 Pages) Maxim Integrated Products – Thermistor-to-Digital Converter

19-2219; Rev 0; 2/02
Thermistor-to-Digital Converter
General Description
The MAX6682 converts an external thermistor’s temper-
ature-dependent resistance directly into digital form.
The thermistor and an external fixed resistor form a volt-
age-divider that is driven by the MAX6682’s internal
voltage reference. The MAX6682 measures the voltage
across the external resistor and produces a 10-bit +
sign output code dependent on that voltage.
The MAX6682 does not linearize the highly nonlinear
transfer function of a typical negative temperature coef-
ficient (NTC) thermistor, but it does provide linear out-
put data over limited temperature ranges when used
with an external resistor of the correct value. Over the
0° to +50°C temperature range, the MAX6682 produces
output data that is scaled to 8LSBs/°C (for 0.125°C res-
olution), provided that the correct thermistor and exter-
nal resistor values are used. Other temperature ranges
can be easily accommodated, but do not necessarily
yield data scaled to an even number of LSBs per
degree.
The 3-wire SPI™-compatible interface can be readily
connected to a variety of microcontrollers.
The MAX6682 is a read-only device, simplifying use in
systems where only temperature data is required.
Power-management circuitry reduces the average ther-
mistor current, minimizing self-heating. Between con-
versions, supply current is reduced to 21µA (typ). The
internal voltage reference is shut down between mea-
surements.
The MAX6682 is available in a small, 8-pin µMAX pack-
age and is specified over the -55°C to +125°C temper-
ature range.
HVAC
Medical Devices
Battery Packs/Chargers
Home Appliances
Applications
Pin Configuration appears at end of data sheet.
SPI is a trademark of Motorola, Inc.
Features
o Converts Thermistor Temperature to Digital Data
o Low Average Thermistor Current Minimizes Self-
Heating Errors
o Low Supply Current, 21µA (typ) Including 10kΩ
Thermistor Current
o Internal Voltage Reference Isolates Thermistor
from Power-Supply Noise
o 10-Bit Resolution
o Accommodates Any Thermistor Temperature
Range
o Output Data Scaled for Direct Temperature
Readings from 0°C to +50°C
o Simple SPI-Compatible Interface
o Small, 8-Pin µMAX Package
PART
MAX6682MUA
Ordering Information
TEMP RANGE
-55°C to +125°C
PIN-PACKAGE
8 µMAX
Typical Operating Circuit
3.3V
0.1µF
V_CC
R_EXT
THERMISTOR
R+
MAX6682
R-
CS
SCLK
GND
SO
MC68HCXX
I/O
SCLK
MISO
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