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

is driven by the MAX6691’s internal voltage reference

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

Four-Channel Thermistor Temperature-to-Pulse-

Width Converter

________________________________________________________________ Maxim Integrated Products

1

1

2

3

4

5

10

9

8

7

6

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

I/O

N.C.

GND

T4

T3

T2

T1

MAX6691

TOP VIEW

R+

R-

T4

T3

T2

T1

MICRO-

CONTROLLER

10k

Ω

Typical Application Circuit

19-2304; Rev 1; 2/07

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

PKG

CODE

MAX6691MUB

-55

°C to +125°C

10 µMAX

U10-2