General Description

The MAX1978/MAX1979 are the smallest, safest, most

accurate complete single-chip temperature controllers for

Peltier thermoelectric cooler (TEC) modules. On-chip power

FETs and thermal control-loop circuitry minimize external

components while maintaining high efficiency. Selectable

500kHz/1MHz switching frequency and a unique ripple-can-

cellation scheme optimize component size and efficiency

while reducing noise. Switching speeds of internal

MOSFETs are optimized to reduce noise and EMI. An ultra-

low-drift chopper amplifier maintains ±0.001°C temperature

stability. Output current, rather than voltage, is directly con-

trolled to eliminate current surges. Individual heating and

cooling current and voltage limits provide the highest level of

TEC protection.

The MAX1978 operates from a single supply and provides

bipolar ±3A output by biasing the TEC between the outputs

of two synchronous buck regulators. True bipolar operation

controls temperature without “dead zones” or other nonlin-

earities at low load currents. The control system does not

hunt when the set point is very close to the natural operating

point, where only a small amount of heating or cooling is

needed. An analog control signal precisely sets the TEC

current. The MAX1979 provides unipolar output up to 6A.

A chopper-stabilized instrumentation amplifier and a high-

precision integrator amplifier are supplied to create a pro-

portional-integral (PI) or proportional-integral-derivative (PID)

controller. The instrumentation amplifier can interface to an

external NTC or PTC thermistor, thermocouple, or semicon-

ductor temperature sensor. Analog outputs are provided to

monitor TEC temperature and current. In addition, separate

overtemperature and undertemperature outputs indicate

when the TEC temperature is out of range. An on-chip volt-

age reference provides bias for a thermistor bridge.

The MAX1978/MAX1979 are available in a low-profile

48-lead thin QFN-EP package and is specified over the

-40°C to +85°C temperature range. The thermally

enhanced QFN-EP package with exposed metal pad

minimizes operating junction temperature. An evaluation

kit is available to speed designs.

Applications

Fiber Optic Laser Modules

WDM, DWDM Laser-Diode Temperature Control

Fiber Optic Network Equipment

EDFA Optical Amplifiers

Telecom Fiber Interfaces

ATE

Features

o Smallest, Safest, Most Accurate Complete

Single-Chip Controller

o On-Chip Power MOSFETS—No External FETs

o Circuit Height < 3mm

o Temperature Stability to 0.001°C

o Integrated Precision Integrator and Chopper

Stabilized Op Amps

o Accurate, Independent Heating and Cooling

Current Limits

o Eliminates Surges By Directly Controlling

TEC Current

o Adjustable Differential TEC Voltage Limit

o Low-Ripple and Low-Noise Design

o TEC Current Monitor

o Temperature Monitor

o Over- and Undertemperature Alarm

o Bipolar ±3A Output Current (MAX1978)

o Unipolar +6A Output Current (MAX1979)

Integrated Temperature

Controllers for Peltier Modules

________________________________________________________________ Maxim Integrated Products

1

Ordering Information

FREQ

N.C.

LX1

PGND1

N.C.

LX1

GND

GND

LX1

PGND1

PGND2

LX2

PGND2

LX2

N.C.

LX2

N.C.

OS2

1

2

3

4

5

6

7

8

9

10

11

12

36

35

34

33

32

31

30

29

28

27

26

25

QFN-EP

MAX1978

MAX1979

TOP VIEW

*ELECTRICALLY CONNECTED TO THE UNDERSIDE METAL SLUG.

NOTE: GND IS CONNECTED TO THE UNDERSIDE METAL SLUG.

OT

SHDN

Pin Configuration

19-2490; Rev 0; 7/02

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.

Typical Operating Circuit appears at end of data sheet.

EVALUATION

KIT

AVAILABLE

PART

TEMP RANGE

PIN-PACKAGE

MAX1978ETM

-40

°C to +85°C

48 Thin QFN-EP*

MAX1979ETM

-40

°C to +85°C

48 Thin QFN-EP

*EP = Exposed pad.