General Description

The MAX8520/MAX8521 are designed to drive thermo-

electric coolers (TECs) in space-constrained optical

modules. Both devices deliver ±1.5A output current

and control the TEC current to eliminate harmful current

surges. On-chip FETs minimize external components and

high switching frequency reduces the size of external

components.

The MAX8520 and MAX8521 operate from a single supply

and bias the TEC between the outputs of two synchro-

nous buck regulators. This operation allows for temper-

ature control without “dead zones” or other nonlinearities

at low current. This arrangement ensures that the control

system does not hunt when the set point is very close to

the natural operating point, requiring a small amount of

heating or cooling. An analog control signal precisely

sets the TEC current.

Both devices feature accurate, individually adjustable

heating current limit and cooling current limit, along

with maximum TEC voltage limit to improve the reliability

of optical modules. An analog output signal monitors

the TEC current. A unique ripple cancellation scheme

helps reduce noise.

The MAX8520 is available in a 5mm x 5mm thin QFN

package and its switching frequency is adjustable up to

1MHz through an external resistor. The MAX8521 is also

available in a 5mm x 5mm thin QFN, as well as a space-

saving 3mm x 3mm UCSP™, with a pin-selectable

switching frequency of 500kHz or 1MHz.

Applications

SFF/SFP Modules

Fiber-Optic Laser Modules

Fiber-Optic Network Equipment

ATE

Biotech Lab Equipment

Features

o Low-Profile Design

o On-Chip Power MOSFETs

o High-Efficiency Switch-Mode Design

o Ripple Cancellation for Low Noise

o Direct Current Control Prevents TEC Current

Surges

o 5% Accurate Adjustable Heating/Cooling Current

Limits

o 2% Accurate TEC Voltage Limit

o No Dead Zone or Hunting at Low Output Current

o ITEC Monitors TEC Current

o 1% Accurate Voltage Reference

o Switching Frequency Up to 1MHz

o Synchronization (MAX8521)

Smallest TEC Power Drivers for

Optical Modules

________________________________________________________________ Maxim Integrated Products

1

Ordering Information

19-2586; Rev 0; 10/02

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.

PART

TEMP RANGE

PIN-PACKAGE

MAX8520ETP

-40

°C to +85°C

20 Thin QFN 5mm x 5mm

MAX8521EBX

-40

°C to +85°C

36 UCSP 3mm x 3mm

MAX8521ETP

-40

°C to +85°C

20 Thin QFN 5mm x 5mm

UCSP is a trademark of Maxim Integrated Products, Inc.

INPUT

3V TO 5.5V

COMP

GND

SHDN

ITEC

ON

OFF

TEC CURRENT

MONITOR

CTLI

LX1

PGND1

CS

OS1

OS2

LX2

PGND2

TEC

± 1.5A

REF

CURRENT-

CONTROL

SIGNAL

FREQ

ANALOG /DIGITAL

TEMPERATURE CONTROL

OUTPUT

MAX8521

Typical Operating Circuit

Pin Configurations appear at end of data sheet.

3mm x 3mm

CSP

5mm x 5mm

QFN