QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 491

TEC TEMPERATURE CONTROLLER

LTC1923EUH

DESCRIPTION

Demonstration circuit 491 features the LTC1923EUH

thermoelectric cooler (TEC) controller. The LTC1923EUH

comes in a small 32-lead QFN package (5mm by 5mm).

Since the switching frequency of the circuit is 1MHz,

small size inductors and capacitors are used as output

filters. The main components are within a small assem-

bly area about 0.75” by 0.5”. DC491 provides a complete

temperature control solution for TEC based temperature

control of fiber-optic lasers. Laser temperature may be

controlled at temperatures above or below ambient with

set point stability typically well within 0.05°C over widely

varying ambient temperature. Temperature set point is

established with a potentiometer. Considerably more

detail relating to TEC temperature control issues is avail-

able in LTC Application Note AN-89, A Thermoelectric

Cooler Temperature Controller for Fiber Optic Lasers.

This publication should be reviewed before demo board

results are evaluated.

Design files for this circuit board are available. Call

the LTC factory.

QUICK START PROCEDURE

Demonstration circuit 491 is easy to set up to evaluate

the performance of the LTC1923EUH. Refer to Figure 1

for proper measurement equipment setup and follow the

procedure below:

1.

Connect a turned-off power supply (2.7–5.5V) to the

VDD and GND terminals.

2.

Connect a thermistor to the NTC+ and NTC– termi-

nals. Although the thermistor is not a polarized de-

vice, one of its leads may be committed to the lasers

case ground. If this is so, this lead should be con-

nected to NTC–. Shielded cable should be used for the

thermistor leads, with the shield connected to ground.

3.

Adjust the temperature set point potentiometer (R15)

using a small screwdriver.

4.

Connect the TEC leads from the laser to the boards

TEC+ and TEC– terminals. Observe polarity.

5.

Turn on the power supply. The board will typically pull

hundreds of milliamps for several seconds. Once the

temperature set point is reached the current drops

and settles to some sustaining value.

6.

Performance optimization for any particular laser is

achievable by following the procedures and guidelines

given in LTC Application Note AN-89.

+

–

+

–

TEC

LASER

THERMISTOR

+–

+

–

+–

Figure 1. Proper Measurement Equipment Setup

1