DC491A Analog Devices

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 491 TEC TEMPERATURE CONTROLLER LTC1923EUH DESCRIPTION Demonstration circuit 491 features the LTC1923EUH set point stability typically well within 0.05C over widely thermoelectric cooler (TEC) controller. The LTC1923EUH varying ambient temperature. Temperature set point is comes in a small 32-lead QFN package (5mm by 5mm). established with a potentiometer. Considerably more Since the switching frequency of the circuit is 1MHz, detail relating to TEC temperature control issues is avail- small size inductors and capacitors are used as output able in LTC Application Note AN-89, A Thermoelectric filters. The main components are within a small assem- Cooler Temperature Controller for Fiber Optic Lasers. bly area about 0.75 by 0.5. DC491 provides a complete This publication should be reviewed before demo board temperature control solution for TEC based temperature results are evaluated. control of fiber-optic lasers. Laser temperature may be Design files for this circuit board are available. Call controlled at temperatures above or below ambient with the LTC factory. QUICK START PROCEDURE Demonstration circuit 491 is easy to set up to evaluate 3. Adjust the temperature set point potentiometer (R15) the performance of the LTC1923EUH. Refer to Figure 1 using a small screwdriver. for proper measurement equipment setup and follow the 4. Connect the TEC leads from the laser to the boards procedure below: TEC+ and TEC terminals. Observe polarity. 1. Connect a turned-off power supply (2.75.5V) to the 5. Turn on the power supply. The board will typically pull VDD and GND terminals. hundreds of milliamps for several seconds. Once the 2. Connect a thermistor to the NTC+ and NTC termi- temperature set point is reached the current drops nals. Although the thermistor is not a polarized de- and settles to some sustaining value. vice, one of its leads may be committed to the lasers 6. Performance optimization for any particular laser is case ground. If this is so, this lead should be con- achievable by following the procedures and guidelines nected to NTC. Shielded cable should be used for the given in LTC Application Note AN-89. thermistor leads, with the shield connected to ground. ++ + LASER THERMISTOR TEC Figure 1. Proper Measurement Equipment Setup 1 + +5 4 3 2 1 TEC SUPPLY R1 C1 2.2K VDDF VSET C2 C3 0.1uF C4 R25 D VDDF R2 D U1 10K 0.1uF LTC1923EUH 330pF OPEN 0.1uF R3 R4 30 29 VSET VDDF PLLPF RT C5 10K 2.2K R24 31 28 VDD U2 RSLEW CT 0.1% R5 TP3 8 4 1 VDD SHDN/SYNC 0 C8 10K 1% LTC2053CMS8 32 27 1uF C6 C7 SDSYNCB VREF 3 + TP1 TP2 10uF 7 1 24 6.3V CNTRL PDRVB 2 - 0.1uF 0.1uF 2 23 4 2 TEC+ TEC- EAOUT NDRVB R6 C9 VDDF Q1-2 5 6 R7 C10 VDD 3 22 Q1-1 9.09K 0.1uF R8 FB VDD C11 TEC 10M Si5915DC 4.7uF VSET 1% SM Film Si5915DC 4 21 0.1uF R9 C12 L1 1% 6.3V AGND VDD 2.2 L2 SM Film 1uF 6 20 100K SS PGND RT1 TP4 R10 4.2uH 4.2uH C13 7 19 1% ILIM NDRVA C15 NTC+ 1uF C14 VSET Q2-2 1K Q2-1 C16 1% 8 18 10uF VSET PDRVA 10uF 2 Si5904DC 4 Si5904DC 6.3V 9 17 6.3V TP5 FAULTB CS+ 10uF R11 C17 10 16 NTC- R12 R13 VTHRM CS- 6.3V 0.1uF 0.02 11 15 10K 47.5K H/C ITEC C C 0.25W 1% C18 1% 12 14 1% VTEC TEC+ 0.1uF 26 13 N/C TEC- VSET 25 5 N/C N/C R14 TP7 10K TP6 ITEC 0.1% VTEC TP8 GND R15 20K 2 TEMP. ADJ. FAULT VDDF D1 VDDF R17 R16 10K C19 200 VDDF LED(Red) 0.1uF 0.1% R18 VDD SM Film Q3 100K B B TP9 1 2N7002 R19 VDD 100K 2.7-5.5V Q4 C20 1 2N7002 Heat 22uF VDDF D2 10V R20 GND 200 LED(Orn) TP10 Cool VDDF VDDF D3 R21 R22 200 VDDF LED(Grn) 100K Q5 1 2N7002 R23 100K CONTRACT NO. 1630 McCarthy Blvd. Milpitas, CA 95035 A Q6 A Phone: (408)432-1900 1 APPROVALS DATE Fax: (408)434-0507 2N7002 TECHNOLOGY DRAWN June Wu 1/10/02 TITLE CHECKED APPROVED LTC1923EUH, TEC Temperature Controller ENGINEER Wei Chen 1/10/02 SIZE CAGE CODE DWG NO REV DESIGNER DC491A A Friday, April 05, 2002 SCALE: FILENAME: SHEET 1 OF 1 5 4 3 2 1 1 3 CW 2 3 2 3 2 3 2 3 1 7 5 3 8 6 6 8 3 5 7 1 +