LTC1923 High Efficiency Thermoelectric U Cooler Controller FEATURESDESCRIPTIO ■ High Efficiency, Low Noise Topology The LTC®1923 is a pulse width modulator intended for ■ Adjustable Output Slew Rate Reduces EMI thermoelectric cooler (TEC) or heater applications requir- ■ Full-Bridge Controller for Bidirectional ing either unidirectional or bidirectional drive circuits. All Current Control of the necessary control circuitry and two sets of comple- ■ Adjustable Pulse-by-Pulse Bidirectional TEC mentary output drivers are integrated into the LTC1923 to Current Limit drive a full bridge, providing an efficient means of bidirec- ■ Open/Shorted Thermistor Indication tional current flow to the TEC. An accurate temperature ■ Solution Footprint in Less Than 0.6" × 0.8" control loop to stabilize the temperature of a laser diode (Double-Sided PCB) system is easily achieved with the addition of just a few ■ Available in 5mm x 5mm QFN and external components. Typical temperature setpoint accu- 28-Pin SSOP Packages racy of 0.1°C is achievable with the LTC1923. Adding an ■ TEC Voltage Clamping instrumentation amplifier front end allows setpoint stabil- ■ TEC Current, Voltage and Heat/Cool Status Outputs ity of 0.01°C. ■ Adjustable/Synchronizable Oscillator Frequency The part features independent adjustable heating and Reduces Filter Component Size and System Noise cooling pulse-by-pulse current limit, current soft-start for ■ 2.5V Reference Voltage Output controlled start-up, output slew rate control to reduce ■ 2.7V Minimum Operating Voltage system noise, differential current sense and voltage am- U plifiers and a host of auxiliary circuits to protect the laser APPLICATIO S and provide redundant system monitoring. ■ Laser-Based Fiber Optic Links , LTC and LT are registered trademarks of Linear Technology Corporation. ■ Medical Instruments ■ CPU Temperature Regulators UTYPICAL APPLICATIOLaser Temperature Control Loop Achieving Setpoint Stability of 0.01 ° C 10k 10k 0.1% PLLLPF RT 330pF 82k RSLEW CT + 1µF REF REF V V DD REF LTC2053 VDD SDSYNC VREF A = 10 TMP 10k LTC1658 VOUT – CMD NTC CNTRL PDRVB 10µF 4.7µF EAOUT NDRVB MPA* MPB** 10M L1 L2 100k 10µH COOLER 10µH FB VDD TEC LTC1923 1µF C1 C2 AGND PGND MNB** 22µF 22µF 1µF SS NDRVA MNA* 3 ILIM PDRVA 1 V RS SET CS+ 2 4 FAULT CS– VTHRM ITEC C1, C2: TAIYO YUDEN JMK325BJ226MM-T (X7R) L1, L2: SUMIDA CDRH6D2B-220NC H/C TEC+ *MNA, MPA: SILICONIX Si9801 V 1923 TA01 TEC TEC– **MNB, MPB: SILICONIX Si9801 1923f 1