LTC1923 High Efficiency Thermoelectric Cooler Controller DESCRIPTIO FEATURES n The LTC 1923 is a pulse width modulator intended for High Efficiency, Low Noise Topology n thermoelectric cooler (TEC) or heater applications requir- Adjustable Output Slew Rate Reduces EMI n Full-Bridge Controller for Bidirectional ing either unidirectional or bidirectional drive circuits. All of the necessary control circuitry and two sets of comple- Current Control n mentary output drivers are integrated into the LTC1923 to Adjustable Pulse-by-Pulse Bidirectional TEC Current Limit drive a full bridge, providing an efficient means of bidirec- n tional current flow to the TEC. An accurate temperature Open/Shorted Thermistor Indication n control loop to stabilize the temperature of a laser diode Solution Footprint in Less Than 0.6 0.8 (Double-Sided PCB) system is easily achieved with the addition of just a few n external components. Typical temperature setpoint accu- Available in 5mm x 5mm QFN and racy of 0.1 C is achievable with the LTC1923. Adding an 28-Pin SSOP Packages n TEC Voltage Clamping instrumentation amplifier front end allows setpoint stabil- n ity of 0.01 C. TEC Current, Voltage and Heat/Cool Status Outputs n 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 n 2.5V Reference Voltage Output controlled start-up, output slew rate control to reduce n 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. n Laser-Based Fiber Optic Links , LTC and LT are registered trademarks of Linear Technology Corporation. n Medical Instruments n CPU Temperature Regulators TYPICAL APPLICATIO Laser Temperature Control Loop Achieving Setpoint Stability of 0.01 C 10k 10k 0.1% PLLLPF R T 330pF 82k R C SLEW T + 1F REF REF V DD V REF LTC2053 V SDSYNC V DD REF A = 10 TMP 10k LTC1658 V OUT CMD NTC CNTRL PDRVB 10F 4.7F EAOUT NDRVB MPA* MPB** 10M L1 L2 100k COOLER 10H 10H FB V DD TEC LTC1923 1F C2 C1 AGND PGND MNB** 22F 22F 1F SS NDRVA MNA* 3 I PDRVA LIM 1 + R S V CS SET 2 4 FAULT CS V I THRM TEC C1, C2: TAIYO YUDEN JMK325BJ226MM-T (X7R) + L1, L2: SUMIDA CDRH6D2B-220NC H/C TEC *MNA, MPA: SILICONIX Si9801 1923 TA01 V TEC TEC **MNB, MPB: SILICONIX Si9801 1923f 1 U ULTC1923 ABSOLUTE AXI U RATI GS (Note 1) V to GND................................................. 0.3V to 6V FAULT, H/C ................................................. 0.3V to 6V DD SDSYNC, R ......................................... 0.3V to 6V Operating Temperature Range (Note 2) .. 40 C to 85 C SLEW FB, CNTRL, V , I , V ..................... 0.3V to 6V Storage Temperature Range ................. 65 C to 125 C THRM LIM SET + + CS , CS , TEC , TEC .................................0.3V to 6V Lead Temperature (Soldering, 10 sec).................. 300 C UUW PACKAGE/ORDER I FOR ATIO TOP VIEW ORDER PART ORDER PART NUMBER NUMBER PLLLPF 1 28 R T R 2 27 C T SLEW 32 31 30 29 28 27 26 25 LTC1923EUH LTC1923EGN SDSYNC 3 26 V REF CNTRL 1 PIN 1 24 PDRVB TOP VIEW CNTRL 4 25 PDRVB EAOUT 2 23 NDRVB EAOUT 5 24 NDRVB FB 3 22 V DD FB 6 23 V DD AGND 4 21 V DD AGND 7 22 PGND NC 5 20 PGND SS 8 21 NDRVA SS 6 19 NDRVA I 7 18 PDRVA I 9 20 PDRVA LIM LIM + + V 8 17 CS V 10 19 CS SET SET 9 10 11 12 13 14 15 16 FAULT 11 18 CS V 12 17 I TEC THRM + H/C 13 16 TEC UH PACKAGE V 14 15 TEC TEC 32-LEAD PLASTIC QFN T = 125 C, q = 34 C/W GN PACKAGE JMAX JA 28-LEAD PLASTIC SSOP EXPOSED PAD IS PGND (MUST BE SOLDERED TO PCB) T = 125 C, q = 120 C/W JMAX JA Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The l denotes specifications which apply over the full operating temperature range, otherwise specifications are T = 25 C. A V = 5V, R = V , SDSYNC = V , R = 10k, C = 330pF unless otherwise noted. DD SLEW DD DD T T SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Input Supply VDD Operating Supply Voltage l 2.7 5.5 V UVLO Undervoltage Lockout Low to High Threshold l 2.6 2.7 V UVHYST Hysteresis High to Low l 50 130 mV I Operating Supply Current No Output Load, Outputs Not Switching 2 4 mA DD I Shutdown I SDSYNC = 0V 10 25 m A DDSHDN DD SHDNTH Shutdown Threshold Measured at PDRVA, PDRVB 0.3 0.8 1.4 V 1923f 2 FAULT SDSYNC V R THRM SLEW H/C PLLLPF V R TEC T TEC C T + TEC V REF I NC TEC CS NC U WWW