DC1896A

DEMO CIRCUIT 1896A LTC3633AEFE-3 DEMO BOARD MANUAL DESCRIPTION LTC3633AEFE-3 DUAL CHANNEL 3A 20V MONOLITHIC SYNCHRONOUS STEP-DOWN REGULATOR BOARD Demonstration circuit DC1896 is a dual output regulator consisting of two constant-frequency step-down converters, based on the LTC3633A-3 monolithic dual channel synchronous buck regulator. The DC1896 has an input voltage range of 3.6V to 20V, with each regulator capable of delivering up to 3A of output current. The DC1896 can operate in either Burst Mode or forced continuous mode. In shutdown, the DC1896 can run off of less than 15 uA total. The DC1896 is a very efficient circuit: up to 90%. The DC1896 uses the 28 Pin QFN LTC3633AEFE-3 package, which has an exposed pad on the bottom-side of the IC for better thermal performance. These features, plus a programmable operating frequency range from 500 kHz to 4 MHz (2 MHz switching frequency with the RT pin connected to INTVcc), make the DC1896 demo board an ideal circuit for use industrial or distributed power applications. Design files for this circuit are available at www.linear.com/demo. QUICK START PROCEDURE The DC1896 is easy to set up to evaluate the performance of the LTC3633A-3. For a proper measurement equipment configuration, set up the circuit according to the diagram in Figure 1. NOTE: When measuring the input or output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. Measure the input or output voltage ripple by touching the probe tip directly across the Vin or Vout and GND terminals. See the proper scope probe technique in figure 2. soft-start (SS) positions of headers JP3 and JP4, shunt XJP8 into the forced continuous mode (FCM) position of MODE header JP8, shunt XJP14 into the 1 MHz position of the frequency (FREQ) header JP14, shunts XJP12 and XJP13 into the external (EXT) compensation positions of headers JP12 and JP13, and shunt XJP6 into the Vout1 voltage options of choice of header JP6: 1.5V, 1.8V, or 2.5V, and a shunt into the Vout2 voltage option of choice: 2.5V (header JP15), 3.3V (header JP5), or 5V (header JP7). Please follow the procedure outlined below for proper operation. 1. Connect the input power supply to the Vin1/Vin2 and GND terminals (Vin1 and Vin2 are separate nodes.). Connect the loads between the Vout and GND terminals. Refer to figure 1 for the proper measurement equipment setup. 2. Apply 5.5V at Vins 1 & 2. Measure both Vouts; they should read 0V. If desired, one can measure the shutdown supply current at this point. The supply current will be less than 15 uA in shutdown. Before proceeding to operation, insert jumper shunts XJP1 and XJP2 into the OFF positions of headers JP1 and JP2, shunt XJP11 into the ON position (180°out-of-phase) of PHASE header JP11, shunts XJP3 and XJP4 into the 3. Turn on Vout1 and Vout2 by shifting shunts XJP1 and XJP2 from the OFF positions to the ON positions. Both output voltages should be within a tolerance of +/- 2%. 4. Vary the input voltages from 5.8V (the min. Vin is dependent on Vout) to 20V, and the load currents from 0 to 3A. Both output voltages should be within +/- 3% tolerance. 1 LTC3633AEFE-3 5. Set the load current of both outputs to 3A and the input voltages to 20V, and then measure each output ripple voltage (refer to figure 2 for proper measurement technique); they should each measure less than 30 mVAC. Also, observe the voltage waveform at either switch node (pins 23 & 24 for reg.1 and 13 & 14 for reg.2) of each regulator. The switching frequencies should be between 800 kHz and 1.2 MHz (T = 1.25 us and 0.833 us). To attain 2 MHz operation, change the shunt position on header JP14. In all cases, both switch node waveforms should be rectangular in shape, and 180outof-phase with each other. Change the shunt position on header JP11 to set the switch waveforms in phase with respect to each other. To operate the ckt.s in Burst Mode, change the shunt in header JP8 to the Burst Mode position. When finished, insert shunts XJP1 and XJP2 to the OFF position(s) and disconnect the power. 6. Regulators 1 (VIN1) and 2 (VIN2) are completely separated from each other; thus, they can be powered from different individual input supplies, as can the signal input supply. Of course, all the voltage requirements still must be met: 1.5V to 20V for the PVin pins and 3.6V to 20V for the SVin pin. Warning - If the power for the demo board is carried in long leads, the input voltage at the part could “ring”, which could affect the operation of the circuit or even exceed the maximum voltage rating of the IC. To eliminate the ringing, a small tantalum capacitor (for instance, AVX part # TPSY226M035R0200) is inserted on the pads between the input power and return terminals on the bottom of the demo board. The (greater) ESR of the tantalum capacitor will dampen the (possible) ringing voltage caused by the long input leads. On a normal, typical PCB, with short traces, this capacitor is not needed. Table 1. Performance Summary (TA = 25°C) PARAMETER CONDITIONS VALUE Minimum Input Voltages 3.6V Maximum Input Voltages 20V RUN Pin = GND Shutdown RUN Pin = VIN Operating Output Voltage VOUT1 Regulation VIN1 = 3.6V to 20V, IOUT1 = 0A to 3A 1.5V ±3% (1.455V - 1.545V) 1.8V ±3% (1.746V – 1.854V) 2.5V ±3% (2.425V – 2.575V) Typical Output Ripple VOUT1 VIN1 = 12V, IOUT1 = 3A (20 MHz BW) < 30mVP–P Output Voltage VOUT2 Regulation VIN2 = 3.6V to 20V, IOUT2 = 0A to 3A 2.5V ±3% (2.425V – 2.575V) 3.3V ±3% (3.201V – 3.399V) 5V ±3% (4.85V – 5.15V) Typical Output Ripple VOUT2 VIN2 = 12V, IOUT2 = 3A (20 MHz BW) < 30mVP–P RT Pin connected to 324k RT Pin = INTVCC Channel 1: Vin = 12V, Vout1 = 1.8V, Fsw = 1 MHz Channel 2: Vin = 12V, Vout2 = 3.3V, Fsw = 1 MHz Channel 1: Vin = 12V, Vout1 = 1.8V, Fsw = 2 MHz Channel 2: Vin = 12V, Vout2 = 3.3V, Fsw = 2 MHz Phase Pin = INTVCC Phase Pin = GND 1 MHz 2 MHz Iout1 < 1.5A Iout2 < 1.25A Iout1 < 1A Iout2 < 0.75 A Out-of-Phase In Phase 3.3V ±6% Run Nominal Switching Frequencies Burst Mode Operation Output Current Thresholds Phase INTVCC 2 LTC3633AEFE-3 Figure 1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Ripple 3 LTC3633AEFE-3 Figure 3. LTC3633A-3 DC1896 Switch Operation VIN1&2 = 12V, VOUT1 = 1.8V @ IOUT1 = 3A, VOUT2 = 3.3V @ IOUT2 = 3A Forced Continuous Mode FSW = 1 MHz External Compensation: Rithx = 13k, Cithx = 220 pF Trace 1: VSW1 (10V/div) Trace 3: VOUT1 AC Voltage (20mV/div AC) Trace 2: VSW2 (10V/div) Trace 4: VOUT2 AC Voltage (20mV/div AC) 4 LTC3633AEFE-3 Figure 4. VOUT1 Load Step Response VIN1 = 12V, VOUT1 = 1.8V, 3A Load Step (0A 3A) Forced Continuous Mode FSW = 1 MHz External Compensation: Rith1 = 13k, Cith1 = 220 pF Trace 1: Output Voltage (100mV/div AC) Trace 4: Output Current (1A/div) 5 LTC3633AEFE-3 Figure 5. VOUT2 Load Step Response VIN2 = 12V, VOUT2 = 3.3V, 3A Load Step (0A 3A) Forced Continuous Mode FSW = 1 MHz External Compensation: Rith2 = 13k, Cith2 = 220 pF Trace 1: Output Voltage (200mV/div AC) Trace 4: Output Current (1A/div) 6 LTC3633AEFE-3 Figure 6. LTC3633A-3 DC1896 Efficiency 7 E2 E15 E6 E4 E1 E16 [1] + CIN6 22uF 25V 7343 22uF 25V 7343 + CIN5 [1] COUT3 22uF 6.3V 1206 5 6 CIN4 22uF 25V 1210 OPT 2.5V 1.8V CIN2 22uF 25V 1210 VIN2 1% R12 OPT VIN1 INT EXT OPT D1 3 2 1 2MHz (INT.) 1MHz JP12 ITH1 C1 0.1uF RUN1 R1 1M JP3 26 27 22 JP14 U1 LTC3633AEFE-3 14 12 15 17 16 20 23 9 3 2 1 CC2 10pF OPT INTVCC 220pF CITH2 RITH2 13K 1% THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS. LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. 6 4 JP13 ITH2 INT EXT 5 3 1 R8 11.5K 1% R6 18.7K 1% R10 26.7K 1% VOUT2 5V 3.3V 2.5V JP7 JP5 SCALE = NONE DATE: N/A SIZE GND GND TECHNOLOGY R11 10k SYNC LTC3633AEFE-3 DEMO CIRCUIT 1896A 05/03/13 12:32:05 IC NO. SHEET 1 OF 1 1 REV. 1630 McCarthy Blvd. Milpitas, CA 95035 Phone: (408)432-1900 www.linear.com Fax: (408)434-0507 LTC Confidential-For Customer Use Only E12 VO2 SELECT E14 E7 VOUT2 SVIN GND PGOOD2 TRACK2 DUAL SYNCHRONOUS STEP-DOWN REGULATOR TITLE: SCHEMATIC E13 E3 E8 E11 CSVIN1 1uF E5 COUT6 10uF 6.3V 0805 JP15 COUT4 22uF 6.3V 1206 VIN2 FCM (FORCED CONTINUOUS MODE) APP ENG. TOM G. PCB DES. MI D4 RTR4 OPT RTR2 0 CMDSH-3-TR COUT2 22uF 6.3V 1206 CSVIN 1uF BURST MODE SYNC APPROVALS JP8 MODE 3 2 1 R4 84.5K 1% D3 SVIN CMDSH-3-TR INTVCC VIN1 INTVCC OPT D2 CFFW2 10pF JP2 OFF ON TRACK SS SVIN RUN2 JP4 C2 0.1uF L2 2.2uH VISHAY IHLP-2020BZER2R2M01 RUN2 R2 1M CUSTOMER NOTICE ITH2 VFB2 VON2 SW2 SW2 BOOST2 SVIN RUN2 RPG2 100K 3 2 1 TRACK/SS2 3 RT 324K 1% 220pF CITH1 ITH1 VFB1 VON1 SW1 SW1 BOOST1 PHMODE RUN1 VIN2 CTR2 4700pF 2 INTVCC INTVCC RITH1 13K 1% 1 3 28 VIN1 1uF CVCC CVCC1 1uF INTVCC 2 1 FREQ CC1 10pF OPT 5 6 RPG1 100K VISHAY IHLP-2020BZER1R0M01 L1 1.0uH JP1 3 2 1 CFFW1 10pF OFF ON RUN1 SVIN TRACK 3 2 CTR1 4700pF [1] CIN5 AND CIN6 ARE INSERTED ON DC1896A TO DAMPEN THE (POSSIBLE) RINGING VOLTAGE DUE TO THE USE OF LONG INPUT LEADS. ON A NORMAL, TYPICAL PCB, WITH SHORT TRACES, CIN5 AND CIN6 ARE NOT NEEDED. R9 11K R7 17.4K 1% R3 34.8K 1% R5 23.2K 1% COUT1 22uF 6.3V 1206 INTVCC RPHMDE 1M INTVCC 1.5V CIN1 22uF 25V 1210 VIN1 VIN2 CIN3 22uF 25V 1210 OPT 3 4 JP6 1 2 VO1 SELECT COUT5 10uF 6.3V 0805 VOUT1 JP11 3 2 1 PHASE OFF ON RTR3 OPT RTR1 0 NOTES: UNLESS OTHERWISE SPECIFIED, V02 - V6.3 VIN2 V 02 - V 6. 3 VIN1 GND GND 3A VOUT1 PGOOD1 TRACK1 E9 SS 1 TRACK/SS1 25 24 PVIN1 PVIN1 4 PGOOD1 INTVCC SGND 10 PGND 29 RT 8 2 TRACK/SS1 21 INTVcc 13 TRACK/SS2 11 PGOOD2 18 19 PVIN2 PVIN2 MODE/SYNC 7 A3 8 E10 LTC3633AEFE-3