DEMO CIRCUIT 1347B LTC3633 QUICK START GUIDE DESCRIPTION LTC3633 DUAL CHANNEL 3A15V MONOLITHIC SYNCHRONOUS STEP-DOWN REGULATOR BOARD Demonstration circuit DC1347 is a dual output regulator consisting of two constant-frequency step-down converters, based on the LTC3633 monolithic dual channel synchronous buck regulator. The DC1347 has an input voltage range of 3.6V to 15V, with each regulator capable of delivering up to 3A of output current. The DC1347 can operate in either Burst Mode or forced continuous mode. In shutdown, the DC1347 can run off of less than 15 uA total. The DC1347 is a very efficient circuit: over 90% for either circuit. The LTC3633 comes in a 28 Pin QFN or leaded package, which each having 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 DC1347 demo board an ideal circuit for use industrial or distributed power applications. Gerber files for this circuit are available. Call the LTC Factory. QUICK START PROCEDURE The DC1347 is easy to set up to evaluate the performance of the LTC3633. 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. Please follow the procedure outlined below for proper operation. 1. Connect the input power supply to the Vin and GND terminals. Connect the loads between the Vout and GND terminals. Refer to figure 1 for the proper measurement equipment setup. 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 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: 1.2V, 1.5V, or 1.8V, and a shunt into the Vout2 voltage option of choice: 2.5V (header JP15), 3.3V (header JP5), or 5V (header JP7). 2. Apply 5.5V at Vin. 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 100 uA in shutdown. 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 voltage from 5.8V (the min. Vin is dependent on Vout) to 15V, and the load currents from 0 to 3A. Both output voltages should be within +/- 4% tolerance. 1 LTC3633 5. Set the load current of both outputs to 3A and the input voltage to 15V, 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 realize 2 MHz operation, change the shunt position on header JP14. In all cases, both switch node waveforms should be rectangular in shape, and 180°out-of-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. 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 will dampen the (possible) ringing voltage due to the use of 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 Voltage 3.6V Maximum Input Voltage 15V Run RUN Pin = GND Shutdown RUN Pin = VIN Operating 1.2V ±4% (1.152V – 1.248V) Output Voltage VOUT1 VIN = 3.6V to 15V, IOUT1 = 0A to 3A 1.5V ±4% (1.44V - 1.56V) 1.8V ±4% (1.728V – 1.872V) Typical Output Ripple VOUT1 Output Regulation VOUT1 VIN = 12V, IOUT1 = 3A (20 MHz BW) < 30mVP–P Line ±1% Load ±1% 2.5V ±4% (2.4V – 2.6V) 3.3V ±4% (3.168V – 3.432V) 5V ±4% (4.8V – 5.2V) Output Voltage VOUT2 VIN = 3.6V to 15V, IOUT2 = 0A to 3A Typical Output Ripple VOUT2 VIN = 12V, IOUT2 = 3A (20 MHz BW) < 30mVP–P Line ±1% Load 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% 1 MHz 2 MHz Iout1 = 1.3A Iout2 = 850 mA Iout1 = 800 mA Iout2 = 500 mA Out-of-Phase In Phase 3.3V 2.5V Output Regulation VOUT2 Nominal Switching Frequencies Burst Mode Operation Phase INTVCC V2P5 2 LTC3633 Figure 1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Ripple 3 LTC3633 Figure 3. VOUT1 Load Step Response VIN = 12V, VOUT1 = 1.8V, 3A Load Step (0.1A <-> 3A) Forced Continuous Mode FSW = 2 MHz External Compensation: Rith = 13k, Cith = 220 pF Trace 3: Output Voltage (100mV/div AC) Trace 4: Output Current (1A/div) 4 LTC3633 Figure 4. VOUT2 Load Step Response VIN = 12V, VOUT2 = 3.3V, 3A Load Step (0.1A <-> 3A) Forced Continuous Mode FSW = 2 MHz External Compensation: Rith = 13k, Cith = 220 pF Trace 3: Output Voltage (100mV/div AC) Trace 4: Output Current (1A/div) 5 LTC3633 95 90 Vo2 = 3.3V 85 Efficiency (%) Vo1 = 1.8V 80 75 70 Vin = 12V fsw = 1 MHz Burst Mode L1 =1 uH L2 = 2.2 uH 2020BZ Vishay 65 60 0.00E+00 5.00E-01 1.00E+00 1.50E+00 2.00E+00 Load Current (A) Figure 5. LTC3633 DC1347 Efficiency 6 2.50E+00 3.00E+00 E2 E15 E6 E4 E1 E16 [1] + CIN6 22uF 35V 7343 [1] + CIN5 22uF 35V 7343 CIN4 47uF 16V OPT 1210 5 6 CIN3 47uF 16V OPT 1210 3 4 VIN VIN JP6 1 2 1.8V 1.5V CIN2 47uF 16V 1210 INTVCC 1M D1 INT EXT 10pF CFFW1 OPT 2MHz (INT.) 1MHz JP12 3 2 1 L1 1.0uH 3 3 0.1uF CBST1 R1 1M JP3 JP14 2. ALL RESISTOR AND CAPACITOR CASE SIZE ARE 0402. VIN 11 9 12 14 13 17 18 LT C3633EUFD U1 ITH2 FB2 VON2 SW2 SW2 BOOST2 V2P5 RUN2 6 RPG2 100K R2 2.2uH VIN 3 2 1 TRACK SS CC2 10pF OPT INTVCC 220pF CITH2 RITH2 13K 1% 6 D2 3 2 1 JP8 JP13 ITH2 10pF R4 84.5K 1% INTVCC 5 3 1 R8 11.5K 1% R6 18.7K 1% 5V 3.3V 2.5V COUT4 22uF 6.3V 1206 VOUT2 RTR4 OPT JP7 JP5 CLDO 1uF OPT R11 10k COUT6 10uF 6.3V 0805 JP15 RTR2 0 FCM (FORCED CONTINUOUS MODE) SY NC COUT2 22uF 6.3V 1206 C2P5 1uF R10 26.7K 1% BURST MODE INTVCC INT EXT OFF ON CFFW2 OPT JP2 RUN2 MODE VISHAY IHLP-2020BZER2R2M01 0.1uF L2 JP4 CBST2 1M 3 2 1 TRACK/SS2 4 RT 324K 1% VIN CTR2 4700pF 2 220pF CITH1 ITH1 FB1 VON1 SW1 SW1 BOOST1 PHMODE RUN1 1uF 1uF CVCC CVCC1 3 INTVCC INTVCC RITH1 13K 1% 26 28 25 23 24 20 2 3 RPG1 100K CTR1 4700pF 27 2 1 FREQ CC1 10pF OPT VISHAY IHLP-2020BZER1R0M01 JP1 ITH1 OFF 2 VIN TRACK [1] CIN5 AND CIN6 ARE INSERTED ON DC1347 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 14.7K 1% R7 19.6K 1% R3 29.4K 1% R5 29.4K 1% COUT1 22uF 6.3V 1206 1.2V CIN1 47uF 16V 1210 VOLTAGE SELECT COUT5 10uF 6.3V 0805 JP11 3 2 1 ON 1 RPHMDE RUN1 INTVCC PHASE COUT3 22uF 6.3V 1206 OFF ON RTR3 OPT VOUT1 RTR1 0 NOTES: UNLESS OTHERWISE SPECIFIED, V51 - V6.3 VIN2 V51 - V6.3 VIN1 GND GND 3A VOUT1 PGOOD1 TRACK1 E9 2 1 TRACK/SS1 SS 1 PGOOD1 21 22 PVIN1 PVIN1 RT 5 INTVCC INTVcc 19 GND 7 TRACK/SS1 E10 TRACK/SS2 10 PGND 29 8 PGOOD2 15 16 PVIN2 PVIN2 MODE/SYNC 4 E12 E14 E7 E5 E13 E3 E8 E11 VOUT2 V2P5 GND PGOOD2 TRACK2 SYNC GND GND A3 INTVCC LTC3633 7