QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 392 HIGH EFFICIENCY DUAL REGULATOR LTC1628 or LTC3728 DESCRIPTION Demonstration circuit 392 is a dual output, step-down, synchronous buck converter featuring either the 150kHz to 300kHz LTC1628EUH controller (DC392A-A), the 250kHz to 550kHz LTC3728EUH (DC392A-B) or 250kHz to 550kHz LTC3728LUH (DC392A-C). All three ICs come in a 5mmx5mm QFN package with an exposed pad for low thermal impedance. The input voltage is from 7V up to 24V. Output 1 is 5V with loads up to 4A and output 2 is 3.3V with loads up to 5A. Design files for this circuit board are available. Call the LTC factory. Table 1. Performance Summary PARAMETER CONDITION VALUE Minimum Input Voltage 7V Maximum Input Voltage 24V VOUT1 VIN = 7V to 24V, IOUT1 = 0A to 4A 5V 1% VOUT2 VIN = 7V to 24V, IOUT1 = 0A to 5A 3.3V 1% Switching Frequency (LTC1628) Switching Frequency (LTC3728) Jumper selectable Jumper selectable 150kHz-300kHz 250kHz-550kHz QUICK START PROCEDURE Demonstration circuit 392 is easy to set up to evaluate the performance of the LTC1628 or LTC3728. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below: NOTE: The input voltage range should be 7V-24V in- stead of 5V-24V as shown on the board. NOTE: When measuring the input or output voltage rip- ple, 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 Figure 2 for proper scope probe technique. 1. With the power off, place the jumpers as shown in Figure 1. NOTE: The STBY and FLTCPL jumpers apply only to demo circuit 392A-A (featuring the LTC1628). These jumpers are not used for the DC392A-B or DC392A-C which feature the LTC3728. 3. Set Vin to 12V (recommended). The rated input voltage range is from 7V to 24V. 4. Remove the RUN1 jumper to switch on the Vout1 channel. The nominal output voltage of Vout1 should be 5V 0.1V. Increase load current on Vout1 to 4A. At 12V input voltage, the input current should be less than 2A. Slowly increase the input voltage to 24V. At 24V input, the input current should be less than 1.1A. 5. Decrease the load current of Vout1 to 0A. Reduce the input voltage to 12V. 6. Remove the RUN2 jumper to switch on the Vout2 channel. The output voltage of Vout2 should be 3.3V 0.05V. 7. Increase load current on Vout2 to 5A. At 12V input voltage, the input current should be less than 1.8A. Slowly increase the input voltage to 24V. At 24V input, the input current should be less than 1.0A. 2. Connect the loads at Vout1 and Vout2. The loads can be up to 4A for Vout1 and 5A for Vout2. Pre-set the loads to 0A. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 392 HIGH EFFICIENCY DUAL REGULATOR + + + + - + - - LOAD - - + LOAD - - - + + + - Figure 1. Proper Measurement Equipment Setup GND VIN Figure 2. Scope Probe Placement for Measuring Input or Output Ripple 2 E7 1 1 1 1 1 1 LTC3728EUH LTC3728LUH 392A-B 392A-C 3 LTC1628EUH 0 3 3 3 3 3 392A-A 1 0 0 0 0 0 U1 C24 0.01uF JP6 RUN2 1 JP5 FCB JP4 STBY 1 JP3 FSET 1 JP2 FLTCPL 1 JP1 RUN1 1 ASSEMBLY 3.3V LDO E8 5V LDO R16 1M R12 1M R9 1M 2 2 2 2 2 2 C15 0.01uF L1 Table: C18 0.01uF C21 0.01uF IHLP-2525CZ-01-2.2uH IHLP-2525CZ-01-2.2uH CDEP105-4R3MC-88 R7 1M (Opt.) R4 1M 2 C19 180pF R14 20K 1% R11 4.75K 1% R10 8.06K 1% L2 Dual Output 1 R13 63.4K 1% C14 1000pF C16 100pF C6 1500pF C9 100pF C1 0.1uF C2 180pF R5 105 K 1% 2 3 IHLP-2525CZ-01-2.2uH TG1 0.006 ohm C10 1uF 13 14 15 17 18 19 20 21 22 C17 0.1uF 1,2 2,3 1,2 1,2 1,2 1,2 JP1 JP2 JP3 JP4 JP5 JP6 JP8 2 Q2B FDS6982S 4 C7 0.1uF R8 10 4 Q1B FDS6982S Short Pin 1,2 Short Pin 1,2 Short Pin 2,3 Short Pin 2,3 Dual Output D2 CMDSH-3 2 D3 CMDSH-3 Single Output Jumpers Select Short Pin Ref. 1 + C8 4.7uF 10V 1 24 23 C5 0.1uF 25 Jumpers Select RUN/SS2 TG2 SW2 BOOST2 BG2 PGND INTVCC EXTVCC BG1 VIN BOOST1 SW1 26 JP7 R17 10 R18 10 SENSE2+ SENSE2- VOSENSE2 ITH2 3.3VOUT SGND ITH1 FCB STBYMD FREQSET VOSENSE1 SENSE1- SENSE1+ FLTCPL 27 0.006 ohm 12 11 9 8 7 6 5 4 3 2 1 31 RUN/SS1 U1 See Table Ref. R3 C20 1000pF C3 1000pF 30 28 0.008 ohm Single Output JP8 ITH IHLP-2525CZ-01-2.2uH CDEP105-4R3MC-88 C23 0.1uF R6 20K 1% JP7 VOSENSE R1 10 R2 10 32 NC NC 10 29 NC NC 16 Single Output 3 3 2 2 Q1A FDS6982S 5 6 3 5 6 Q2A FDS6982S L1 See Table L2 See Table D4 MBRM140T3 (Opt.) D1 MBRM140T3 (Opt.) 7 8 1 1 7 8 Dual Output 1 R15 0.008 C12 10uF 35V R3 See Table C13 10uF 35V + C22 180uF,4V SP + C11 33uF,35V Sanyo + C4 150uF,6V SP C32 1uF C25 1uF E6 Gnd 3.3V @ 5A E5 Vout2+ E4 Gnd 5V to 2 4V E3 Vin E2 Gnd 5V @ 4A E1 Vout1+ QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 392 HIGH EFFICIENCY DUAL REGULATOR 3