DC392A-C Analog Devices

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 392 HIGH EFFICIENCY DUAL REGULATOR LTC1628 or LTC3728 DESCRIPTION Demonstration circuit 392 is a dual output, step-down, low thermal impedance. The input voltage is from 7V up synchronous buck converter featuring either the 150kHz to 24V. Output 1 is 5V with loads up to 4A and output 2 to 300kHz LTC1628EUH controller (DC392A-A), the is 3.3V with loads up to 5A. 250kHz to 550kHz LTC3728EUH (DC392A-B) or 250kHz Design files for this circuit board are available. Call to 550kHz LTC3728LUH (DC392A-C). All three ICs come the LTC factory. in a 5mm5mm QFN package with an exposed pad for Table 1. Performance Summary PARAMETER CONDITION VALUE Minimum Input Voltage 7V Maximum Input Voltage 24V V V = 7V to 24V, I = 0A to 4A 5V 1% OUT1 IN OUT1 V V = 7V to 24V, I = 0A to 5A 3.3V 1% OUT2 IN OUT1 Switching Frequency (LTC1628) Jumper selectable 150kHz300kHz Switching Frequency (LTC3728) Jumper selectable 250kHz550kHz QUICK START PROCEDURE Demonstration circuit 392 is easy to set up to evaluate 3. Set Vin to 12V (recommended). The rated input the performance of the LTC1628 or LTC3728. Refer to voltage range is from 7V to 24V. Figure 1 for proper measurement equipment setup and 4. Remove the RUN1 jumper to switch on the Vout1 follow the procedure below: channel. The nominal output voltage of Vout1 NOTE: The input voltage range should be 7V24V in- should be 5V 0.1V. stead of 5V-24V as shown on the board. Increase load current on Vout1 to 4A. At 12V input NOTE: When measuring the input or output voltage rip- voltage, the input current should be less than 2A. ple, care must be taken to avoid a long ground lead on Slowly increase the input voltage to 24V. At 24V in- the oscilloscope probe. Measure the input or output put, the input current should be less than 1.1A. voltage ripple by touching the probe tip directly across 5. Decrease the load current of Vout1 to 0A. Reduce the Vin or Vout and GND terminals. See Figure 2 for the input voltage to 12V. proper scope probe technique. 6. Remove the RUN2 jumper to switch on the Vout2 1. With the power off, place the jumpers as shown in channel. The output voltage of Vout2 should be Figure 1. 3.3V 0.05V. NOTE: The STBY and FLTCPL jumpers apply only to 7. Increase load current on Vout2 to 5A. At 12V input demo circuit 392A-A (featuring the LTC1628). These voltage, the input current should be less than 1.8A. jumpers are not used for the DC392A-B or Slowly increase the input voltage to 24V. At 24V in- DC392A-C which feature the LTC3728. put, 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. 1GND VIN QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 392 HIGH EFFICIENCY DUAL REGULATOR + LOAD LOAD Figure 1. Proper Measurement Equipment Setup Figure 2. Scope Probe Placement for Measuring Input or Output Ripple 2 + + + + + + + +