DC1757A Analog Devices

DEMO MANUAL DC1757A LTC3789EGN High Efficiency 12V/12A Buck-Boost Converter DESCRIPTION Demonstration circuit 1757A is a high efficiency syn- The light load operation mode of the converter is de- chronous buck-boost DC/DC converter with a 6V to 36V termined with the MODE/PLLIN pin. Use JP2 jumper to input voltage range. It can supply a 12A maximum load select pulse-skipping mode or forced continuous mode current with a 12V output. The demo board features the (CCM) operation. The switching frequency is pre-set LTC 3789EGN controller. The constant frequency current at about 200kHz. The converter can also be externally mode architecture allows a phase-lockable frequency of up synchronized to an external clock through the MODE/ to 600kHz, while an optional output current feedback loop PLLIN pin (PLLIN terminal on the board). To shut down provides support for applications such as battery charging. the converter, force the RUN pin below 1.2V (JP1: OFF). With a wide input range, wide output range and seamless The power good output (PGOOD terminal) is low when the transfers between operation modes, the LTC3789 is ideal output voltage is outside of the 10% regulation window. for automotive, telecom, distributed DC power systems Design files for this circuit board are available at and battery-powered applications. DEMO MANUAL DC1757A QUICK START PROCEDURE Note: When measuring the output or input voltage rip- Additional Notes: ple, do not use the long ground lead on the oscilloscope 1. On DC1757 board, two Coilcraft XAL1010 inductors are probe. See Figure 2 for the proper scope probe technique. used in series instead of one larger inductor, for optimal Short, stiff leads need to be soldered to the (+) and () size and performance. You may use a single inductor, terminals of an output capacitor. The probes ground ring such as Coilcraft SER2915L-332KL, if that is preferred. needs to touch the () lead and the probe tip needs to 2. Usually, the worst case efficiency at full load is at 6V . touch the (+) lead. IN The board can deliver more output power at higher V . IN 3. R2 is needed for additional/constant output current limit only. Figure 1. Proper Measurement Equipment Setup + C OUT V GND OUT Figure 2. Measuring Output Voltage Ripple dc1757af 2