DEMO MANUAL DC1807A LTC3869EUFD Dual, 2-Phase Synchronous Step-Down DC/DC Controllers DESCRIPTION Demonstration circuit 1807A is a dual output, dual phase Two versions of the board are available. DC1807A-A has synchronous buck converter featuring the LTC3869EUFD. an on-board sense resistor for current feedback, while The demo board uses a high density, two sided drop-in the DC1807A-B is configured with a DCR sense circuit layout. The power components, excluding the bulk out- that allows the converter to use the inductors DCR as the put and input capacitors, fit within a 1.35 0.75 area sense element instead of the on-board sense resistors to on the top layer. The control circuit resides in a 0.60 save cost and board space and improves efficiency. 0.75 area on the bottom layer. The package style for the The input voltage range is 4.5V to 14V, output voltages LTC3869EUFD is a 4mm 5mm 28-lead QFN with an and currents are 1.5V/15A and 1.2V/15A. The LTC3869 exposed ground pad. datasheet gives a complete description of the part, opera- The main features of the board include an internal 5V linear tion and application information. The datasheet must be regulator for bias, RUN pins for each output, an EXTV read in conjunction with this demo manual for DC1807A. CC pin and a PGOOD signal. The board can be configured Design files for this circuit board are available at for either CCM (original setting), Burst Mode operation, DEMO MANUAL DC1807A QUICK START PROCEDURE Demonstration circuit 1807A is easy to set up to evaluate 3. Turn on the power at the input. the performance of the LTC3869EUFD. Refer to Figure 1 NOTE. Make sure that the input voltage does not exceed for proper measurement equipment setup and follow the 28V. procedure below: 4. Check for the proper output voltages. NOTE. When measuring the input or output voltage ripple, V = 1.470V to 1.530V, care must be taken to avoid a long ground lead on the OUT1 oscilloscope probe. Measure the input or output voltage V = 1.176V to 1.224V, OUT2 ripple by touching the probe tip directly across the V or IN NOTE. If there is no output, temporarily disconnect the V and GND terminals. See Figure 2 for proper scope OUT load to make sure that the load is not set too high. probe technique. 5. Once the proper output voltages are established, adjust 1. Make sure jumpers are in the following positions: the loads within the operating range and observe the JUMPER POSITION output voltage regulation, ripple voltage, efficiency and JP1 ON other parameters. JP2 ON 6. Different operating modes can be evaluated by chang- JP3 CCM ing position of jumper JP3. 2. With power off, connect the input power supply to V IN and GND. Connect active loads to outputs. V A V OUT1 Load A POWER V SUPPLY A V OUT2 Load V Figure 1. Proper Measurement Equipment Setup dc1807af 2