DEMO MANUAL DC1928A LTC3867EUF High Efficiency Synchronous Buck Converter DESCRIPTION Demonstration circuit 1928A is a single output synchronous optional temperature compensated DCR sense circuit, buck converter featuring the LTC 3867EUF in a 24-lead and selectable continuous, pulse-skipping or Burst Mode 4mm x 4mm QFN package. operation. Synchronization to an external clock is also possible. The DC1928A is configured with a sense resistor. Inductor DCR sensing circuit is optional. Using the inductors DCR The input voltage range is from 18V to 36V. The LTC3867 as the sense element instead of the onboard sense resistor data sheet gives a complete description of the part, opera- saves cost, board space while improving efficiency. Using tion and application information and must be read in con- a sense resistor provides more accurate current limit. junction with this demo manual for DC1928A. The board has a lot of features including an internal 5V Design files for this circuit board are available at linear regulator for bias, output voltage remote-sense, DEMO MANUAL DC1928A QUICK START PROCEDURE Demonstration circuit DC1928A is easy to set up to evalu- Once the proper output voltage is established, adjust the ate the performance of the LTC3867EUF. Please refer to load within the operating range and observe the output Figure 2 for proper measurement equipment setup and voltage regulation, output voltage ripple, efficiency and follow the procedure below: other parameters. 1. Place jumpers in the following positions for a typical Note: When measuring the input or output voltage ripple, application: care must be taken to avoid a long ground lead on the oscilloscope probe. Measure the input or output voltage JP2: On ripple by touching the probe tip directly across the VIN or JP3: CCM VOUT and GND terminals. See Figure 2 for proper scope probe technique. 2. With power off, connect the input power supply, load and meters as shown in Figure 1. Preset the load to 0A 5. Change JP3 jumper position to select different operation and V supply to 24V. IN modes. Set jumper to CCM, BURST or P.S. position toe set forced continuous conduction, burst or pulse- 3. Turn on the power supply at the input. skipping mode respectively. For synchronizing to an Note: Make sure that the input voltage does not exceed 36V. external clock source, set the jumper to BURST position and apply the clock signal to MODE/PLLIN turret. 4. Check the output voltage. The output voltage should be between 11.76V and 12.24V. Figure 1. Test Setup of DC1928A dc1928af 2