DEMO MANUAL DC2117A LTC3895EFE High Input Voltage Synchronous Buck Converter DESCRIPTION Demonstration circuit 2117A is a single output high volt- N-channel MOSFET gate drivers can be adjusted from age nonisolated synchronous step-down converter that 5V to 10V to enable the use of logic- or standard-level drives all N-channel MOSFET power stage. It features the MOSFETs to maximize efficiency. The EXTV pin permits CC LTC3895EFE, a high voltage step-down DC/DC controller the LTC3895 to be powered from the output of the switch- housed in a TSSOP-38 package with several pins removed ing regulator or other available source, reducing power for high voltage spacing. dissipation and improving efficiency. This DC2117A operates over an input voltage range from A mode selector allows the DC2117A to operate in forced 14V to 130V, while the LTC 3895 can operate up to 150V. continuous operation, pulse-skipping or low ripple This demo board produces a 12V output voltage with up to Burst Mode operation during light loads. Additional a 5A output current, and is configured with a sense resistor features include a power good output signal, a PLLIN, for over current protection and has optional DCR sensing. PHASEMD and CLKOUT for multiphase operation. To prevent high on-chip power dissipation in high input The LTC3895 data sheet gives a complete description of voltage applications, the LTC3895 includes an NDRV pin the part, operation and application information and must which drives the gate of an optional external N-channel be read in conjunction with this demo board manual. MOSFET acting as a low dropout linear regulator to supply Design files for this circuit board are available at IC power and is an option on this board. DEMO MANUAL DC2117A QUICK START PROCEDURE Demonstration circuit DC2117A is easy to set up to evalu- 2. With power off, connect the input power supply to V IN ate the performance of the LTC3895EFE. Refer to Figure 1 and GND. for proper measurement equipment setup and follow the 3. Turn on the power at the input. procedure below: NOTE. Make sure that the input voltage is higher than NOTE. When measuring the input or output voltage ripple, 14V and does not exceed 130V. care must be taken to avoid a long ground lead on the 4. Check the output voltage. The output voltage should oscilloscope probe. Measure the input or output voltage be between 11.76V and 12.24V. ripple by touching the probe tip directly across the V IN or V and GND terminals or directly across relevant OUT Once the proper output voltage is established, adjust capacitor. See Figure 2 for proper scope probe technique. the load within the operating range and observe the output voltage regulation, output voltage ripple, 1. Place jumpers in the following positions: efficiency and other parameters. JP1 ON NOTE. If there is no output, temporarily disconnect the JP4 FCM load to make sure that the load is not set too high. JP5 ON JP8 OFF Figure 1. Proper Measurement Equipment Setup dc2117afa 2