DEMO MANUAL DC2112A LTC3649 60V, Low IQ Monolithic High Efficiency Step-Down Regulator DESCRIPTION Demonstration circuit 2112A is a high input voltage, high The DC2112A consumes less than 15A of quiescent cur- efficiency synchronous monolithic buck converter featur- rent during shutdown and it consumes less than 440A ing the LTC3649 in a 28-lead UFD package. The DC2112A at no load conditions in Burst Mode of operation. The has wide input voltage range from 3.1V up to 60V. The DC2112A has a standard operating frequency of 500kHz, output voltage of the DC2112A can be set as to 3.3V or but can be adjusted in a range between 300kHz and as high 5V. However, the USER SELECT option of DC2112A as 3MHz. DC2112A is a monolithic step-down converter, allows output voltage to be as high as input voltage minus LTC3649 integrates top and bottom N-channel MOS- 0.5V, with certain modifications. DC2112A is capable of FETs, significantly reducing circuit footprint. DC2112A delivering up to 4A of output current. DC2112A supports was designed to support multiple footprints of input/out- three operation modes: Fixed-Frequency modulation and put capacitors and inductor to accommodate variety of Burst Mode, user can synchronize it with an external clock applications. The data sheet of LTC3649 gives a complete also. Fixed-Frequency mode of operation maximizes the description functionality of this regulator also contains output current, reduces output voltage ripple, and yields operation and application information and must be read in a low noise switching spectrum. Burst Mode employs a conjunction with this demo board manual for DC2112A. variable frequency switching algorithm that minimizes the Design files for this circuit board are available at no-load input quiescent current and improves efficiency DEMO MANUAL DC2112A QUICK START PROCEDURE Demonstration circuit 2112A is easy to set up to evaluate voltage should be regulating. Measure V it should OUT the performance of the LTC3649. For proper measurement measure 5.0V 2% (Do not apply more than the rated equipment configuration, set up the circuit according to the maximum voltage of 60V to the board or the part may diagram in Figure 1. Before proceeding to test, insert shunt be damaged). Vary the V load, which should not OUT into JP2 (RUN) into OFF position, which connects the RUN exceed 4A. Vary the input voltage from 6V to 55V, the pin to ground (GND), and thus, shutdown the output. Set V it should measure 5.0V 2%. OUT jumper JP1 (MODE) into FCC (Forced Counties Conduction 3. Set JP2 (RUN) into OFF and then jumper JP3 (V ) OUT Mode) position. Set jumper JP3 (V ) into 5.0V position. OUT into 3.3V position. NOTE: When measuring the input or output voltage ripple, 4. Turn on V of the circuit by inserting the shunt in OUT2 care must be taken to avoid a long ground lead on the header JP2 (RUN) into the ON position. The output oscilloscope probe. Measure the input or output voltage voltage should be regulating. Measure V it should OUT ripple by touching the probe tip directly across the V or IN measure 3.3V 2% (Do not apply more than the rated V and GND terminals. See Figure 2 for proper scope OUT maximum voltage of 60V to the board or the part may probe technique. be damaged). Vary the V load, which should not OUT 1. With the DC2112A set up according to the proper mea- exceed 4A. Vary the input voltage from 16- 55V, the surement and equipment in Figure 1, apply 12V at V . V it should measure 3.3V 2% IN OUT Measure V it should read 0V. If desired, one can OUT 5. Set output current to zero and move jumper JP1 (MODE) measure the shutdown supply current at this point. The into BURST position and measure V for 3.3V. OUT supply current will be approximately 14A, or less, in 6. Set output current to zero and move jumper JP1 (MODE) shutdown. into BURST position and measure V for 5.0V. OUT 2. Turn on V of the circuit by inserting the shunt in OUT header JP2 (RUN) into the ON position. The output + LOAD + + LOAD + + + DC2112A F01 Figure 1. Proper Measurement Equipment Setup dc2112af 2