DEMO MANUAL DC2299A LTC3890, 60V, LOW IQ DUAL OUTPUT HIGH VOLTAGE STEP-DOWN CONVERTER DESCRIPTION Demonstration circuit 2299A is a high input voltage, high frequency of 200kHz, but can be adjusted to frequencies efficiency synchronous dual output buck converter fea- as high as 900kHz. turing the LTC 3890EGN. The DC2299A has a wide input The DC2299A is designed to support multiple footprints voltage range of 6V to 60V. The output voltages are set to of input/output capacitors and inductors to accommodate 5V and 12V, however, the output voltage can go as high a wide variety of applications. The LTC3890 data sheet as 24V, with certain modifications. This demo board is gives a complete description of this controller along with capable of delivering up to 8A from the 5V output and up operation and application information, and must be read to 5A from the 12V output. in conjunction with this demo board manual. The DC2299A supports three operation modes: fixed Table 1. DC2299A Variants frequency modulation, pulse-skipping and BurstMode DC2299A VARIANTS IC PART NUMBER PART MARKING operation. Fixed frequency operation maximizes the output 2299A-A LTC3890EGN-3 LTC3890GN-3 current, reduces output voltage ripple, and yields a low 2299A-B LTC3890EGN-1 LTC3890GN-1 noise switching spectrum. Burst Mode operation employs *See data sheet Table 1 for differences between the parts in the a variable frequency switching algorithm that minimizes the LTC3890family. no-load input quiescent current and improves efficiency at light loads. Design files for this circuit board are available at DEMO MANUAL DC2299A QUICK START PROCEDURE 2. Turn on V of the circuit by inserting the shunt in OUT1 Demonstration circuit 2299A is easy to set up to evaluate header JP3 (RUN1) into the ON position. The output the performance of the LTC3890. For proper measurement voltage should be regulating. Measure V it should OUT1 equipment configuration, set up the circuit according to measure 5.0V 2% (Do not apply more than the rated the diagram in Figure 1. Before proceeding to test, insert maximum voltage of 60V to the board or the part may shunts into JP3 and JP2 (RUN1, 2) into the OFF position, be damaged). Vary the V load, which should not OUT1 which connects the RUN pins to ground (GND), and thus, exceed 8A. Vary the input voltage from 6V to 55V, the shuts down the outputs. Set jumper JP1 (MODE) into V it should measure 5.0V 2%. OUT FCM(Forced Counties Mode) position. 3. Turn on V of the circuit by inserting the shunt in OUT2 NOTE: When measuring the input or output voltage header JP2 (RUN2) into the ON position. The output ripple, care must be taken to avoid a long ground lead voltage should be regulating. Measure V it should OUT2 on the oscilloscope probe. Measure the input or output measure12.0V 2% (Do not apply more than the rated voltage ripple by touching the probe tip directly across maximum voltage of 60V to the board or the part may the V or V and GND terminals. See Figure 2 for IN OUT be damaged). Vary the V load, which should not OUT2 proper scope probe technique. exceed 5A. Vary the input voltage from 16V to 55V, the 1. With the DC2299A set up according to the proper V it should measure 12.0V 2%. OUT measurement and equipment in Figure 1, apply 20V 4. Set output current to zero and move jumper JP1 (MODE) at V . Measure V it should read 0V. If desired, IN OUT into Burst Mode position and measure V and V . OUT1 OUT2 one can measure the shutdown supply current at this point. The supply current will be approximately 50A, 5. Set output current to zero and move jumper JP1 (MODE) or less, in shutdown. into PLS SKIP position and measure V and V . OUT1 OUT2 Figure 1. Proper Measurement Equipment Setup dc2299afa 2