Analog Devices LT8645S | Demoboard DC2468A

Description

Demonstration circuit 2468A is a 65V, 8A micropower synchronousstep-down second generation Silent Switcher®with spread spectrum frequency modulation featuring theLT8645S. The demo board is designed for 5V output froma 5.6V to 65V input. The wide input range allows a varietyof input sources, such as automotive batteries and industrialsupplies. The LT8645S is a compact, ultralow emission,high efficiency, and high speed synchronous monolithicstep-down switching regulator. The integrated bypasscapacitors optimize all the fast current loops and make iteasier to minimize EMI/EMC emissions by reducing layoutsensitivity. Selectable spread spectrum mode can furtherimprove EMI/EMC performance. Ultralow quiescent currentin Burst Mode® operation achieves high efficiency atvery light loads. Fast minimum on-time of 40ns enableshigh VIN to low VOUT conversion at high frequency.The LT8645S switching frequency can be programmedeither via oscillator resistor or external clock over a200kHz to 2.2MHz range. The default frequency of democircuit 2468A is 2MHz. The SYNC pin on the demo boardis grounded (JP1 at BURST position) by default for lowripple Burst Mode operation. To synchronize to an externalclock, move JP1 to SYNC and apply the external clockto the SYNC terminal. Spread spectrum mode and pulseskipping mode can be selected respectively by movingJP1 shunt. Figure 1 shows the efficiency of the circuit at12V input and 24V input in Burst Mode operation (inputfrom VIN terminal to bypass the EMI filter). Figure 2 showsthe LT8645S temperature rising on DC2468A demo boardunder different load conditions. The rated maximum load

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