Demonstration circuit 3020A is a 42V, 5A (7A Peak) synchronous step-down Silent Switcher® with spread spectrum frequency modulation featuring the LT8637. The demo board is designed for 5V output from a 5.8V to 42V input. The wide input range allows a variety of input sources, such as automotive batteries and industrial supplies. The LT8637 is a compact, low emission, high efficiency, and high frequency synchronous monolithic stepdown switching regulator. The LT8637 is the same as the LT8636, except it has a VC pin for external compensation. This allows the customer to optimize the loop response, or to parallel multiple regulators for higher current applications. The proprietary Silent Switcher architecture minimizes electromagnetic emissions with simplified filter and reduced layout sensitivity. Selectable spread spectrum mode further improves EMI performance, making it perfect solution to the noise sensitive applications. The regulator’s ultralow 2.5μA quiescent current—with the output in full regulation—enables applications requiring highest efficiency at very light load currents, such as automotive and battery powered portable instruments.
Peak current mode control with minimum on-time of as small as 30ns allows high step-down conversion even at high frequency. The LT8637 switching frequency can be programmed either via oscillator resistor or external clock over a 200kHz to 3MHz range. The default frequency of demo circuit 3020A is 2MHz.
The SYNC/MODE pin on the demo board DC3020A is grounded (JP1 at BURST position) by default for low ripple Burst Mode® operation. To synchronize to an external clock, move the Jump JP1 to SYNC/FCM and apply the external clock to the SYNC terminal ON THE 3020A. In sync mode, the part runs in forced continuous mode. Without external clock applied, the SYNC/MODE pin is floating, and the part runs in forced continuous mode. This mode offers fast transient response and full frequency operation over a wide load range. Alternatively, move the Jump JP1 to the SPREAD-SPECTRUM, and the SYNC/MODE is tied to INTVCC, the part runs in forced continuous mode with spread spectrum function enabled.
The LT8637 data sheet gives a complete description of the part, operation and application information. The data sheet must be read in conjunction with the demo manual for demo circuit 3020A. The layout recommendations for low EMI operation and best thermal performance are available in the data sheet section Low EMI PCB Layout and Thermal Considerations and Peak Output Current. Contact ADI applications engineer for support.
