DC2110A: 5V @ 1A, 6.5 ~ 100V in, Buck

Demonstration circuit 2110A is a monolithic step-down converter featuring LT®8631. The demo board is designed for 5V output from a 6.5V to 100V input at 400kHz switching frequency. The wide input range makes it suitable for regulating power from a wide variety of sources, including automotive, industrial systems and telecom supplies. The LT8631 is a compact, high efficiency synchronous monolithic step-down switching regulator. The power switch, compensation and other necessary circuits are inside of the LT8631 to minimize external components and simplify design.

The LT8631 switching frequency can be programmed either via oscillator resistor or external clock over a 100kHz to 1MHz range. The SYNC pin on the demo board is grounded (JP1 at Burst Mode® position) by default for low ripple Burst Mode operation. To synchronize to an external clock, move JP1 to SYNC and apply the external clock to the SYNC turret. If the pulse-skipping operation is required, move JP1 to fixed frequency position.

Figure 1 shows the efficiency of the circuit at 12V input at the Burst Mode selection.The demo board has an EMI filter installed.

The EMI performance of the board (with EMI filter) is shown in Figure 2. The red line in Figure 2 is CISPR25 Class 5 peak limit. The figure shows that the circuit passes the test with a wide margin. To achieve EMI/EMC performance as shown in Figure 2, the input EMI filter is required and the input voltage should be applied at VEMI turret pin, not VIN.

The LT8631 data sheet gives a complete description of the part, operation and application information. The data sheet must be read in conjunction with this demo manual for demo circuit 2110A. The LT8631 is assembled in a 20-lead TSSOP packages. Proper board layout is essential for maximum thermal and electrical performance. See the data sheet sections for details.