Demonstration circuit 2833A is a 100V monolithic DC/DC step-down regulator featuring the LTC7103-1. The demo board is designed for a 5V/2.3A output from a 5V to 100V input operation at a 400kHz switching frequency. The wide input range makes it suitable for automotive, industrial, medical instrument, and telecom applications. This buck regulator has a peak efficiency of 93.5% at 12VIN, 88.3% at 48VIN and 81.5% at 100VIN (see Figure 3 in the demo manual).
The LTC7103-1 is a compact, high efficiency synchronous monolithic step-down switching regulator with fast current programming. The power switches, compensation network and other necessary circuits are inside of the LTC7103-1 to minimize external components and simplify design. The LTC7103-1 has wide operating range from 4.4V to 105V. A 40ns minimum on-time, together with 100% maximum duty cycle allow practical use at any output voltage between 1V and VIN. The switching frequency can be programmed either via an oscillator resistor or an external clock over a 200kHz to 2MHz range. Additional features include a fast and accurate output current programming and monitoring, and ultralow EMI/EMC emissions.
The demo board has an EMI filter installed. The EMI performance of the board (with EMI filter) is shown in Figure 2 in the demo manual. The figure shows that the circuit passes the CISPR 25 radiated emission 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 +VIN_EMI turret pin.
The demo board provides current monitor and output clock signal to interface with an external application circuit. User selectable mode selection (JP1) is provided and Burst Mode® operation position is selected by default. Burst Mode operation increases light load efficiency while pulse-skipping mode allows constant-frequency operation to a lighter load. Forced continuous mode improves output voltage ripple at light load by allowing constant-frequency operation for entire range of output load. This demo board allows phase-locked loop (PLL) synchronization to an external clock by selecting SYNC mode on JP1 and by providing a clock signal on CLKIN turret.
The LTC7103-1 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 DC2833A. The LTC7103-1 is assembled in the 36 (26) lead QFN package. Proper board layout is essential for maximum thermal and electrical performance. See the data sheet sections for details.
