2 Evaluation Board Design

The LM2655 evaluation board is designed to supply 2.5 V at a maximum of 2.5A. The input voltage is from 4 V to 14 V. The board can be loaded with an SO-8 MOSFET as the lower switching element for lower switching losses than a Schottky Diode would provide by itself. The Schottky Diode, D1, improves efficiency.

Components were selected based on the design procedure in the LM2655 2.5A High Efficiency Synchronous Switching Regulator Data Sheet (SNVS072). The feedback resistors can be adjusted to achieve different output voltages. Use the formula:

where V_ref = 1.238 V.

PCB layout is critical to reduce noises and ensure specified performance. For layout guidelines, see the LM2655 2.5A High Efficiency Synchronous Switching Regulator Data Sheet (SNVS072). The artwork for this evaluation board is included in this document.

The schematic of the evaluation board is shown in Figure 4-2 and the parts list is given in Table 4-1.

The LM2655 has both under voltage and over voltage shutdown protection on the output as well as under voltage lock out on the input. When the under voltage protection occurs, the output voltage can be pulled below ground by the inductor. In applications that must be protected from reverse polarity, an output clamping diode can be added across C_OUT.