MCP1632 datasheet(21/34 Pages) MICROCHIP

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 2013 Microchip Technology Inc.

DS20005254A-page 21

MCP1632

5.3

PCB Layout Recommendations

The PCB layout is critical for switch-mode power

supplies. When developing the PCB, the designer must

follow the general rules for switching converters in

order to achieve consistent performance. The

guidelines include:

• Identify the high-current, high-frequency loops

before starting the PCB design. Figure 5-5 depicts

these loops for boost converters. I1 and I2 are the

main currents of the boost converter. The IRR is

the current produced by the reverse recovery of

the output rectifier D1. The IRR current is an

important source of noise/EMI.

• Minimize the area of the high-current loops. Use

copper planes or large traces for high-current

connections in order to minimize the parasitic

inductances.

• Four-layer PCBs with internal ground plane offer

the best performance for switch-mode power

supplies. For cost-sensitive applications,

two-layer PCBs can be used. In this case, the

bottom layer must be used like a ground plane.

• Use separate grounds for small-signal and power

signals. These grounds must be connected (when

possible) in a single point located near the GND

pin of the MCP1632 controller.

• Keep the current sense (CS) and feedback (FB)

signals away from noisy nodes, such as the drain

of the main switch (Q1).

• Locate the compensation network components

near the MCP1632 case.

FIGURE 5-5:

The Boost Converter’s Current Loops.

MCP1632

VIN

VOUT

VREF

COMP

VEXT

GND

VIN

RSLOPE

CIN

COUT

IRR

IDR

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