RT9218B

14

DS9218B-09 March 2007

www.richtek.com

Figure 10. The connections of the critical components in the converter

of them represents numerous physical capacitors. Use a dedicated grounding plane and use vias to ground all critical

components to this layer. Apply another solid layer as a power plane and cut this plane into smaller islands of common

voltage levels. The power plane should support the input power and output power nodes. Use copper filled polygons on the

top and bottom circuit layers for the PHASE node, but it is not necessary to oversize this particular island. Since the

PHASE node is subjected to very high dV/dt voltages, the stray capacitance formed between these island and the

surrounding circuitry will tend to couple switching noise. Use the remaining printed circuit layers for small signal routing.

The PCB traces between the PWM controller and the gate of MOSFET and also the traces connecting source of MOSFETs

should be sized to carry 2A peak currents.

Below PCB gerber files are our test board for your reference :

LOAD

VCC

GND

RT9218B

FB

LGATE

UGATE

IL

IQ1

V

OUT

Q2

Q1

IQ2

5V/12V

GND