MIC2168ABMM datasheet(13/14 Pages) MICREL

13 / 14 page

April 2005

M9999-062205

MIC2168A

Micrel, Inc.

Design Example

Layout and Checklist:

1. Connect the current limiting (CS) resistor directly

to the drain of top MOSFET Q1.

2. Connect the VSW pin directly to the source of top

MOSFETQ1thrua4Ωto10Ωresistor.Thepurpose

of this resistor is to ﬁlter the switch node.

3. ThefeedbackresistorsR1andR2shouldbeplaced

close to the FB pin. The top side of R1 should

connect directly to the output node. Run this trace

away from the switch node (junction of Q1, Q2, and

L1). The bottom side of R1 should connect to the

GND pin on the MIC2168A.

4. The compensation resistor and capacitors should

be placed right next to the COMP/EN pin and the

other side should connect directly to the GND pin

on the MIC2168A rather than going to the plane.

5. The input bulk capacitors should be placed close

to the drain of the top MOSFET.

6. The 1µF ceramic capacitor should be placed right

on the VIN pin of the MIC2168A.

7. The 4.7µF to 10µF ceramic capacitor should be

placed right on the VDD pin.

8. The source of the bottom MOSFETshould connect

directly to the input capacitor GND with a thick

trace. The output capacitor and the input capacitor

should connect directly to the GND plane.

9. Place a 0.1µF ceramic capacitor in parallel with

the CS resistor to ﬁlter any switching noise.

MIC2168ABMM Datasheet(PDF) 13 Page - Micrel Semiconductor