MIC2168_05 Datasheet, PDF (13/14 Pages) Micrel Semiconductor – 1MHz PWM Synchronous Buck Control IC

MIC2168
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
MOSFET Q1 thru a 4Ω to 10Ω resistor. The purpose
of this resistor is to filter the switch node.
3. The feedback resistors R1 and R2 should be placed
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 MIC2168.
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 MIC2168 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 MIC2168.
7. The 4.7µF to 10µF ceramic capacitor should be
placed right on the VDD pin.
8. The source of the bottom MOSFET should 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.
Micrel, Inc.
April 2005
13
M9999-040805