MIC2169 Datasheet, PDF (13/14 Pages) Micrel Semiconductor – 500 KHZ PWM SYNCHRONOUS BUCK CONTROL IC

MIC2169
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 pur-
pose of the 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 MIC2169.
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 MIC2169 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 MIC2169.
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
November 2003
13
M9999-111803