MIC2159 datasheet(15/17 Pages) MICREL

15 / 17 page

Micrel

MIC2159

October 2006

M9999-101206

Design Example

Layout and Checklist:

1. Connect the current limiting resistor directly to the

drain of top MOSFET.

2. Use a resistor from the input supply to the VIN pin on

the MIC2159. Also, place a 1µF ceramic

Capacitor from this pin to GND, preferably not thru a via.

3. The feedback resistors should be placed close to the

FB pin. The top side of the resistor should connect

directly to the output node. Run this trace away from the

switch node. The bottom side of the lower resistor

should connect to the GND pin on the MIC2159.

4. The compensation resistor and capacitors should be

placed right next to the COMP pin and the other side

should connect directly to the GND pin on the MIC2159

rather than going to the plane.

5. Add a 1.4Ω resistor and a 1000pF capacitor from the

switch node to ground pin. See page 7, Current Limiting

section for more detail.

6. Add place holders for gate resistors on the top and

bottom MOSFET gate drives. If necessary, gate resistors

of 5Ω or less should be used.

7. Low gate charge MOSFETs should be used to

maximize efficiency.

8. Compensation component GND, feedback resistor

ground, chip ground should all run together and connect

to the output capacitor ground. See demo board layout,

bottom layer.

9. The 10µF ceramic capacitor should be placed

between the drain of the top MOSFET and the source of

the bottom MOSFET.

10. The 10µF ceramic capacitor should be placed right

on the VDD pin without any vias.

11. 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.

12. Place a 0.01µF to 0.1µF Ceramic capacitor in

parallel with the CS resistor to filter any switching noise.

MIC2159 Datasheet(PDF) 15 Page - Micrel Semiconductor

MIC2159 Datasheet(HTML) 15 Page - Micrel Semiconductor

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