RT9277APF datasheet(11/12 Pages) RICHTEK

11 / 12 page

RT9277A/B

Preliminary

DS9277A/B-02 March 2007

www.richtek.com

The best criterion to optimize the loop compensation is

by inspecting the transient response and adjusting the

compensation network.

Soft-Start Capacitor

The soft-start function begins from VSS = 0V to VSS = 1.24V

with a 4

μA constant current charging to the soft-start

capacitor, so the capacitor should be large enough to let

the output voltage reach regulation inside the soft-start

cycle. Typical value of soft-start capacitor range is from

10nF to 200nF. After the cycle finished, the load can start

to draw maximum current as required.

Layout Guideline

For high frequency switching power supplies, the PCB

layout is important step in system application design. In

order to let IC achieve good regulation, high efficiency and

stability, it is strongly recommended the power

components should be placed as close as possible. These

traces should be wide and short. The feedback pin and the

networks of feedback and compensation should keep away

from the power loops, and be shielded with a ground trace

or plane to prevent noise coupling.

OUT

ESR

OUT

0.005

0.4

200

RT9277APF Datasheet(PDF) 11 Page - Richtek Technology Corporation