FTD8228

2014. 01. 04

11/12

Revision No : 0

The schottky diode reverse breakdown voltage should

be larger than the output voltage

Current Limit Program

:

A resistor between OC and GND pin programs peak switch

current.The resistor value should be between 26K and

240K.The current limit will be set from 0.5A to 4.5A.Keep

traces at this pin as short as possible.Do not put capacitance

at this pin. To set the over current trip point according to the

following equation:

Iocp=120000/R

Layout Design:

The layout design of FTD8228 regulator is relatively

simple. For the best efficiency and minimum noise

problems, we should place the following components

1) It is desirable to maximize the PCB copper area

connecting to GND pin to achieve the best thermal and

noise performance. If the board space allowed, a

ground plane is highly desirable.

.

3) The PCB copper area associated with LX pin must

be minimized to avoid the potential noise problem.

connecting to the FB pin must NOT be adjacent to the

LX net on the PCB layout to avoid the noise problem.

5) If the system chip interfacing with the EN pin has a

high impedance state at shutdown mode and the IN pin

is connected directly to a power source such as a Li-Ion

battery, it is desirable to add a pull down 1Mohm

resistor between the EN and GND pins to prevent the

noise from falsely turning on the regulator at shutdown

mode.