7

AT9933

Design Example

The choice of the resistor dividers to set the input and output

current levels is illustrated by means of the design example

given below.

The parameters of the power circuit are:

V

V

V

I

f

Using these parameters, the values of the power stage in-

ductors and capacitor can be computed as (see Application

Note AN-H51 for details):

L1 = 82µH

L2 = 150µH

C1 = 0.22µF

The input and output currents for this design are:

I

ΔI

I

ΔI

Current Limits

The current sense resistor (R

resistors (R

The current sense resistor (R

resistors (R

The resistors can be chosen using the following equations:

(2)

(3)

Where I is the current (either I

peak ripple in the current (either ΔI

For the input side, the current level used in the equations

should be larger than the maximum input current so that it

does not interfere with the normal operation of the circuit.

The peak input current can be computed as:

(4)

+ 0.05V

+ 0.1V

Iin

= 1.706A

∆

2

Design Example Circuit

VIN

GATE

CS1

CS2

VDD

PWMD

REF

GND

VDC

VO

+

-

AT9933

D3