3A 32V Synchronous Rectified Step-Down

Converter

EC3286

Page 13 of 14

4J23N-Rev.F001

Where R3 is the compensation resistor.

3. Determine if the second compensation capacitor (C6) is required. It is required if the ESR

zero of the output capacitor is located at less than half of the switching frequency, or the

following relationship is valid:

If

this

is

the

case,

then

add

the

second

compensation capacitor (C6) to set the

pole fP3 at the location of the ESR zero. Determine the C6 value by the equation:

External Bootstrap Diode

An external bootstrap diode may enhance the efficiency of the regulator, the applicable

Duty cycle is high:

In these cases, an external BST diode is recommended from the output of the voltage regulator

to BST pin, as shown in Fig.14

Figure14.Add Optional External Bootstrap Diode to Enhance Efficiency

The recommended external BST diode is IN4148, and the BST

cap is 0.1~1μF.