MP1472 – 2A, 18V SYNCHRONOUS RECTIFIED, STEP-DOWN CONVERTER

MP1472 Rev. 1.0

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10

9/2/2011

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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:

S

ESR

f

1

2C2 R

2







If this is the case, then add the second

the location of the ESR zero. Determine the C6

value by the equation:

3

R

R

2

C

6

C

ESR





External Bootstrap Diode

An external bootstrap diode may enhance the

efficiency of the regulator, and it will be a must if

the applicable condition is:





duty cycle is high: D=

IN

OUT

V

V

>65%

In these cases, an external BST diode is

recommended from the output of the voltage

regulator to BST pin, as shown in Figure 2

MP1472

SW

BST

C

L

BST

C

5V or 3.3V

OUT

External BST Diode

IN4148

+

0.01

Figure 2—Add Optional External Bootstrap

Diode to Enhance Efficiency

The recommended external BST diode is IN4148,

and the BST cap is 0.01µF.