AP64501

Document number: DS41980 Rev. 4 - 2

20 of 26

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August 2019

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AP64501

Application Information (cont.)

16

External Loop Compensation Design (cont.)

The following is an example of how to choose component values for external loop compensation. Actual component values used in the application

circuit may vary slightly from the calculated first-order approximation equations.

Let the following conditions be defined:



VIN = 12V



VOUT = 5V



IOUT = 5A



fsw = 570kHz



fc = 15kHz



R1 = 115

kΩ



R2 = 22.1kΩ



L = 3.6µH



C2 = 3 ×

22µF (Effectively, COUT ≈ 45µF)



RC ≈ 1mΩ

AP64501

VIN

EN

SW

BST

FB

GND

INPUT

R1

115kΩ

C4

R2

22.1kΩ

L

3.6μH

C3

100nF

C2

3 x 22µF

C1

10µF

OUTPUT

VOUT

5V

COMP

R5

C5

C6

SS

Css

10nF

VIN

12V

Figure 27. Example Circuit for Loop Compensation Calculations

The calculations of the main component values involved in the external loop compensation, R5 and C5, are required. If the optional C4 and C6

capacitors are used, their calculations are also required.