AP64060

Document number: DS44123 Rev. 2 - 2

13 of 18

www.diodes.com

August 2022

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AP64060

Application Information (continued)

9

Setting the Output Voltage

The AP64060 has adjustable output voltages starting from 0.8V using an external resistive divider. An optional external capacitor, C4 in Figure 1,

of 10pF to 220pF improves the transient response. The resistor values of the feedback network are selected based on a design trade-off between

efficiency and output voltage accuracy. There is less current consumption in the feedback network for high resistor values, which improves

efficiency at light loads. However, values too high cause the device to be more susceptible to noise affecting its output voltage accuracy. R1 can

be determined by the following equation:

������������ = ������������ ∙ (

������������������������

������. ������������

− ������)

Eq. 4

Table 1 shows a list of recommended component selections for common AP64060 output voltages referencing Figure 1.

Table 1. Recommended Component Selections

AP64060

Output Voltage

(V)

R1

(k

Ω)

R2

(k

Ω)

L

(µH)

CIN

(µF)

COUT

(µF)

C3

(nF)

C4

(pF)

1.8

27.4

22.1

4.7

2.2

10x2

100

OPEN

2.5

47.5

22.1

6.8

2.2

10x2

100

OPEN

3.3

69.8

22.1

8.2

2.2

10x2

100

OPEN

5.0

115

22.1

10

2.2

10x2

100

OPEN

12.0

309

22.1

22

2.2

10x3

100

OPEN

10

Inductor

Calculating the inductor value is a critical factor in designing a buck converter. For most designs, the following equation can be used to calculate

the inductor value:

������ =

������������������������ ∙ (������������������ − ������������������������)

������������������ ∙ ∆������������ ∙ ������������������

Eq. 5

Where:



∆IL is the inductor current ripple



fSW is the buck converter switching frequency

For the AP64060

, choose ∆IL to be 20% to 30% of the maximum load current of 1A.

The inductor peak current is calculated by:

������������

������������������������ = ������������������������������ +

∆������������

������

Eq. 6

Peak current determines the required saturation current rating, which influences the size of the inductor. Saturating the inductor decreases the

converter efficiency while increasing the temperatures of the inductor and the internal power MOSFETs. Therefore, choosing an inductor with the

appropriate saturation current rating is important. For most applications, it is recommended to select an inductor of approximately 4.7µH to 22µH

with a DC current rating of at least 35% higher than the maximum load current. For

highest efficiency, the inductor’s DC resistance should be less

than 7

0mΩ. Use a larger inductance for improved efficiency under light load conditions.