AP61300/AP61302

Document number: DS43404 Rev. 3 - 2

16 of 21

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November 2022

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AP61300/AP61302

Application Information (continued)

9

Setting the Output Voltage

The AP61300/AP61302 has adjustable output voltages, starting from 0.6V, using an external resistive divider. 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. R2 can be determined by the following equation:

������������ =

������. ������ ∙ ������������

������������������������ − ������. ������������

Eq. 5

Table 1 shows a list of recommended component selections for common AP61300/AP61302 output voltages referencing Figure 1 and Figure 2.

Table 1. Recommended Component Selections

AP61300/AP61302

Output Voltage (V)

R1 (kΩ)

R2 (kΩ)

L (µH)

C1 (µF)

C2 (µF)

C3 (pF)

AP61300

AP61302

1.0

200.0

301.0

1.0

22

22

OPEN

33

1.2

200.0

200.0

1.0

22

22

OPEN

33

1.5

200.0

133.0

1.0

22

22

OPEN

33

1.8

200.0

100.0

1.0

22

22

OPEN

33

2.5

200.0

63.2

1.0

22

22

OPEN

33

3.3

200.0

44.2

1.0

22

22

OPEN

33

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. 6

Where:



∆IL is the inductor current ripple



fSW is the buck converter switching frequency

For AP61300/AP61302

, choose ∆IL to be 30% to 50% of the maximum load current of 3A.

The inductor peak current is calculated by:

������������

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

∆������������

������

Eq. 7

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 0.47µH to 2.2µH

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 30

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