AP63356/AP63357

Document number: DS41949 Rev. 3 - 2

18 of 29

www.diodes.com

August 2019

© Diodes Incorporated

AP63356/AP63357

Application Information (cont.)

10

Setting the Output Voltage (continued)

Table 2 shows a list of recommended component selections for common AP63356/AP63357 output voltages referencing Figure 40 using external

compensation.

AP63356

AP63357

VIN

EN

SW

BST

FB

GND

PG

COMP

INPUT

C1

R1

C4

R2

L

C3

C2

OUTPUT

R5

C5

C6

Figure 40. Typical Application Circuit Using External Compensation

Table 2. Recommended Components Selections Using External Compensation

AP63356/AP63357

Output Voltage

(V)

R1

(k

)

R2

(k

)

L

(µH)

C1

(µF)

C2

(µF)

C3

(nF)

C4

(pF)

R5

(k

)

C5

(nF)

C6

(pF)

2.5

62

30

3.3

10

2 x 22

100

OPEN

27

3.9

OPEN

3.3

91

30

4.7

10

3 x 22

100

OPEN

27

3.3

OPEN

5.0

157

30

6.8

10

3 x 22

100

OPEN

38

3.3

OPEN

12.0

422

30

10.0

10

4 x 22

100

OPEN

47

6.8

OPEN

11

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. 7

Where:



∆IL is the inductor current ripple



fSW is the buck converter switching frequency

For AP63356/AP63357

, choose ∆IL to be 30% to 50% of the maximum load current of 3.5A.

The inductor peak current is calculated by:

Eq. 8

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 2.2µH to 10µH

with a D

C current rating of at least 35% higher than the maximum load current. For highest efficiency, the inductor’s DC resistance should be less

than 3

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