MP5403B

– DUAL BUCK AND ONE LOAD SWITCH PMIC

MP5403B Rev. 1.0

www.MonolithicPower.com

21

12/5/2017

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Output Capacitor Selection

The output capacitor limits the output voltage

ripple and ensures a stable regulation loop.

Select an output capacitor with low impedance at

the switching frequency. Use ceramic capacitors

with X5R or X7R dielectrics. Using an electrolytic

capacitor may result in additional output voltage

ripple, thermal issues, and require additional

care in selecting the feedback resistor (R1) due

to the large ESR. For most applications, a 22µF

capacitor is sufficient.

PCB Layout Guidelines

Efficient PCB layout of the switching power

supplies is critical for stable operation. If the

layout is not done carefully, for the high switching

frequency converter especially, the regulator

could show poor line or load regulation and

stability issues. For best results, refer to Figure 4

and follow the guideline below.

1. Place the input capacitor as close to the IC

pins as possible for the high-speed step-

down regulator to provide clean control

voltage.

1

1

1

2

VIN1

VIN2

GND

VOUT1

VOUT2

GND

VIN3

VOUT3

GND

GND

C1A

C1B

C2

C3

C4

C5

C6

L1

L2

C7

R1

R2

R3

R4

EN1

EN2

EN3

PG3

PG2

PG1

Top Layer

GND

VIN3

Vout1 Sense

Vout2 Sense

Bottom Layer

Figure 4: Recommended Layout