R1224N

How to Adjust Output Voltage and about Phase Compensation

Thus, with changing the value of R2 and R4, output voltage can be set in the specified range.

In the DC/DC converter, with the load current and external components such as L and C, phase might be behind

180 degree. In this case, the phase margin of the system will be less and stability will be worse. To prevent this,

phase margin should be secured with proceeding the phase. A pole is formed with external components L and

C3.

C3

L

1/2

~

Fpole

×

π

A zero (signal back to zero) is formed with R4 and C4.

≅Fzero~1/(2π×R4×C4)

For example, if L

=27µH, C3=47µF, the cut off frequency of the pole is approximately 4.5kHz.

To make the cut off frequency of the pole as much as 4.5kHz, set R4

=33kΩ and C4=1000pF.

=22kΩ is appropriate.

Ω is appropriate value.

CE CONTROL

C3

L

LOAD

C1

R1

C2

PMOS

SD

C4

R3

R4

R2

R1224N

EXT

GND

CE

5

1

2

3

4

9