BD9325FJ-LB

BD9326EFJ-LB

BD9327EFJ-LB

2.

Selecting Application Components

(1) Output LC Constant (Buck Converter)

of the inductor.

Figure 18

Figure 19

equation.

Set with sufficient margin because the inductance L value may have a tolerance of ± 30%.

the drop voltage permissible value at the time of sudden load change.

Output ripple voltage is decided by the following equation.

Perform setting so that the voltage is within the permissible ripple voltage range.

However, 10μs is the rough calculation value of the DC/DC response speed.

Make Co settings so that these two values will be within the limit values.

(2) Loop Compensation

Choosing compensation Capacitor C1 and Resistor R3

The example of DC/DC converter application bode plot is shown in Figure 21. The compensation resistor R3 will set

resistor R3 has to be adjusted to adequate value for good stability and response speed.

Higher cross over frequency achieves good response speed, but less stability, and the lower cross over frequency

shows good stability, but worse response speed.

After that, please measure and adjust the cross over frequency on your set (on the actual application) to meet the

desired speed and phase-margin.

t

should not reach

the rated value level

Vo

L

Co

(

)

[ ]

A

f

V

V

V

V

L

I

CC

O

O

CC

L

1

1

×

×

−

×

=

∆

[ ]

V

f

V

V

C

I

R

I

V

CC

O

O

L

ESR

L

PP

1

2

×

×

∆

+

×

∆

=

∆

[ ]

V

s

C

I

V

O

L

DR

µ

10

×

∆

=

9/19

09.Sep.2014 Rev.003

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