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TSZ02201-0F3F0AJ00170-1-2

© 2017 ROHM Co., Ltd. All rights reserved.

11.Dec.2017 Rev.001

www.rohm.com

TSZ22111

• 15 • 001

BD9E104FJ

VOUT

R2

FB

0.8V

R3

ERR

R1

Selection of Components Externally Connected - continued

*Be careful of total capacitance value, when additional capacitor CLOAD is connected to output capacitor COUT.

Use maximum additional capacitor CLOAD (Max) condition which satisfies the following method.

Maximum starting inductor ripple current IL_START can be expressed in the following method.

IL_START =

Maximum starting output current (IOUTMAX) +

Charge current to output capacitor(ICAP) +

∆IL

2

Charge current to output capacitor ICAP can be expressed in the following method.

[A]

Computation with VIN=12 V, VOUT=5 V, L=6.8 µH, IOUTMAX=1 A (Max), switching frequency fOSC=484 kHz (Min), Output

capacitor COUT=30 µF, Soft Start Time tSS=1.2 ms (Min), the method is as below.

[µF]

Confirm maximum starting inductor ripple current less than 2.1 A on actual equipment.

2.

Output Voltage Set Point

The output voltage value can be set by the feedback resistance ratio.

[V]

*Minimum pulse is 250 ns for BD9E104FJ.

Use input/output condition which satisfies the following

method.

[µs]

Maximum starting inductor ripple current IL_START

<

Over current limit 2.1 A (Min)

0.8

×

R

R

+

R

+

R

=

V

3

3

2

1

OUT

1.75





IN

OUT

V

V

250ns

Figure 47. Feedback Resistor Circuit

SS

OUT

LOAD

OUT

CAP

t

V

×

)

C

+

(C

=

I

127

≤



OUT

OUT

SS

L

OUTMAX

LOAD

C

-

V

t

×

)

2

ΔI

-

I

-

(2.1

(Max)

C