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DIL + Vout

1– Vout

Vin

L

f

I

DIL

2

f = switching frequency (1 MHz typical, 650 kHz minimal)

L = inductor valfue

INPUT CAPACITOR SELECTION

OUTPUT CAPACITOR SELECTION

TPS62200

,, TPS62201

TPS62202, TPS62203, TPS62207

TPS62204, TPS62205, TPS62208

SLVS417E – MARCH 2002 – REVISED MAY 2006

APPLICATION INFORMATION (continued)

The inductor value determines the inductor ripple current. The larger the inductor value, the smaller the inductor

ripple current, and the lower the conduction losses of the converter. On the other hand, larger inductor values

cause a slower load transient response. Usually the inductor ripple current, as calculated below, is around 20%

of the average output current.

In order to avoid saturation of the inductor, the inductor should be rated at least for the maximum output current

of the converter plus the inductor ripple current that is calculated as

The highest inductor current occurs at maximum Vin.

A more conservative approach is to select the inductor current rating just for the maximum switch current of

670 mA. Refer to Table 1 for inductor recommendations.

Table 1. Recommended Inductors

INDUCTOR VALUE

COMPONENT SUPPLIER

COMMENTS

10 µH

Sumida CDRH5D28-100

High efficiency

10 µH

Sumida CDRH5D18-100

10 µH

Sumida CDRH4D28-100

10 µH

Coilcraft DO1608-103

6.8 µH

Sumida CDRH3D16-6R8

Smallest solution

10 µH

Sumida CDRH4D18-100

10 µH

Sumida CR32-100

10 µH

Sumida CR43-100

10 µH

Murata LQH4C100K04

Because the buck converter has a pulsating input current, a low ESR input capacitor is required. This results in

the best input voltage filtering and minimizing the interference with other circuits caused by high input voltage

spikes. Also the input capacitor must be sufficiently large to stabilize the input voltage during heavy load

transients. For good input voltage filtering, usually a 4.7 µF input capacitor is sufficient. It can be increased

without any limit for better input-voltage filtering. If ceramic output capacitors are used, the capacitor RMS ripple

current rating always meets the application requirements.

Ceramic capacitors show a good performance because of the low ESR value, and they are less sensitive

against voltage transients and spikes compared to tantalum capacitors.

Place the input capacitor as close as possible to the input pin of the device for best performance (refer to

Table 2 for recommended components).

The advanced fast response voltage mode control scheme of the TPS6220x allows the use of tiny ceramic

capacitors with a value of 10 µF without having large output voltage under and overshoots during heavy load

transients.

Ceramic capacitors with low ESR values have the lowest output voltage ripple and are therefore recommended.

If required, tantalum capacitors may be used as well (refer to Table 2 for recommended components).

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