Vout

Vin

1

1

Vout

Vout

ESR

L

f

8

Cout

f

-

æ

ö

D

=

´

´

+

ç

÷

´

´

´

è

ø

TPS62200, TPS62201, TPS62202, TPS62203

TPS62204, TPS62205, TPS62207, TPS62208

www.ti.com

SLVS417F – MARCH 2002 – REVISED JUNE 2015

8.2.2.3 Input Capacitor Selection

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. The capacitor 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 3

for recommended components).

8.2.2.4 Output Capacitor Selection

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 3 for recommended components).

At nominal load current the device operates in PWM mode and the overall output voltage ripple is the sum of the

voltage spike caused by the output capacitor ESR plus the voltage ripple caused by charging and discharging the

output capacitor:

where

•

the highest output voltage ripple occurs at the highest input voltage Vin.

(8)

At light load currents, the device operates in power save mode, and the output voltage ripple is independent of

the output capacitor value. The output voltage ripple is set by the internal comparator thresholds. The typical

output voltage ripple is 1% of the output voltage Vo.

Table 3. Recommended Capacitors

CAPACITOR VALUE

CASE SIZE

COMPONENT SUPPLIER

COMMENTS

4.7 µF

0805

Taiyo Yuden JMK212BY475MG

Ceramic

10 µF

0805

Taiyo Yuden JMK212BJ106MG

Ceramic

TDK C12012X5ROJ106K

Ceramic

10 µF

1206

Taiyo Yuden JMK316BJ106KL

Ceramic

TDK C3216X5ROJ106M

22 µF

1210

Taiyo Yuden JMK325BJ226MM

Ceramic

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