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DI
L
+ Vout
1–
Vout
Vin
L f
I
Lmax
+ I
outmax
)
DI
L
2
f = switching frequency (1 MHz typical, 650 kHz minimal)
L = inductor valfue
∆I
L
= peak-to-peak inductor ripple current
I
Lmax
= maximum inducator current
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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