Datasheet
TPS62040
TPS62042, TPS62043
TPS62044, TPS62046
SLVS463B − JUNE 2003 − REVISED OCTOBER 2005
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15
Output Capacitor Selection
The advanced fast response voltage mode control scheme of the TPS6204x allows the use of small ceramic
capacitors with a typical value of 22 µF without having large output voltage under and overshoots during heavy load
transients. Ceramic capacitors having low ESR values have the lowest output voltage ripple and are recommended.
If required, tantalum capacitors may also be used. Refer to Table 2 for component selection.
If ceramic output capacitor are used, the capacitor RMS ripple current rating always meets the application
requirements. Just for completeness the RMS ripple current is calculated as:
I
RMSCout
+ V
O
1–
V
O
V
I
L ƒ
1
2 3
Ǹ
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:
DV
O
+ V
O
1–
V
O
V
I
L ƒ
ǒ
1
8 C
O
ƒ
) ESR
Ǔ
Where the highest output voltage ripple occurs at the highest input voltage, V
I
.
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 nominal output voltage.
Input Capacitor Selection
Because of the nature of the buck converter having a pulsating input current, a low ESR input capacitor is required
for best input voltage filtering and minimizing the interference with other circuits caused by high input voltage spikes.
The input capacitor should have a minimum value of 22 µF. The input capacitor can be increased without any limit
for better input voltage filtering.
Table 2. Input and Output Capacitor Selection
CAPACITOR
VALUE
CASE SIZE COMPONENT SUPPLIER COMMENTS
22 µF 1206 Taiyo Yuden JMK316BJ226ML Ceramic
22 µF 1210 Taiyo Yuden JMK325BJ226MM Ceramic
(8)
(9)