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Output Capacitor Selection
V
out

I
out
C
out


1
f
s

I
p
 L
V
out
 V
d
 V
in

 I
p
 ESR
Input Capacitor Selection
Rectifier Diode Selection
TPS65100 , TPS65101
TPS65105
SLVS496C – SEPTEMBER 2003 – REVISED APRIL 2006
APPLICATION INFORMATION (continued)
Table 1. Inductor Selection
DEVICE INDUCTOR VALUE COMPONENT SUPPLIER DIMENSIONS / mm ISAT/DCR
4.7 µ H Coilcraft DO1813P-472HC 8,89 x 6,1 x 5 2.6 A/54 m Ω
4.2 µ H Sumida CDRH5D28 4R2 5,7 x 5,7 x 3 2.2 A/23 m Ω
4.7 µ H Sumida CDC5D23 4R7 6 x 6 x 2,5 1.6 A/48 m Ω
TPS65100
3.3 µ H Wuerth Elektronik 744042003 4,8 x 4,8 x 2 1.8 A/65 m Ω
4.2 µ H Sumida CDRH6D12 4R2 6,5 x 6,5 x 1,5 1.8 A/60 m Ω
3.3 µ H Sumida CDRH6D12 3R3 6,5 x 6,5 x 1,5 1.9 A/50 m Ω
3.3 µ H Sumida CDPH4D19 3R3 5,1 x 5,1 x 2 1.5 A/26 m Ω
3.3 µ H Coilcraft DO1606T-332 6,5 x 5,2 x 2 1.4 A/120 m Ω
TPS65105 3.3 µ H Sumida CDRH2D18/HP 3R3 3,2 x 3,2 x 2 1.45 A/69 m Ω
4.7 µ H Wuerth Elektronik 744010004 5,5 x 3,5 x 1 1.0 A/260 m Ω
3.3 µ H Coilcraft LPO6610-332M 6,6 x 5,5 x 1 1.3 A/160 m Ω
For the best output voltage filtering, a low ESR output capacitor is recommended. Ceramic capacitors have a
low ESR value, but depending on the application, tantalum capacitors can be used as well. A 22- µ F ceramic
output capacitor works for most of the applications. Higher capacitor values can be used to improve the load
transient regulation. See Table 2 for selection of the output capacitor. The output voltage ripple can be
calculated as:
with:
IP = Peak switch current as calculated in the previous section with I
SW(peak)
.
L = Selected inductor value
I
OUT
= Normal load current
f
s
= Switching frequency
V
d
= Rectifier diode forward voltage (typical 0.3 V)
C
OUT
= Selected output capacitor
ESR = Output capacitor ESR value
For good input voltage filtering, low ESR ceramic capacitors are recommended. A 22- µ F ceramic input capacitor
is sufficient for most of the applications. For better input voltage filtering, this value can be increased. See
Table 2 and the typical applications for input capacitor recommendations.
Table 2. Input and Output Capacitors Selection
CAPACITOR VOLTAGE RATING COMPONENT SUPPLIER COMMENTS
22 µ F/1210 16 V Taiyo Yuden EMK325BY226MM C
out
22 µ F/1206 6.3 V Taiyo Yuden JMK316BJ226 C
in
To achieve high efficiency, a Schottky diode should be used. The voltage rating should be higher than the
maximum output voltage of the converter. The average forward current should be equal to the average inductor
current of the converter. The main parameter influencing the efficiency of the converter is the forward voltage
and the reverse leakage current of the diode; both should be as low as possible. Possible diodes are: On
Semiconductor MBRM120L, Microsemi UPS120E, and Fairchild Semiconductor MBRS130L.
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