Datasheet

DV
out
+
I
out
C
out
ƪ
1
f
s
*
I
p
L
V
out
) V
d
* V
in
ƫ
) I
p
ESR
TPS65140, TPS65141
TPS65145
SLVS497E –SEPTEMBER 2003–REVISED NOVEMBER 2012 www.ti.com
Table 1. Inductor Selection
DEVICE INDUCTOR VALUE COMPONENT SUPPLIER DIMENSIONS / mm ISAT/DCR
4.7 μH Coilcraft DO1813P-472HC 8,89 x 6,1 x 5 2.6 A/54 mΩ
4.2 μH Sumida CDRH5D28 4R2 5,7 x 5,7 x 3 2.2 A/23 mΩ
4.7 μH Sumida CDC5D23 4R7 6 x 6 x 2,5 1.6 A/48 mΩ
TPS65140
3.3 μH Wuerth Elektronik 744042003 4,8 x 4,8 x 2 1.8 A/65 mΩ
4.2 μH Sumida CDRH6D12 4R2 6,5 x 6, 5 x 1,5 1.8 A/60 mΩ
3.3 μH Sumida CDRH6D12 3R3 6,5 x 6,5 x 1,5 1.9 A/50 mΩ
3.3 μH Sumida CDPH4D19 3R3 5,1 x 5,1 x 2 1.5 A/26 mΩ
3.3 μH Coilcraft DO1606T-332 6,5 x 5,2 x 2 1.4 A/120 mΩ
TPS65145 3.3 μH Sumida CDRH2D18/HP 3R3 3,2 x 3,2 x 2 1.45 A/69 mΩ
4.7 μH Wuerth Elektronik 744010004 5,5 x 3,5 x 1 1 A/260 mΩ
3.3 μH Coilcraft LPO6610-332M 6,6 x 5,5 x 1 1.3 A/160 mΩ
Output Capacitor Selection
For 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-μF ceramic output
capacitor works for most of the applications. Higher capacitor values can be used to improve load transient
regulation. See Table 2 for the 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
Input Capacitor Selection
For good input voltage filtering, low ESR ceramic capacitors are recommended. A 22-μF ceramic input capacitor
is sufficient for most of 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 μF/1210 16 V Taiyo Yuden EMK325BY226MM C
O
22 μF/1206 6.3 V Taiyo Yuden JMK316BJ226 C
I
Rectifier Diode Selection
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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