Datasheet

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INDUCTOR SELECTION
DI
L
+
V
O
V
I
V
I
* V
O
L ƒ
sw
DI
L(MAX)
+ I
O(MAX)
)
DI
L
2
(4)
OUTPUT CAPACITOR SELECTION
DV
O
+
V
O
V
I
V
I
* V
O
L ƒ
sw
ǒ
1
8 C
O
ƒ
sw
) ESR
Ǔ
, maximum for high V
I
(5)
TPS62300, TPS62301, TPS62302
TPS62303, TPS62304, TPS62305,
TPS62311, TPS62313, TPS62315, TPS62320, TPS62321
SLVS528E – JULY 2004 – REVISED NOVEMBER 2007
Even though the inductor does not influence the operating frequency, the inductor value has a direct effect on the
ripple current. The selected inductor has to be rated for its dc resistance and saturation current. The inductor
ripple current ( Δ I
L
) decreases with higher inductance and increases with higher V
I
or V
O
.
with: f
SW
= switching frequency (3 MHz typical)
L = inductor value
Δ I
L
= peak-to-peak inductor ripple current
I
L(MAX)
= maximum inductor current
Normally, it is advisable to operate with a ripple of less than 30% of the average output current. Accepting larger
values of ripple current allows the use of low inductances, but results in higher output voltage ripple, greater core
losses, and lower output current capability.
The total losses of the coil consist of both the losses in the DC resistance (R
(DC)
) and the following
frequency-dependent components:
• The losses in the core material (magnetic hysteresis loss, especially at high switching frequencies)
• Additional losses in the conductor from the skin effect (current displacement at high frequencies)
• Magnetic field losses of the neighboring windings (proximity effect)
• Radiation losses
The following inductor series from different suppliers have been used with the TPS6230x, TPS6231x, and
TPS6232x converters.
Table 2. List of Inductors
MANUFACTURER SERIES DIMENSIONS
FDK MIPW3226 3.2 x 2.6 x 1 = 8.32 mm
3
MIPSA2520 2.5 x 2.0 x 1.2 = 6 mm
3
Murata LQM2HP 2.5 x 2.0 x 1.2 = 6 mm
3
LQ CB2016 2 x 1.6 x 1.6 = 5.12 mm
3
Taiyo Yuden LQ CB2012 2 x 1.2 x 1.2 = 2.88 mm
3
LQ CBL2012 2 x 1.2 x 1 = 2.40 mm
3
TDK VLF3010AT 2.8 x 2.6 x 1 = 7.28 mm
3
Coilcraft LPS3010 3.3 x 3.3 x 1 = 10.89 mm
3
JFE 32R1560 3.2 x 2.5 x 0.6 = 4.8 mm
3
The advanced fast-response voltage mode control scheme of the TPS6230x, TPS6231x, and TPS6232x allows
the use of tiny ceramic capacitors. Ceramic capacitors with low ESR values have the lowest output voltage ripple
and are recommended. The output capacitor requires either an X7R or X5R dielectric. Y5V and Z5U dielectric
capacitors, aside from their wide variation in capacitance over temperature, become resistive at high frequencies.
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:
At light loads, 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 and propagation delays.
The typical output voltage ripple is 1.5% of the nominal output voltage V
O
.
Copyright © 2004 – 2007, Texas Instruments Incorporated Submit Documentation Feedback 19
Product Folder Link(s): TPS62300, TPS62301, TPS62302 TPS62303, TPS62304, TPS62305, TPS62311, TPS62313,
TPS62315, TPS62320, TPS62321