Datasheet

TPS62040
TPS62042, TPS62043
TPS62044, TPS62046
SLVS463B − JUNE 2003 − REVISED OCTOBER 2005
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14
Inductor Selection
The TPS6204x typically uses a 6.2-µH output inductor. Larger or smaller inductor values can be used to optimize
the performance of the device for specific operation conditions. The selected inductor has to be rated for its dc
resistance and saturation current. The dc resistance of the inductance directly influences the efficiency of the
converter. Therefore an inductor with the lowest dc resistance should be selected for highest efficiency.
Formula (7) calculates the maximum inductor current under static load conditions. The saturation current of the
inductor should be rated higher than the maximum inductor current as calculated with formula (7). This is needed
because during heavy load transient the inductor current rises above the value calculated under (7).
DI
L
+ V
O
1–
V
O
V
I
L ƒ
I
L
max + I
O
max )
DI
L
2
with
ƒ = Switching frequency (1.25 MHz typical)
L = Inductor value
∆I
L
= Peak-to-peak inductor ripple current
I
L
max = Maximum inductor current
The highest inductor current occurs at maximum V
I
.
Open core inductors have a soft saturation characteristic and they can usually handle higher inductor currents versus
a comparable shielded inductor. A more conservative approach is to select the inductor current rating just for the
maximum switch current of 2.2 A for the TPS6204x. Keep in mind that the core material from inductor to inductor
differs and has an impact on the efficiency, especially at high switching frequencies. Refer to Table 1 and the typical
applications and inductors selection.
Table 1. Inductor Selection
INDUCTOR VALUE DIMENSIONS COMPONENT SUPPLIER
4.7 µH 5,0 mm × 5,0 mm × 3,0 mm Sumida CDRH4D28C-4.7
4.7 µH 5,2 mm × 5,2 mm × 2,5 mm Coiltronics SD25-4R7
5.3 µH 5,7 mm × 5,7 mm × 3,0 mm Sumida CDRH5D28-5R3
6.2 µH 5,7 mm × 5,7 mm × 3,0 mm Sumida CDRH5D28-6R2
6.0 µH 7,0 mm × 7,0 mm × 3,0 mm Sumida CDRH6D28-6R0
(6)
(7)