Datasheet

SW
IN
OUT
OUTL
L
MAX,OUTMAX,L
fL
V
V
1
VI
2
I
II
´
-
´=D
D
+=
TPS62080, TPS62080A
TPS62081, TPS62082
www.ti.com SLVSAE8D –SEPTEMBER 2011–REVISED JULY 2013
APPLICATION INFORMATION
Output Filter Design
The inductor and the output capacitor together provide a low pass frequency filter. To simplify this process
Table 4 outlines possible inductor and capacitor value combinations for the most application.
Table 4. Matrix of Output Capacitor / Inductor Combinations
C
OUT
[µF]
(1)
L [µH]
(1)
10 22 47 100 150
0.47
1 + +
(2)(3)
+ +
2.2 + + + +
4.7
(1) Capacitance tolerance and bias voltage de-rating is anticipated. The effective capacitance can vary
by+20% and -50%. Inductor tolerance and current de-rating is anticipated. The effective inductance
can vary by +20% and -30%.
(2) Plus mark indicates recommended filter combinations.
(3) Filter combination in typical application.
Inductor Selection
Main parameter for the inductor selection is the inductor value and then the saturation current of the inductor. To
calculate the maximum inductor current under static load conditions, Equation 4 is given.
(2)
Where
I
OUT,MAX
= Maximum output current
ΔI
L
= Inductor current ripple
f
SW
= Switching frequency
L = Inductor value
It's recommended to choose the saturation current for the inductor 20%~30% higher than the I
L,MAX
, out of
Equation 4. A higher inductor value is also useful to lower ripple current, but will increase the transient response
time as well. The following inductors are recommended to be used in designs.
Table 5. List of Recommended Inductors
INDUCTANCE CURRENT RATING DIMENSIONS DC RESISTANCE
TYPE MANUFACTURER
[µH] [mA] L x W x H [mm
3
] [mΩ typ]
1.0 2500 3 x 3 x 1.2 35 XFL3012-102ME Coilcraft
1.0 1650 3 x 3 x 1.2 40 LQH3NPN1R0NJ0 Murata
2.2 2500 4 x 3.7 x 1.65 49 LQH44PN2R2MP0 Murata
2.2 1600 3 x 3 x 1.2 81 XFL3012-222ME Coilcraft
Capacitor Selection
The input capacitor is the low impedance energy source for the converter which helps to provide stable
operation. A low ESR multilayer ceramic capacitor is recommended for best filtering and should be placed
between VIN and PGND as close as possible to that pins. For most applications 10μF will be sufficient, a larger
value reduces input current ripple.
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