Datasheet

LPSMload
II D=
2
1
)(
÷
÷
÷
÷
÷
ø
ö
ç
ç
ç
ç
ç
è
æ
×
-
×=D
SW
IN
OUT
OUTL
fL
V
V
VI
(min)
(max)
(max)
1
TPS62140, TPS62140A
TPS62141, TPS62142, TPS62143
www.ti.com SLVSAJ0B –NOVEMBER 2011–REVISED JUNE 2013
(8)
where
I
L
(max) is the maximum inductor current
ΔI
L
is the peak-to-peak inductor ripple current
L(min) is the minimum effective inductor value
f
SW
is the actual PWM switching frequency
spacing
Calculating the maximum inductor current using the actual operating conditions gives the minimum required
inductor saturation current. It is recommended to add a margin of about 20%. A larger inductor value is also
useful to get lower ripple current, but increases the transient response time and size as well. The following
inductors have been used with the TPS6214X and are recommended for use:
Table 2. List of Inductors
Type Inductance [µH] Current [A]
(1)
Dimensions [L x B x H] MANUFACTURER
mm
XFL4020-222ME_ 2.2 µH, ±20% 3.5 4 x 4 x 2.1 Coilcraft
XFL4020-332ME_ 3.3 µH, ±20% 2.9 4 x 4 x 2.1 Coilcraft
IHLP1212BZ-11 2.2 µH, ±20% 3.0 3 x 3.6 x 2 Vishay
IHLP1616AB-11 2.2 µH, ±20% 2.75 4.05 x 4.45 x 1.2 Vishay
DEM4518C 1235AS-H-3R3M 3.3 µH, ±20% 2.5 4.5 x 4.7 x 1.9 Toko
(1) Lower of I
RMS
at 40°C rise or I
SAT
at 30% drop.
spacing
The inductor value also determines the load current at which the power-save mode is entered:
(9)
Using Equation 8, this current level can be adjusted by changing the inductor value.
Capacitor Selection
Output Capacitor
The recommended value for the output capacitor is 22 µF. The architecture of the TPS6214X allows the use of
tiny ceramic output capacitors with low equivalent series resistance (ESR). These capacitors provide low output-
voltage ripple and are recommended. To keep its low resistance up to high frequencies and to get narrow
capacitance variation with temperature, it is recommended to use X7R or X5R dielectric. Using a higher value
can have some advantages, like smaller voltage ripple and a tighter dc output accuracy in power-save mode (see
SLVA463).
Note: In power-save mode, the output voltage ripple depends on the output capacitance, its ESR and the peak
inductor current. Using ceramic capacitors provides small ESR and low ripple.
Input Capacitor
For most applications, 10 µF is sufficient and is recommended, though a larger value reduces input-current ripple
further. The input capacitor buffers the input voltage for transient events and also decouples the converter from
the supply. A low-ESR multilayer ceramic capacitor is recommended for best filtering and should be placed
between PVIN and PGND as close as possible to those pins. Even though AVIN and PVIN must be supplied
from the same input source, it is recommended to place a capacitance of 0.1 uF from AVIN to AGND, to avoid
potential noise coupling.
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Product Folder Links: TPS62140 TPS62140A TPS62141 TPS62142 TPS62143