Datasheet

OUT
F
C = 5 x L x
H
m
m
( )
IN OUT IN
OUT OUT
LMAX
IN OUT
V x V V
V x I
I = +
0.8 x V 2 x V x f x L
-
MIN IN
s
L = V x 0.5
A
m
INMIN
UVLO
V
R3 = R4 x - 1
V
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ç ÷
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TPS61200
TPS61201
TPS61202
SLVS577D –MARCH 2007–REVISED MARCH 2013 www.ti.com
(2)
Inductor Selection
To make sure that the TPS6120X devices can operate, an inductor must be connected between the VIN and L
pins. To estimate the minimum inductance value, Equation 3 can be used.
(3)
In Equation 3, the minimum inductance, L
MIN
, for boost mode operation is calculated. V
IN
is the maximum input
voltage. The recommended inductor value range is between 1.5 μH and 4.7 μH. The minimum inductor value
should not be below 1.5 μH, even if Equation 3 yields something lower. Using 2.2 μH is recommended anyway
for getting best performance over the whole input and output voltage range.
With the chosen inductance value, the peak current for the inductor in steady state operation can be calculated
using Equation 4.
(4)
This would be the critical value for the current rating for selecting the inductor. It also needs to be taken into
account that load transients and error conditions may cause higher inductor currents. The following inductor
series from different suppliers have been used with TPS6120x converters:
Table 2. List of Inductors
VENDOR INDUCTOR SERIES
LPS3015
Coilcraft
LPS4012
Murata LQH3NP
Tajo Yuden NR3015
Wurth Elektronik WE-TPC Typ S
Capacitor Selection
Input Capacitor
At least a 4.7 μF input capacitor is recommended to improve transient behavior of the regulator and EMI
behavior of the total power supply circuit. An X5R or X7R ceramic capacitor placed as close as possible to the
VIN and PGND pins of the IC is recommended.
An R-C filter may be placed on the VIN pin to improve performance in applications with a noisy input source. A
100 Ω resistor and 0.1 µF capacitor are recommended in this case. This filter is not required operation.
Output Capacitor
For the output capacitor, it is recommended to use small X5R or X7R ceramic capacitors placed as close as
possible to the VOUT and PGND pins of the IC. If, for any reason, the application requires the use of large
capacitors which can not be placed close to the IC, using a smaller ceramic capacitor in parallel to the large one
is required. This small capacitor should be placed as close as possible to the VOUT and PGND pins of the IC.
To get an estimate of the recommended minimum output capacitance, Equation 5 can be used.
(5)
A capacitor with a value in the range of the calculated minimum should be used. This is required to maintain
control loop stability. There are no additional requirements regarding minimum ESR. There is also no upper limit
for the output capacitance value. Larger capacitors cause lower output voltage ripple as well as lower output
voltage drops during load transients.
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