www.ti.com

INMIN

UVLO

V

R3 = R4 x

- 1

V

æ

ö

ç

÷

ç

÷

è

ø

(2)

Inductor Selection

MIN

IN

s

L

= V

x 0.5

A

m

(3)

(

)

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

-

(4)

Capacitor Selection

Input Capacitor

Output Capacitor

OUT

F

C

= 5 x L x

H

m

m

(5)

TPS61200

TPS61201

TPS61202

SLVS577B – MARCH 2007 – REVISED FEBRUARY 2008

To make sure that the TPS6120X devices can operate, an inductor must be connected between pin VIN and pin

L. To estimate the minimum inductance value Equation 3 can be used.

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 in 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.

Equation 4 shows how to calculate the peak current I.

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 1. List of Inductors

VENDOR

INDUCTOR SERIES

LPS3015

Coilcraft

LPS4012

Murata

LQH3NP

Tajo Yuden

NR3015

Wurth Elektronik

WE-TPC Typ S

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. A ceramic capacitor placed as close as possible to the VIN and PGND

pins of the IC is recommended.

For the output capacitor, it is recommended to use small 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 recommended.

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.

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 drop during load transients.

16

Submit Documentation Feedback

Copyright © 2007–2008, Texas Instruments Incorporated

Product Folder Link(s): TPS61200 TPS61201 TPS61202