I

2

I

1 *

Vout

Vin

L

ƒ

1

2

3

TPS62060

SLVSA95 – MARCH 2010

www.ti.com

(2)

With:

f = Switching Frequency (3MHz typical)

L = Inductor Value

A more conservative approach is to select the inductor current rating just for the switch current of the converter.

Accepting larger values of ripple current allows the use of lower inductance values, but results in higher output

voltage ripple, greater core losses, and lower output current capability.

The total losses of the coil have a strong impact on the efficiency of the DC/DC conversion and consist of both

•

The losses in the core material (magnetic hysteresis loss, especially at high switching frequencies)

•

Additional losses in the conductor from the skin effect (current displacement at high frequencies)

•

Magnetic field losses of the neighboring windings (proximity effect)

•

Radiation losses

Table 2. List of Inductors

INDUCTANCE mH

INDUCTOR TYPE

SUPPLIER

3.2 x 2.5 x 1.2 max

1.0

MIPSAZ3225D

FDK

3.2 x 2.5 x 1.0 max

1.0

LQM32PN (MLCC)

Murata

3.7 x 4 x 1.8 max

1.0

LQH44 (wire wound)

Murata

4.0 x 4.0 x 2.6 max

1.2

NRG4026T (wire wound)

Taiyo Yuden

3.5 x 3.7 x 1.8 max

1.2

DE3518 (wire wound)

TOKO

Output Capacitor Selection

The advanced fast-response voltage mode control scheme of the TPS62060 allows the use of tiny ceramic

capacitors. Ceramic capacitors with low ESR values have the lowest output voltage ripple and are

recommended. The output capacitor requires either an X7R or X5R dielectric. Y5V and Z5U dielectric capacitors,

aside from their wide variation in capacitance over temperature, become resistive at high frequencies and may

not be used. For most applications a nominal 10µF or 22µF capacitor is suitable. At small ceramic capacitors, the

DC-bias effect decreases the effective capacitance. Therefore a 22µF capacitor can be used for output voltages

higher than 2V, see list of capacitors.

In case additional ceramic capacitors in the supplied system are connected to the output of the DC/DC converter,

range. In this case a loop stability analysis must be performed as described later.

At nominal load current, the device operates in PWM mode and the RMS ripple current is calculated as:

(3)

Input Capacitor Selection

Because of the nature of the buck converter having a pulsating input current, a low ESR input capacitor is

required for best input voltage filtering and minimizing the interference with other circuits caused by high input

voltage spikes. For most applications a 10µF ceramic capacitor is recommended. The input capacitor can be

increased without any limit for better input voltage filtering.

16

Submit Documentation Feedback

Copyright © 2010, Texas Instruments Incorporated

Product Folder Link(s) :TPS62060