L

L max

out max

I

I

I

2

D

=

+

L

Vout

1

Vin

I

Vout

L ƒ

-

D =

´

´

c

1

=

= 50kHz

2

(1 H

10 F)

f

p

´

´

´

TLV62065

SLVSAC4B – NOVEMBER 2010 – REVISED DECEMBER 2015

www.ti.com

Typical Application (continued)

8.2.2.2 Output Filter Design (Inductor and Output Capacitor)

The internal compensation network of TLV62065 is optimized for a LC output filter with a corner frequency of:

The device operates with nominal inductors of 1.0 µH to 1.2 µH and with 10 µF to 22 µF small X5R and X7R

ceramic capacitors. Please refer to the lists of inductors and capacitors. The device is optimized for a 1-µH

inductor and 10-µF output capacitor.

8.2.2.2.1

Inductor Selection

The inductor value has a direct effect on the ripple current. The selected inductor has to be rated for its DC

resistance and saturation current. The inductor ripple current (

ΔIL) decreases with higher inductance and

increases with higher VI or VO.

Equation 5 calculates the maximum inductor current in PWM mode under static load conditions. The saturation

current of the inductor should be rated higher than the maximum inductor current as calculated with Equation 6.

This is recommended because during heavy load transient the inductor current rises above the calculated value.

(5)

where

•

f = Switching frequency (3 MHz typical)

•

L = Inductor value

•

ΔIL = Peak-to-peak inductor ripple current

•

ILmax = Maximum inductor current

(6)

A more conservative approach is to select the inductor current rating just for the switch current limit ILIMF of the

converter.

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 DC resistance R(DC) and the following frequency-dependent components:

•

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 1. List of Inductors

DIMENSIONS [mm3]

INDUCTANCE

μH

INDUCTOR TYPE

SUPPLIER

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

12

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