SW

IN

OUT

OUT

L

L

MAX

,

OUT

MAX

,

L

f

L

V

V

1

V

I

2

I

I

I

´

-

´

=

D

D

+

=

÷

ø

ö

ç

è

æ

+

´

=

÷

ø

ö

ç

è

æ

+

´

=

2

1

1

6

.

0

2

1

1

R

R

V

R

R

V

V

FB

OUT

10

TLV62568, TLV62568P

SLVSD89A – NOVEMBER 2016 – REVISED APRIL 2017

www.ti.com

Product Folder Links: TLV62568 TLV62568P

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Copyright © 2016–2017, Texas Instruments Incorporated

(1)

Inductor tolerance and current de-rating is anticipated. The effective inductance can vary by +20% and -30%.

(2)

Capacitor tolerance and bias voltage de-rating is anticipated. The effective capacitance can vary by +20% and -50%.

(3)

This LC combination is the standard value and recommended for most applications.

When sizing R2, in order to achieve low current consumption and acceptable noise sensitivity, use a maximum of

200 kΩ for R2. Larger currents through R2 improve noise sensitivity and output voltage accuracy but increase

current consumption.

(2)

A feed forward capacitor, C3 improves the loop bandwidth to make a fast transient response (shown in

Figure 19). 6.8-pF capacitance is recommended for R2 of 100-kΩ resistance. A more detailed discussion on the

optimization for stability vs. transient response can be found in SLVA289.

8.2.2.2 Output Filter Design

The inductor and output capacitor together provide a low-pass filter. To simplify this process, Table 4 outlines

possible inductor and capacitor value combinations. Checked cells represent combinations that are proven for

stability by simulation and lab test. Further combinations should be checked for each individual application.

Table 4. Matrix of Output Capacitor and Inductor Combinations

(2)

4.7

10

22

2x 22

100

0.6

1

+

2.2

1.2

1

+

+

2.2

+

1.8

1

+

+

+

2.2

+

+

8.2.2.3 Inductor Selection

The main parameters for inductor selection is inductor value and then saturation current of the inductor. To

calculate the maximum inductor current under static load conditions, Equation 3 is given:

where:

•

•

•

•

L is the inductor value

(3)

It is recommended to choose a saturation current for the inductor that is approximately 20% to 30% higher than

inductor.

8.2.2.4 Input and Output Capacitor Selection

The architecture of the TLV62568 allows use of tiny ceramic-type output capacitors with low equivalent series

resistance (ESR). These capacitors provide low output voltage ripple and are thus recommended. To keep its

resistance up to high frequencies and to achieve narrow capacitance variation with temperature, it is

recommended to use X7R or X5R dielectric.