O

RMS

I

I

=

2

O

O

RMS

O(max)

I

I

V

V

I

= I

1

V

V

æ

ö

´

´

-

ç

÷

è

ø

O

I

O

O

O

V

1

V

1

V

= V

ESR

L

8

C

f

f

-

æ

ö

D

´

´

+

ç

÷

´

´

´

è

ø

1

2

3

O

O

I

RMS(C )

O

V

1

V

I

= V

L

f

-

´

´

´

´

TPS62000, TPS62001, TPS62002, TPS62003

TPS62004, TPS62005, TPS62006, TPS62007, TPS62008

SLVS294F – SEPTEMBER 2000 – REVISED AUGUST 2015

www.ti.com

See Table 3 for recommended capacitors.

If an output capacitor is selected with an ESR value

≤ 120 mΩ, its RMS ripple current rating always meets the

application requirements. Just for completeness, the RMS ripple current is calculated as:

(5)

The overall output ripple voltage is the sum of the voltage spike caused by the output capacitor ESR plus the

voltage ripple caused by charging and discharging the output capacitor:

(6)

Table 3. Tested Capacitors

CAPACITOR VALUE

ESR/m

Ω

COMPONENT SUPPLIER

COMMENTS

10

μF

50

Taiyo Yuden JMK316BJ106KL

Ceramic

47

μF

100

Sanyo 6TPA47M

POSCAP

68

μF

100

Spraque 594D686X0010C2T

Tantalum

9.2.2.3 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.

The input capacitor should have a minimum value of 10

μF and can be increased without any limit for better input

voltage filtering.

The input capacitor should be rated for the maximum input ripple current calculated as:

(7)

The worst case RMS ripple current occurs at D = 0.5 and is calculated as:

Ceramic capacitor show a good performance because of their low ESR value, and they are less sensitive against

voltage transients compared to tantalum capacitors.

Place the input capacitor as close as possible to the input pin of the IC for best performance.

14

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