2

O

I

L

L

O

L(max)

O(max)

V

1

V

I

I = V

I

I

L

f

-

D

D

´

=

+

´

(4)

OUTPUT CAPACITOR SELECTION

1

2

3

O

O

I

RMS(C )

O

V

1

V

I

= V

L

f

-

´

´

´

´

(5)

O

I

O

O

O

V

1

V

1

V

= V

ESR

L

8

C

f

f

-

æ

ö

D

´

´

+

ç

÷

´

´

´

è

ø

(6)

TPS62000-HT

SLVS917A – MARCH 2009 – REVISED JUNE 2009 .......................................................................................................................................................... www.ti.com

Where:

ƒ = Switching frequency (750 kHz typical)

L = Inductor value

ΔIL = Peak-to-peak inductor ripple current

IL(max) = Maximum inductor current

The highest inductor current occurs at maximum VI.

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

TPS62000 which is 1.6 A with ILIM = VIN and 900 mA with ILIM = GND. See Table 1 for recommended

inductors.

Table 1. Tested Inductors(1)

OUTPUT CURRENT

INDUCTOR VALUE

COMPONENT SUPPLIER

COMMENTS

Coilcraft DO3316P-103

Coilcraft DT3316P-103

High efficiency

Sumida CDR63B-100

0 mA to 600 mA

10

µH

Sumida CDRH5D28-100

Coilcraft DO1608C-103

Smallest solution

Sumida CDRH4D28-100

Coilcraft DO1608C-103

High efficiency

0 mA to 300 mA

10

µH

Murata LQH4C100K04

Smallest solution

(1)

Parts are valid for –40°C to 85°C.

For best performance, a low ESR output capacitor is needed. At output voltages greater than 1.8 V, ceramic

output capacitors can be used to show the best performance. Output voltages below 1.8 V require a larger output

capacitor and ESR value to improve the performance and stability of the converter.

Table 2. Capacitor Selection

OUTPUT VOLTAGE RANGE

OUTPUT CAPACITOR

OUTPUT CAPACITOR ESR

1.8 V

≤ VI ≤ 5.5 V

Co ≥ 10 µF

ESR

≤ 120 mΩ

0.8 V

≤ VI < 1.8 V

Co ≥ 47 µF

ESR > 50 m

Ω

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:

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

voltage ripple caused by charge and discharging the output capacitor:

Where the highest output voltage ripple occurs at the highest input voltage VI.

16

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