Vout

Vin

L

L

L max

out max

1

I

I

Vout

I

I

L

f

2

-

D

D

=

´

=

+

´

C1

R

R1

C

2

2 =

´

TPS62200, TPS62201, TPS62202, TPS62203

TPS62204, TPS62205, TPS62207, TPS62208

SLVS417F – MARCH 2002 – REVISED JUNE 2015

www.ti.com

Typical Application (continued)

•

C1 = upper capacitor of voltage divider.

(5)

For C1 a value should be chosen that comes closest to the calculated result.

where

•

R2 = lower resistor of voltage divider.

•

C2 = lower capacitor of voltage divider.

(6)

For C2 the selected capacitor value should always be selected larger than the calculated result. For example, in

Figure 5 for C2, 100 pF are selected for a calculated result of C2 = 86.17 pF.

If quiescent current is not a key design parameter, C1 and C2 can be omitted, and a low-impedance feedback

divider must be used with R1+R2 <100 k

Ω. This design reduces the noise available on the feedback pin (FB) as

well, but increases the overall quiescent current during operation.

8.2.2.2 Inductor Selection

The TPS6220x device is optimized to operate with a typical inductor value of 10 µH.

For high efficiencies, the inductor should have a low DC resistance to minimize conduction losses. Although the

inductor core material has less effect on efficiency than its DC resistance, an appropriate inductor core material

must be used.

The inductor value determines the inductor ripple current. The larger the inductor value, the smaller the inductor

ripple current, and the lower the conduction losses of the converter. On the other hand, larger inductor values

cause a slower load transient response. Usually the inductor ripple current, as calculated below, is around 20%

of the average output current.

To avoid saturation of the inductor, the inductor should be rated at least for the maximum output current of the

converter plus the inductor ripple current that is calculated as:

where

•

f = switching frequency (1 MHz typical, 650 kHz minimal).

•

L = inductor value.

•

ΔIL = peak-to-peak inductor ripple current.

•

ILmax = maximum inductor current.

(7)

The highest inductor current occurs at maximum Vin.

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

670 mA. Refer to Table 2 for inductor recommendations.

Table 2. Recommended Inductors

INDUCTOR VALUE

COMPONENT SUPPLIER

COMMENTS

10 µH

Sumida CDRH5D28-100

High efficiency

10 µH

Sumida CDRH5D18-100

10 µH

Sumida CDRH4D28-100

10 µH

Coilcraft DO1608-103

6.8 µH

Sumida CDRH3D16-6R8

Smallest solution

10 µH

Sumida CDRH4D18-100

10 µH

Sumida CR32-100

10 µH

Sumida CR43-100

10 µH

Murata LQH4C100K04

12

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