PIFE32251B-R47MS datasheet(78/96 Pages) TI1

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OUT

L(MAX)

OUT(MAX)

)

OUT

OUT(MAX)

IND

)

TPS65094

SWCS133C – SEPTEMBER 2015 – REVISED FEBRUARY 2019

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Application and Implementation

7.2.2.2.1 Selecting the Inductor

An inductor must be placed between the external FETs and the output capacitors. Together, the inductor

and output capacitors form a double-pole in the control loop that contributes to stability. In addition, the

inductor is responsible for the output ripple, efficiency, and transient performance. When the inductance

increases, the ripple current decreases, which typically results in an increase in efficiency. However, with

an increase in inductance, the transient performance decreases. Finally, the inductor selected must be

rated for appropriate saturation current, core losses, and DCR.

NOTE

Internal parameters for the converters are optimized for a 0.47-µH inductor; however, it is

possible to use other inductor values as long as they are chosen carefully and thoroughly

tested.

Equation 5 shows the calculation for the recommended inductance for the converter.

where

•

VOUT is the typical output voltage.

•

VIN is the typical input voltage.

•

fSW is the typical switching frequency.

•

IOUT(MAX) is the maximum load current.

•

KIND is the ratio of ILripple to the IOUT(MAX). For this application, TI recommends that KIND is set to a value

from 0.2 to 0.4.

(5)

With the chosen inductance value and the peak current for the inductor in steady state operation, IL(MAX)

can be calculated using Equation 6. The rated saturation current of the inductor must be higher than the

IL(MAX) current.

(6)

Following these equations, Table 7-2 lists the preferred inductor selected for the converters.

Table 7-2. Recommended Inductors

MANUFACTURER

PART NUMBER

VALUE

SIZE

HEIGHT

Cyntec

PIFE32251B-R47MS

0.47 µH

3.2 mm × 2.5 mm

1.2 mm

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