9.2.2 Detailed Design Procedure

9.2.2.1 Inductor Selection

The inductor value affects the peak-to-peak ripple current, the PWM-to-PFM transition point, the output voltage

ripple, and the efficiency. The selected inductor has to be rated for its DC resistance and saturation current. The

estimated according to Equation 1.

Equation 2 calculates the maximum inductor current under static load conditions. The saturation current of the

inductor must be rated higher than the maximum inductor current, as calculated with Equation 2. This is

recommended because during a heavy load transient the inductor current rises above the calculated value. A

more conservative way is to select the inductor saturation current according to the high side MOSFET switch

L

Vout

1

Vin

I

= Vout

L

-

D

´

´ ¦

(1)

L

Lmax

outmax

I

I

= I

+

2

D

(2)

where

• f = Switching frequency

• L = Inductor value

Table 9-2 shows a list of possible inductors.

Table 9-2. List of Possible Inductors

INDUCTANCE [µH]

INDUCTOR SERIES

SIZE IMPERIAL

(METRIC)

DIMENSIONS L x W X T

SUPPLIER(1)

0.47

DFE18SAN_G0

0603 (1608)

1.6mm x 0.8mm x 1.0mm max

Murata

0.47

HTEB16080F

0603 (1608)

1.6mm x 0.8mm x 0.6mm max.

Cyntec

0.47

HTET1005FE

0402 (1005)

1.0mm x 0.5mm x 0.65mm max.

Cyntec

0.47

TFM160808ALC

0603 (1608)

1.6mm x 0.8mm x 0.8mm max.

TDK

(1)

See Third-party Products Disclaimer

9.2.2.2 Output Capacitor Selection

The DCS-Control™ scheme of the TPS6286x allows the use of tiny ceramic capacitors. Ceramic capacitors with

low ESR values have the lowest output voltage ripple and are recommended. The output capacitor requires

either an X7R or X5R dielectric. At light load currents, the converter operates in Power Save Mode and the

output voltage ripple is dependent on the output capacitor value. A larger output capacitors can be used

reducing the output voltage ripple.

The inductor and output capacitor together provide a low-pass filter. To simplify this process, Table 9-3 outlines

possible inductor and capacitor value combinations.

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SLUSDU8B – APRIL 2020 – REVISED SEPTEMBER 2020

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