10 Application and Implementation

Note

Information in the following applications sections is not part of the TI component specification,

and TI does not warrant its accuracy or completeness. TI’s customers are responsible for

determining suitability of components for their purposes, as well as validating and testing their design

implementation to confirm system functionality.

10.1 Application Information

10.1.1 Programming the Output Voltage

The output voltage of the TPS6281x-Q1 is adjustable. The output voltage can be programmed for output

voltages from 0.6 V to 5.5 V using a resistor divider from VOUT to GND. The voltage at the FB pin is regulated

to 600 mV. The value of the output voltage is set by the selection of the resistor divider from Equation 7. TI

recommends to choose resistor values which allow a current of at least 2 µA, meaning the value of R2 must not

exceed 400 kΩ. TI recommends lower resistor values for highest accuracy and most robust design.

1

2

1

OUT

FB

V

R

R

V

×

æ

ö

=

-

ç

÷

è

ø

(7)

10.1.2 External Component Selection

10.1.2.1 Inductor Selection

The TPS6281x-Q1 is designed for a nominal 0.47-µH inductor with a switching frequency of typically 2.25 MHz.

Larger values can be used to achieve a lower inductor current ripple but they can have a negative impact on

efficiency and transient response. Smaller values than 0.47 µH cause a larger inductor current ripple which

causes larger negative inductor current in forced PWM mode at low or no output current. For a higher or

lower nominal switching frequency, the inductance must be changed accordingly. See Recommended Operating

Conditions for details.

The inductor selection is affected by several effects like inductor ripple current, output ripple voltage, PWM-to-

PFM transition point, and efficiency. In addition, the inductor selected has to be rated for appropriate saturation

current and DC resistance (DCR). Equation 8 calculates the maximum inductor current.

2

(max)

(max)

(max)

L

OUT

L

I

I

I

D

+

=

(8)

(max)

1

1

min

OUT

OUT

IN

L

SW

V

V

V

I

L

f

×

æ

ö

-

ç

÷

è

ø

D

=

×

(9)

where

• IL(max) is the maximum inductor current

• ΔIL(max) is the peak-to-peak inductor ripple current

• Lmin is the minimum inductance at the operating point

Table 10-1. Typical Inductors

TYPE

INDUCTANCE

[µH]

CURRENT [A]

(1)

FOR DEVICE

NOMINAL

SWITCHING

FREQUENCY

DIMENSIONS

[LxBxH] mm

MANUFACTURER(2)

XFL4015-471ME

0.47 µH, ±20%

3.5

TPS62813-Q1,

TPS62812-Q1

2.25 MHz

4 × 4 ×1.6

Coilcraft

www.ti.com

TPS62810-Q1, TPS62811-Q1, TPS62812-Q1, TPS62813-Q1

SLVSDU1J – AUGUST 2018 – REVISED MARCH 2023

Copyright © 2023 Texas Instruments Incorporated

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