C

4.7

I

F

C

10 uF

O

SW

VIN

EN

VOUT

BP

GND

L

1 H

V

IN

2.65 V .. 4.85 V

V

OUT

5.0 V @ 700mA

TPS61256

TPS61253, TPS61254, TPS61256, TPS61258, TPS61259

SLVSAG8E – SEPTEMBER 2011 – REVISED MARCH 2015

www.ti.com

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. Customers should

validate and test their design implementation to confirm system functionality.

10.1 Application Information

With a wide input voltage range of 2.3 V to 5.5 V, the TPS6125x supports applications powered by Li-Ion

batteries with extended voltage range. Intended for low-power applications, it supports up to 800-mA load current

from a battery discharged as low as 2.65 V and allows the use of low cost chip inductor and capacitors. Different

fixed voltage output versions are available from 3.15 V to 5.0 V. The TPS6125x offers a very small solution size

due to minimum amount of external components. It allows the use of small inductors and input capacitors to

achieve a small solution size. During shutdown, the load is completely disconnected from the battery.

10.2 Typical Application

This section details an application with TPS61256 to output fixed 5.0 V.

Figure 28. Smallest Solution Size Application

10.2.1 Design Requirements

In this example, TPS61256 is used to design a 5-V power supply with up to 700-mA output current capability.

The TPS61256 can be powered by one-cell Li-ion battery, and in this example the input voltage range is from

2.65 V to 4.85 V.

10.2.2 Detailed Design Procedure

Table 3. List of Components

REFERENCE

DESCRIPTION

1.0

μH, 1.8 A, 48 mΩ, 3.2 x 2.5 x 1.0mm max. height

LQM32PN1R0MG0, muRata

1.0

μH, 3.7 A, 37 mΩ, 3.2 x 2.5 x 1.2mm max. height

DFE322512C, TOKO

4.7

μF, 6.3 V, 0402, X5R ceramic

GRM155R60J475M, muRata

10

μF, 6.3 V, 0603, X5R ceramic

GRM188R60J106ME84, muRata

(1)

See Third-Party Products Discalimer

(2)

Inductor used to characterize TPS61254YFF, TPS61255YFF, TPS61256YFF and TPS61257YFF devices.

(3)

Inductor used to characterize TPS61253YFF, TPS61258YFF and TPS61259YFF devices.

10.2.2.1 Inductor Selection

A boost converter normally requires two main passive components for storing energy during the conversion, an

inductor and an output capacitor. It is advisable to select an inductor with a saturation current rating higher than

the possible peak current flowing through the power switches.

The inductor peak current varies as a function of the load, the input and output voltages and can be estimated

using Equation 4.

18

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