OUT

OUT

L max

IN

L max

V

I

I

: =

150 mA continuous current operation

0.8 V

I

: = 300 mA

discontinuous current operation

´

+

´

TPS61291

www.ti.com

SLVSBX9A – SEPTEMBER 2014 – REVISED SEPTEMBER 2014

Typical Application (continued)

Reference

Description

Value

Manufacturer

Low Iq Boost Converter with

TPS61291

Texas Instruments

Bypass Operation

Input capacitor

10µF

Murata

GRM219R61A106KE44D

Output capacitor

22µF

Murata

GRM21BR60J226ME39L

L

Inductor

3.3µH

Coilcraft

LPS3314 3R3

(1)

See the Third-Party Products Disclaimer in the Device Support section.

8.2.2 Detailed Design Procedure

The external components have to fulfill the needs of the application but also the stability criteria of the device's

control loop. The TPS61291 is optimized to work within a range of L and C combinations. The LC output filter

inductance and capacitance must be considered together. The output capacitor sets the corner frequency of the

converter while the inductor creates a Right-Half-Plane-Zero degrading the stability of the converter.

Consequently with a larger inductor a bigger capacitor has to be used to guarantee a stable loop. Table 2 shows

the output filter component selection.

Table 2. Recommended LC Output Filter Combinations

Output voltage

[V]

22

22 + 10

2 x 22

3.3

√

√

3.3 / 3.0

4.7

√

2.2

√

√

√

2.5

3.3

√

(1)

Inductor tolerance and current de-rating is anticipated. The effective inductance can vary by 20% and -30%.

(2)

Capacitance tolerance and bias voltage de-rating is anticipated. The effective capacitance can vary by 20% and -50%.

(3)

This LC combination is the standard value and recommended for most applications.

8.2.2.1 Inductor Selection

The device is optimized to operate with a 3.3µH inductor value. Other inductor values can be used, per Table 2.

inductor needs to be rated for a saturation current which is higher than the switch current limit of typically 1A.

Table 3 lists inductors that have been tested with the TPS61291.

(1)

INDUCTANCE

TYPE

SUPPLIER

3.3

3.3 x 3.3 x 1.3

LPS3314

Coilcraft

3.3

2.95 x 2.95 x 1.4

LPS3015

3.3

3 x 2.5 x 1.5

VLF302515

TDK

3.3

2 x 2 x 1.2

MDMK2020T3R3M

Taiyo Yuden

3.3

2.5 x 2.0 x 1.2

DFE252012

Toko

3.3

3.0 x 3.0 x 1.5

74438335033

Würth

(1)

See the Third-Party Products Disclaimer in the Device Support section.

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