L

L

1

VIN

VOUT

FB

C

2

EN

GND

TPS6122x

R

1

R

2

V

IN

C

1

0

20

40

60

80

100

0.7

1.7

2.7

3.7

4.7

V - Input Voltage - V

I

I

= 50 mA

O

I

= 100

A

O

m

I

= 10 mA

O

I

= 1 mA

O

TPS61220, TPS61221, TPS61222

www.ti.com

SLVS776B – JANUARY 2009 – REVISED NOVEMBER 2014

The TPS6122x is not sensitive to the ESR in terms of stability. However, low ESR capacitors, such as ceramic

capacitors, are recommended anyway to minimize output voltage ripple. If heavy load changes are expected,

increase the output capacitor value to avoid output voltage drops during fast load transients.

11.2.1.3 Application Curves

Figure 27 shows the excellent efficiency of the converter, which remains above 80% even with heavily

discharged cells.

Figure 27. TPS61222 Performance

11.2.2 Specific Application, Variable Output Voltage Supply

Figure 28. Application Circuit For Adjustable Output Voltage Option

11.2.2.1 Design Requirements

•

Single 4.2 V output at up to 50 mA

•

Power source, two AA alkaline cells

•

Greater than 80% conversion efficiency

11.2.2.2 Detailed Design Procedure

The design procedure for this application is identical to that for the fixed-output supply except for programming

the output voltage.

11.2.2.2.1

Device Selection

This application example uses the TPS61220 so that the output voltage can be set at 4.2 V.

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Product Folder Links: TPS61220 TPS61221 TPS61222