APPLICATION INFORMATION

DESIGN PROCEDURE

Programming the Output Voltage

L

L

1

VIN

VOUT

FB

C

2

EN

GND

TPS6122x

fixedoutputvoltage

C

1

æ

ö

ç

÷

è

ø

OUT

FB

V

R

= R

x

- 1

1

2

V

(1)

L

L

1

VIN

VOUT

FB

C

2

EN

GND

TPS6122x

R

1

R

2

V

IN

C

1

TPS61220

TPS61221

TPS61222

The TPS6122x DC/DC converters are intended for systems powered by a single cell battery to up to three

Alkaline, NiCd or NiMH cells with a typical terminal voltage between 0.7 V and 5.5 V. They can also be used in

systems powered by one-cell Li-Ion or Li-Polymer batteries with a typical voltage between 2.5 V and 4.2 V.

Additionally, any other voltage source with a typical output voltage between 0.7 V and 5.5 V can be used with the

TPS6122x family.

Fixed output voltage versions

At fixed voltage versions, the output voltage is set by a resistor divider internally. The FB pin is used to sense the

output voltage. To configure the fixed output devices properly, the FB pin needs to be connected directly to

VOUT as shown in Figure 24.

Figure 24. Typical Application Circuit for Fixed Output Voltage Option

Adjustable output voltage version

In the adjustable output versions, an external resistor divider is used to adjust the output voltage. The resistor

divider needs to be connected between VOUT, FB and GND as shown in Figure 25. When the output voltage is

regulated properly, the typical voltage value at the FB pin is 500 mV for the adjustable devices. The maximum

recommended value for the output voltage is 5.5 V. The current through the resistive divider should be about 100

times greater than the current into the FB pin. The typical current into the FB pin is 0.01

µA, and the voltage

calculated using Equation 1:

As an example, if an output voltage of 3.3 V is needed, a 1-M

has been selected.

Figure 25. Typical Application Circuit for Adjustable Output Voltage Option

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Product Folder Link(s): TPS61220 TPS61221 TPS61222