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Programming the TPS77x01 Adjustable LDO Regulator

V

=V

x(1+)

OUT

ref

R

R

1

2

(1)

V

V

OUT

ref

1)xR

-

2

R =(

1

(2)

IN

EN

GND

FB/NC

OUT

RESET/

PG

RESET orPGOutput

V

OUT

V

IN

0.1 F

m

250kW

TPS77x01

C

OUT

R

1

R

2

> 1.7V

< 0.9V

OUTPUTVOLTAGE

PROGRAMMINGGUIDE

R

1

R

2

UNIT

OUTPUT

VOLTAGE

2.5V

3.3V

3.6V

4.75V

121

196

226

332

110

110

110

110

kW

kW

kW

kW

Reset Indicator

Power-Good Indicator

TPS775xx, TPS776xx

SLVS232I – SEPTEMBER 1999 – REVISED AUGUST 2007

APPLICATION INFORMATION (continued)

The output voltage of the TPS77x01 adjustable regulator is programmed using an external resistor divider as

shown in Figure 25. The output voltage is calculated using Equation 1:

Where:

• V

used, but offer no inherent advantage and waste more power. Higher values should be avoided as leakage

to set the divider current at approximately 10

Figure 25. TPS77x01 Adjustable LDO Regulator Programming

The TPS775xx features a RESET output that can be used to monitor the status of the regulator. The internal

comparator monitors the output voltage: when the output drops to between 92% and 98% of its nominal

regulated value, the RESET output transistor turns on, taking the signal low. The open-drain output requires a

pullup resistor. If not used, it can be left floating. RESET can be used to drive power-on reset circuitry or as a

low-battery indicator. RESET does not assert itself when the regulated output voltage falls outside the specified

The TPS776xx features a power-good (PG) output that can be used to monitor the status of the regulator. The

internal comparator monitors the output voltage: when the output drops to between 92% and 98% of its nominal

regulated value, the PG output transistor turns on, taking the signal low. The open-drain output requires a pullup

resistor. If not used, it can be left floating. PG can be used to drive power-on reset circuitry or used as a

low-battery indicator.

14

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