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PG

OUT

OUT

7

6

5

IN

IN

EN

GND

3

16

14

13

C1

0.1

µF

PG

10

µF

+

TPS768xx

250 k

Ω

V

O +

V

ref

1 )

R1

R2

where:

(1)

R1 +

V

O

V

ref

* 1

R2

(2)

OUTPUT

VOLTAGE

R1

R2

2.5 V

3.3 V

3.6 V

4.75 V

UNIT

33.2

53.6

61.9

90.8

30.1

30.1

30.1

30.1

k

Ω

k

Ω

k

Ω

k

Ω

OUTPUT VOLTAGE

PROGRAMMING GUIDE

PG

OUT

FB / NC

R1

R2

GND

EN

IN

≤ 0.9 V

≥ 1.7 V

TPS76801

PG

0.1

µF

250 k

Ω

POWER-GOOD INDICATOR

TPS76815Q, TPS76818Q, TPS76825Q

TPS76827Q, TPS76828Q, TPS76830Q

TPS76833Q, TPS76850Q, TPS76801Q

SLVS211J – JUNE 1999 – REVISED OCTOBER 2004

APPLICATION INFORMATION (continued)

Figure 26. Typical Application Circuit (Fixed Versions)

The output voltage of the TPS76801 adjustable regulator is programmed using an external resistor divider as

shown in Figure 27. The output voltage is calculated using:

Resistors R1 and R2 should be chosen for approximately 50-µA divider current. Lower value resistors can be

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

currents at FB increase the output voltage error. The recommended design procedure is to choose R2 = 30.1 k

Ω

to set the divider current at 50 µA and then calculate R1 using:

Figure 27. TPS76801 Adjustable LDO Regulator Programming

The TPS768xx 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. PG does not assert itself when the regulated output voltage falls out of the specified 2%

tolerance, but instead reports an output voltage low, relative to its nominal regulated value.

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