TPS73HD301, TPS73HD318, TPS73HD325

DUALOUTPUT LOW DROPOUT VOLTAGE REGULATORS

SLVS167C − SEPTEMBER 1998 − REVISED − MAY 1999

24

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

APPLICATION INFORMATION

programming the adjustable LDO regulator output

Programming the adjustable regulator is done using an external resistor divider as shown in Figure 44. The

equation governing the output voltage is:

V

O +

V

ref

1

) R1

R2

Where

Vref = reference voltage, 1.182 V typ

Resistors R1 and R2 should be chosen for approximately 7-

µA divider current. A recommended value for R2

is 169 k

Ω with R1 adjusted for the desired output voltage. Smaller resistors can be used, but offer no inherent

advantage and consume more power. Larger values of R1 and R2 should be avoided as leakage currents at

FB will introduce an error. Solving for R1 yields a more useful equation for choosing the appropriate resistance:

R1

+

V

O

V

ref

* 1

R2

OUTPUT VOLTAGE

PROGRAMMING GUIDE

VO

1RESET

1OUT

1FB

R1

R2

1GND

1EN

1IN

<0.5 V

>2.7 V

TPS73HD3xx

To System

Reset

0.1

µF

270 k

Ω

+

VI

CSR = 1

Ω

10

µF

OUTPUT

VOLTAGE

R1

R2

1.5 V

1.8 V

2.5 V

3.3 V

3.6 V

4 V

5 V

6.4 V

UNIT

45.3

88.7

191

309

348

402

549

750

169

169

169

169

169

169

169

169

k

Ω

k

Ω

k

Ω

k

Ω

k

Ω

k

Ω

k

Ω

k

Ω

6

5

4

28

24

25

1IN

1OUT

23

3

RESET

VOLTAGE

−†

−†

2.37 V

3.13 V

3.42 V

3.80 V

4.75 V

6.08 V

† Non-operational below 1.9 V

Figure 34. TPS7301 Adjustable LDO Regulator Programming