Datasheet

TPS76901, TPS76912, TPS76915, TPS76918, TPS76925
TPS76927, TPS76928, TPS76930, TPS76933, TPS76950
ULTRALOW-POWER 100-mA LOW-DROPOUT LINEAR REGULATORS
SLVS203E – JUNE 1999 – REVISED MAY 2001
13
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
output voltage programming
The output voltage of the TPS76901 adjustable regulator is programmed using an external resistor divider as
shown in Figure 22. The output voltage is calculated using:
V
O
V
ref
1
R1
R2
(1
)
Where:
V
ref
= 1.224 V typ (the internal reference voltage)
Resistors R1 and R2 should be chosen for approximately 7-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 = 169 kΩ to set the divider current at 7 µA and then calculate R1 using:
R1
V
O
V
ref
1 R2
(2)
V
O
V
I
OUT
FB
R2
GND
EN
IN
≤0.9 V
≥1.7 V
TPS76901
1 µF
OUTPUT
VOLTAGE
(V)
R1 R2
2.5
3.3
3.6
4.0
5.0
174
287
324
383
523
169
169
169
169
169
OUTPUT VOLTAGE
PROGRAMMING GUIDE
DIVIDER RESISTANCE
(kΩ)
‡
‡
1% values shown.
3
1
4
2
R1
5
ESR = 0.2 Ω
4.7 µF
Figure 22. TPS76901 Adjustable LDO Regulator Programming