Datasheet

  
   
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
ǒ
1 )
R1
R2
Ǔ
Where
V
ref
= 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 kΩ 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 +
ǒ
V
O
V
ref
* 1Ǔ R2
OUTPUT VOLTAGE
PROGRAMMING GUIDE
V
O
1RESET
1OUT
1FB
R1
R2
1GND
1EN
1IN
<0.5 V
>2.7 V
TPS73HD3xx
To System
Reset
0.1 µF
270 kΩ
+
V
I
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
kΩ
kΩ
kΩ
kΩ
kΩ
kΩ
kΩ
kΩ
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