lm26480sqx-bf National Semiconductor Corporation, lm26480sqx-bf Datasheet - Page 24

• Manufacturer Part Number: lm26480sqx-bf
• Description: Lm26480 Externally Programmable Dual High-current Step-down Dc/dc And Dual Linear Regulators
• Manufacturer: National Semiconductor Corporation

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FEEDBACK RESISTORS FOR LDOs
The output voltages of the LDOs of the LM26480 are estab-
lished by the feedback resistor dividers R1 and R2 shown on
the application circuit above. The equation for determining
V
the LDOX_FB pin.
The LDO control loop will force the voltage on VFB to be 0.50
V ±3%. The above table shows ideal resistor values to es-
OUT
is: V
Target V
OUT
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3.1
3.2
3.3
3.4
3.5
= V
1
2
3
OUT
FB
(R1+R2)/R2, where VFB is the voltage on
(V)
R1 (KΩ)
1000
1040
1080
1120
1160
1200
200
240
280
320
360
400
440
480
520
560
600
640
680
720
760
800
840
880
920
960
Ideal Resistor Values
R2 (KΩ)
200
200
200
200
200
200
200
200
200
200
200
200
200
200
200
200
200
200
200
200
200
200
200
200
200
200
24
R1 (KΩ)
tablish LDO voltages from 1.0V to 3.5V along with common
resistor values to establish these voltages. Common resistors
do not always produce the target value, error is given in the
final column.
To keep the power consumed by the feedback network low it
is recommended that R2 be established as about 200 KΩ.
Lesser values of R2 are OK at the users discretion..
1100
1150
1210
1000
1000
1000
1210
1210
1210
200
240
280
324
357
402
442
562
604
562
604
715
681
806
845
750
909
Common R Values
R2 (KΩ)
200
200
200
200
200
200
200
232
232
200
200
221
200
226
221
187
215
249
249
255
200
191
187
215
210
200
30040410
Actual V
Com/R (V)
1.393
1.505
1.605
1.711
1.802
1.905
2.118
2.203
2.283
2.412
2.505
2.614
2.709
2.809
2.873
3.118
3.174
3.314
3.381
3.525
1.31
2.01
1.1
1.2
1
3
OUT
W/