Datasheet

LM26480
0.47 µF
10 µF
LDO
LDO_FB
Buck
Buck_FB
C1
C2
R1
R2
R1
R2
Using the Evaluation Board www.ti.com
6.3 Component Selection for LDO1 and LDO2
Table 2 shows ideal resistor values to establish LDO voltages from 1.0 V to 3.5 V 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.
Table 2. Component Values for LDO1 and LDO2
Target V
OUT
(V) Ideal Resistor Values Common R Values Actual V
OUT
W/Com/R (V)
R1 (KΩ) R2 (KΩ) R1 (KΩ) R2 (KΩ)
1 200 200 200 200 1
1.1 240 200 240 200 1.1
1.2 280 200 280 200 1.2
1.3 320 200 324 200 1.31
1.4 360 200 357 200 1.393
1.5 400 200 402 200 1.505
1.6 440 200 442 200 1.605
1.7 480 200 562 232 1.711
1.8 520 200 604 232 1.802
1.9 560 200 562 200 1.905
2 600 200 604 200 2.01
2.1 640 200 715 221 2.118
2.2 680 200 681 200 2.203
2.3 720 200 806 226 2.283
2.4 760 200 845 221 2.412
2.5 800 200 750 187 2.505
2.6 840 200 909 215 2.614
2.7 880 200 1100 249 2.709
2.8 920 200 1150 249 2.809
2.9 960 200 1210 255 2.873
3 1000 200 1000 200 3
3.1 1040 200 1000 191 3.118
3.2 1080 200 1000 187 3.174
3.3 1120 200 1210 215 3.314
3.4 1160 200 1210 210 3.381
3.5 1200 200 1210 200 3.525
The output voltages of the LDOs of the LM26480 are established by the feedback resistor dividers R1 and
R2 shown on Figure 5.
The equation for determining V
OUT
is:
V
OUT
= V
FB
× (R1+R2)/R2, where V
FB
is the voltage on the LDO_FB
X
pin.
The LDO control loop will force V
FB
to be 0.50V ±3%.
Figure 5. Feedback Network for Bucks and LDOs
6
AN-1800 Evaluation Kit for LM26480 - Dual DC/DC Buck Regulators with SNVA329D–March 2008–Revised April 2013
Dual Low-Noise Linear Regulators
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