lm26484sqx National Semiconductor Corporation, lm26484sqx Datasheet - Page 13

• Manufacturer Part Number: lm26484sqx
• Description: Power Management Unit
• Manufacturer: National Semiconductor Corporation

Component Selection
SW1, SW2 OPERATION
The Buck control loop will force the voltage on V
0.50V.
shows ideal resistor values to establish buck voltages from
0.8V 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 delta column.
V
Target
OUT
0.8
0.9
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
1
2
3
(V)
Ideal Resistor Values
R1/3 (KΩ)
120
160
200
240
280
320
360
400
440
427
463
498
450
480
422
446
471
400
420
440
460
480
500
520
540
560
580
600
R2/4 (KΩ)
TABLE 2. Buck1/2 Configuration and Component Selection Guide
200
200
200
200
200
200
200
200
200
178
178
178
150
150
124
124
124
100
100
100
100
100
100
100
100
100
100
100
R1/3 (KΩ)
Common R Values
121
162
200
240
280
324
357
402
442
432
464
499
453
475
422
442
475
402
422
442
464
475
499
523
536
562
576
604
FB
R2/4 (KΩ)
to be
200
200
200
200
200
200
200
200
200
178
178
178
150
150
124
124
124
100
100
100
100
100
100
100
100
100
100
100
13
Actual V
with Com/R
In addition to the resistor feedback, feedback capacitors are
also required. ( — C3/4/6/8) When choosing the output volt-
age for the two bucks, please take into account the fact that,
the factory has optimized the accuracy of Buck1 at the top
end of the V
V
0.803
0.905
1.393
1.505
1.605
1.713
1.803
1.902
2.083
2.202
2.282
2.415
2.875
2.995
3.115
OUT
1.31
2.01
2.51
2.61
2.71
2.82
3.18
3.31
3.38
3.52
(V)
(V)
1.1
1.2
1
range.
OUT
OUT
Actual V
Delta from
Target (V)
range and Buck2 for the bottom end of the
-0.008
-0.017
-0.018
-0.025
-0.005
0.002
0.005
0.005
0.005
0.013
0.003
0.002
0.002
0.015
0.015
-0.02
-0.02
0.01
0.01
0.01
0.01
0.01
0.02
0.01
0.02
(V)
0
0
0
OUT
C3/6 (pF)
Feedback Capacitors
8.2
8.2
8.2
8.2
8.2
8.2
8.2
8.2
8.2
8.2
8.2
8.2
8.2
8.2
6.8
6.8
6.8
6.8
6.8
6.8
15
15
15
15
12
12
10
10
C4/8 (pF)
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