lm27241 National Semiconductor Corporation, lm27241 Datasheet - Page 21

• Manufacturer Part Number: lm27241
• Description: Synchronous Buck Regulator Controller For Mobile Systems
• Manufacturer: National Semiconductor Corporation

Application Information
DESIGN EXAMPLE
V
V
F
BW = = 30kHz
L
L
R
R
C
R
Notice that F-zero due to the R
cross-over frequency (F
quired.
Φ
Pick C
5.6 kΩ
OUT
OUT
BW
IN
OUT
ESR
ESR
OUT
ESR
MAX
= 15V
= 300kHz
= 2.2µH
= 2x100µF Tantalum + 2x47µF Ceramic
= 1.5V
Tantalum = 100mΩ
Ceramic = 15mΩ
total = 13mΩ
total = 294µF
45˚
2
to be 4700pF, and calculate R
F
Z1
<
F
Z2
and F
SW
). TYPE III Compensation is re-
Z1
<
ESR
F
P-COMPLEX
2
. C
is greater than the
2
(Continued)
= 4700 pF, & R
2
=
21
C
C
R
R
Set output voltage:
R
EVALUATION BOARD DETAILS
The Bill of Materials (BOM) is now provided for the LM27241
evaluation board. The schematic is the typical application
circuit. See Layout Guidelines for more guidance on pre-
ferred layout practices and also refer to Application Note
AN-1229. Note that a dual FET pack has been chosen for
the evaluation board.
The evaluation board has its output set to 1.5V. The rated
load 6A continuous, and 7A peak. A minimum load of 0.1mA
should be maintained on each output in SKIP mode, to
ensure regulation.
1
3
3
1
4
= 190p F (use 220pF).
sets F
= 1kΩ
= 5kΩ
= 3.32kΩ
BW
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