BD9479FV ROHM [Rohm], BD9479FV Datasheet - Page 22

• Manufacturer Part Number: BD9479FV
• Description: White LED Driver for large LCD Panels (DCDC Converter type)
• Manufacturer: ROHM [Rohm]

www.rohm.com
© 2012 ROHM Co., Ltd. All rights reserved.
TSZ22111・15・001
BD9479FV
● ● ● ●
Phase Compensation Setting Procedure
of output capacitor and output resistor (i.e., LED current) and zero (phase lead) f
ESR.
phase delay ( 90 ) characteristics like the pole, the crossover frequency f
Furthermore, the step-up DC/DC converter includes RHP zero “f
To improve transient response, it is necessary to increase R
a phase margin. To avoid this problem, conduct thorough verification, including variations in external components, on
practical systems.
DC/DC converter application for current mode control includes one each of pole f
i.
ii.
iii.
VIN
R
L
CS
※Even if a ceramic capacitor (R
stable operation.
Find Pole f
Find phase compensation to be inserted to error amplifier.(set f
Find zero used to compensate ESR (R
Here,
C
Here,
R
FB
f
p
FB
2
1
2
C
R
I
p
R
LED
ESR
OUT
gm
and RHP zero f
5
ESR
R
V
＝LED Total current[A],
V
f
FB
OUT
I
OUT
p
4
f
LED
C
1
RHZP
0 .
OUT
gm
C
10
]
[
OUT
F
R
ZRHP
V
4
CS
[
OUT
]
[
S
ESR
Hz
of DC/DC converter.
]
I
of the order of milliohms) for C
LED
1 (
ESR
D
22/26
V
D
) of C
OUT
I
LED
)
V
]
[
OUT
OUT
V
FB1
OUT
(electrolytic capacitor).
f
ZRHP
ZRHP
and reduce C
V
IN
” as the second zero. Since the RHP zero has
C
c
V
should be set to not more than RHP zero.
2
OUT
FB
c
is 1/5 to f
1
OUT
FB1
Z
+
-
L
, it is recommended to insert C
1 (
by the output capacitor and capacitor
2
gm
. However, this improvement reduces
p
I
(phase delay) by CR filer consisting
TSZ02201-0F1F0C100020-1-2
ZRHP
LED
D
R
)
1
2
)
FB
]
[
1
Hz
FB
R
C
FB1
FB1
9.Aug.2012 Rev.001
f
p
]
[
F
C
Datasheet
FB2
FB2
for