BD9479FV ROHM [Rohm], BD9479FV Datasheet - Page 16

• 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
● ● ● ● LED short voltage setting(BSx pin, LSP pin)
REG50 voltage.
to approximately 2% or less as a reference.
and R2 comes to 5k .
voltage VLSP will be given by the following equation:
○ ○ ○ ○ LSP setting procedure
【 【 【 【 Setting example】 】 】 】
while LSP pin is in OPEN state.
input (0.3V～3.0V) to LSP pin.
「VLED
The difference is given as:
inside IC.（Refer to upper right schematic）, it
connecting to external resistor.For this reason, when configure the voltage of LSP in resistor divider, it is recommended to
connect a resistor which has a little impact from internal resistance value.（Resistance is less susceptible to internal
resistor, but care must be taken because power consumption will become large.）
Below equation shows how to calculate the detection voltage of VLSP by using R1,R2 resistor divide which connect to
Please set R1 and R2 resistance so that a difference between resistance values found by Equations (1) and (2) will come
Assuming that LSP is approximated by Equation (1) in order to set LSP detection voltage to 5V, R1 comes to
However, this equation is without considering IC resistance. If internal resistance is taken into account, the detection
When calculating LSP detection voltage taking into account internal IC resistance by Equation (2), it will be given as:
The detection voltage of LED short when BSx pin higher than 9V
It is possible to change the LED short detection voltage, please
The
※For the selection of DC/DC components, please also consider the inaccuracy of each componentts.
In addition, because LSP pin has split 3V of terminal resistance
As a result, this setting will be little affected by internal impedance.
VLSP
VLSP
short
V
relationship
LSP
」, and LSP pin voltage 「V
[
V

 


 

(
(
R
45
]
[ 1
VLSP
[
k
k
VLED
between
R
]
]
[ 2
2100
R
k
. 5

 

[ 3
[ 5
REG
028
10
]
k
k
short
[
k
R
LED
]
[
50
]
V
[ 4
]
LSP
[
[
900
k
V
]
R
V
」 as below equation.
]
2
5
]
]
short
[
[ 5
k
(
R
900
R
V
REG
[ 1
4
]
/ ]
k
R
detection
[ 5
[ 2
50
R
[ 5
]
[ 5
V
[ 2
k
V
[
k
]
V
will be combined resistance value of IC’s internal resistance and
R
k
]
]
[ 2
]
2100
]
16/26
]
k
100
R
900
3
R
]
voltage

 

[ 4
[
[ 3
k
REF
k
10
V
. 0
]
]
]
[
56
[
V
V
45
45
R
]
%
]
[ 1
[
[
L
k
k
R
k
) 1 (
[ 1
]
]
k
]
2100
]
R
[ 3
k
[
k
TSZ02201-0F1F0C100020-1-2
]
]

 


 

10
10
[
9.Aug.2012 Rev.001
V
. 5
]
K
028
(
) 2
V
[
V
Datasheet
]
45k