BD9479FV ROHM [Rohm], BD9479FV Datasheet - Page 11

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

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© 2012 ROHM Co., Ltd. All rights reserved.
TSZ22111・15・001
BD9479FV
● ● ● ● LED current setting (VREF pin, CLx pin)
● ● ● ● DCDC operation frequency setting (RT Pin)
please be noted that VREF pin input voltage range is (0.6V ～ 3.0V), and decide the
input voltage in normal operation.Basically, if VREF pin voltage is high, it will cause
power dissipation of external PNP Tr become high, so it is preferred to set the VREF pin
voltage lower.
is possible to use resistive divider by setting 82kohm and 18kohm.
so that the voltage of 1/3V(typ.) of VREF voltage.If VREF=0.9V, CLx=0.3V to control
external PNP Tr.Therefore,if 「R
GND, and VREF pin voltage is set as 「V
below.
is possible to change current by setting 「R
The operation frequency of DCDC output is set by resistance which connected to RT pin.
Please decide VREF pin input voltage first.When Analog dimming is performed,
Later, VREF＝0.9V will be set as basic.For example if you create 0.9V from REG50, it
In BD9479FV, the LED current detection is performed by CLx pin.CLx pin is controlled
For current setting, set at each channel.For this reason, in 1ch～4ch and 5ch～8ch, it
○The relationship between operation and RT resistance (ideal)
【 【 【 【 Setting Example】 】 】 】
R
R
CL
RT
[
ohm
f
15000
SW
[
]
kHz
I
]
V
LED
VREF
[
k
[
CL
A
]
」 is set as a resistance which between CLx pin and
[
V
]
]
3
VREF
Above is an ideal equation which do not putted with correction terms。
For accurate frequency setting, please confirm on the real system。
but, the frequency setting range is 100kHz～800kHz。
CL
Here, fsw＝DCDC converter oscillation frequency[kHz]
」value.
」, LED current 「I
Ideal
11/26
LED
」can be calculated as
TSZ02201-0F1F0C100020-1-2
9.Aug.2012 Rev.001
Datasheet