BD9470AEFV Datasheet, PDF (23/39 Pages) Rohm – White LED driver for medium sized and large sized LCD back light

BD9470AFM・BD9470AEFV
●LED Current setting
Setting of LED output current “ILED” can be made by connecting a resistor RISET to the ISET pin.
RISET and ILED current setting equation
R_ISET
=
3000
I _LED [mA]
[kΩ]　　
However, LED current setting should be made in the range of 40mA to 150mA.
And the setting of ISET resistor is bellow at using 150mA to 250mA.
ILED(mA)
R_ISET = 2653 × ( I _LED[mA] )^−0.9753 [kΩ]　　
150 160 170 180 190 200 210 220
RSET(kohm) 20.00 18.80 17.72 16.76 15.90 15.12 14.42 13.78
230
13.19
240
12.66
250
12.16
○Setting Example
To set ILED current to 100mA, RISET resistance is given by the following equation
R_ISET
=
3000
I _LED [mA]
= ³⁰⁰⁰
100[mA]
= 30
[kΩ]　　
●DC/DC converter drive frequency setting
DC/DC converter drive frequency is determined by making RT resistance setting.
○Drive frequency vs. RT resistance (ideal) equation
R_RT
=
15000
f _SW [kHz]
[kΩ]　
Here fsw = DC/DC converter oscillation frequency
[kHz]
This equation has become an ideal equation without any correction item included.
For accurate frequency settings, thorough verification should be performed on
practical sets.
○Setting example
To set DC/DC drive frequency “fsw” to 200 kHz, RRT is given by the following equation
R_RT
=
15000 ₌ 15000 _{= 75}
f_sw[kHz] 200[kHz]
[kΩ]　　
And , the drive frequency setting range is 100kHz～500kHz.
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TSZ22111・15・001
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TSZ02201-0F10C1002000-1-2
19.Oct.2013 Rev.003