BD9486F Datasheet, PDF (16/37 Pages) Rohm – 1ch Boost up type White LED Driver for large LCD

BD9486F
【setting example】
Above equation is translated as follows.
RVCC　[Ω] 
VIN　[V]  9　[V]
ICC　[A]  IDCDC　[A]  IREG　[A]
When VIN=12V, ICC=2.0mA, RREG=10kΩand IDCDC=2mA, RVCC’s value is calculated as follows.
RVCC　[] 
12　[V]  9　[V]
 667　[]
0.002　[A]  0.002　[A]  5.0　[V]　1　0000　[]
(ICC is 2.6mA(typ.)) . Please set each values with tolerance and margin.
Datasheet
●3.2.4 LED current setting
LED current can be adjusted by setting the resistance R_S [Ω] which connects to ISENSE pin and ADIM[V].
Relationship between R_S and I_LED current
With DC dimming (ADIM<3.0V)
R_ISENSE

1
3

ADIM[V] _[Ω]
I_LED [ A ]
Without DC dimming (ADIM>3.0V)
R_ISENSE

1.015[V] _[Ω]
I_LED [ A ]
【setting example】
If I_LED current is 200mA and ADIM is 2.0V, we can calculate R_ISENSE as below.
R_ISENSE

1
3

ADIM[V]
I_LED [A]

1
3
2.0[V]
0.2[A]

3.33[Ω]
　
Figure 24. LED current setting example
●3.2.5 DCDC Oscillation Frequency Setting
R_RT which connects to RT pin sets the oscillation frequency f_SW of DCDC.
○Relationship between frequency f_SW and RT resistance (ideal)
R _RT

15000
f_SW [kHz ]
[k  ]　
【setting example】
When DCDC frequency fsw is set to 200kHz, R_RT is as follows.
R_RT

15000
f_sw [kHz]

15000
200[kHz]

75
[k]
　
Figure 25. RT terminal setting example
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13.Feb.2014 Rev.004