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 RS [Ω] which connects to ISENSE pin and ADIM[V].
Relationship between RS and ILED current
With DC dimming (ADIM<3.0V)
RISENSE
1
3
ADIM[V] [Ω]
ILED [ A ]
Without DC dimming (ADIM>3.0V)
RISENSE
1.015[V] [Ω]
ILED [ A ]
【setting example】
If ILED current is 200mA and ADIM is 2.0V, we can calculate RISENSE as below.
RISENSE
1
3
ADIM[V]
ILED [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
RRT which connects to RT pin sets the oscillation frequency fSW of DCDC.
○Relationship between frequency fSW and RT resistance (ideal)
R RT
15000
fSW [kHz ]
[k ]
【setting example】
When DCDC frequency fsw is set to 200kHz, RRT is as follows.
RRT
15000
fsw [kHz]
15000
200[kHz]
75
[k]
Figure 25. RT terminal setting example
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13.Feb.2014 Rev.004