BD9489F Datasheet, PDF (18/39 Pages) Rohm – DCDC converter with current mode

BD9489F
Datasheet
(ICC is 2.6mA(typ.)) . Please set each values with tolerance and margin.
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 28. 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 29. RT terminal setting example
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TSZ02201-0F1F0C100250-1-2
29.Oct 2014 Rev.002