BD9483F 查看數據表（PDF） - ROHM Semiconductor
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BD9483F Datasheet PDF : 32 Pages
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BD9483F,FV
Datasheet
This inequality implies the operation is the continuous current mode.
●3.5.2 Inductor selection
The inductor value affects the input ripple current.
VIN
IL
L
ΔIL
VOUT
ΔIL (VOUT [V] VIN [V]) VIN [V] [A]
L[H] VOUT [V] fSW [Hz]
I IN
VOUT[V] IOUT[A]
VIN[V] η[%]
[A]
Ipeak
I IN [A]
ΔIL[A]
2
[A]
Where
L: the coil inductance [H]
Vout: the DCDC output voltage [V]
Vin: the input voltage [V]
Iout: the output load current (the summation of LED current) [A]
Iin: the input current [A]
Fsw: the oscillation frequency [Hz]
RCS
COUT
Figure 29.
* The current exceeding the rated current value of inductor flown through the coil causes magnetic saturation, results
in decreasing in efficiency. Inductor needs to be selected to have such adequate margin that peak current does not
exceed the rated current value of the inductor.
* To reduce inductor loss and improve efficiency, inductor with low resistance components (DCR, ACR) needs to be
selected
●3.5.3 Output capacitance Cout selection
VIN
IL
L
Output capacitor needs to be selected in consideration of equivalent series
resistance required to even the stable area of output voltage or ripple voltage.
Be aware that set LED current may not be flown due to decrease in LED
terminal voltage if output ripple component is high.
Output ripple voltage VOUT is determined by Equation (4):
VOUT
ΔVOUT
ILMAX R ESR
1
C OUT
I OUT
η
1
f SW
[V] ・・・・・
(4)
RESR
where, RESR is the equivalent series resistance of Cout.
RCS
COUT
Figure 30.
* Rating of capacitor needs to be selected to have adequate margin against output voltage.
* To use an electrolytic capacitor, adequate margin against allowable current is also necessary. Be aware that the
LED current is larger than the set value transitionally in case that LED is provided with PWM dimming especially.
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