BD93941EFV Datasheet, PDF (17/30 Pages) Rohm – LED pin rating 60V

BD93941EFV BD93941FP
Datasheet
【Setting Example】
Output voltage=VOUT[V]=56V
LED total current=IOUT[A]=100mA×4ch=0.40A
DCDC input voltage=VIN[V]=14V
DCDC efficiency=η[%]=90%
Total required average input current IIN:
I
IN
[
A]

V_OUT [V ] I_OUT [ A]
V_IN [V ][%]
　
56[V ] 0.40[A]
14[V ]90[%]

1.78
[ A]
When, DCDC switching frequency =fsw[Hz]=200kHz
Inductor L[H]=33uH,
Inductor ripple current ΔIL[A]:
ΔIL

(V_OUT [V ]  V_IN [V ])  V_IN [V ]
L[H ]  V_OUT [V ]  f _SW [Hz ]
　
(56[V ]  14[V ]) 14[V ]
33 10 ^6 [H ]  56[V ]  200 10 ³[Hz ]

1.59
[ A]
Thus, IL peak current Ipeak becomes
Ipeak

I _IN [ A] 
IL[ A] _{[　A]  1.78[ A] } 1.59[ A]
2
2

2.58
…Peak current calculation result
[ A]
RCS resistor value when set at 0.1ohm
VCS _peak  Rcs  Ipeak  0.10[ ]  2.58[ A]  0.258 [V ]  0.45V …RCS resistor consideration
and satisfy the condition.
In addition、OCP detection current I_OCP at this time is
I _OCP

0.45[V ]
0.1[]

4.5
[ A]
If parts used (FET,INDUCTOR、DIODE etc)’s current capacity<5A,
I _peak  I _OCP  ^{Rated current of components}
 2.58[ A]  4.5[ A]  5[ A]
Thus, there is no problem of parts selection as the above condition is satisfied.
In addition、IL ripple current minimum limit Imin is
…DCDC current capacity consideration
Im in

I _IN
[ A]

IL[ A] _{[ A]}
2

1.78[ A]

0.795[ A]

0.985[ A]

0　
Thus、will not become discontinuous mode。
To select DC/DC components, give consideration to IC variations as well as individual component variations, and
then conduct thorough verification on practical systems.
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