BD9285F ROHM [Rohm], BD9285F Datasheet - Page 23

• Manufacturer Part Number: BD9285F
• Description: Boost 1channel white LED driver For large LCDs
• Manufacturer: ROHM [Rohm]

www.rohm.com
© 2012 ROHM Co., Ltd. All rights reserved.
TSZ22111・15・001
BD9285F
The DCDC input voltage of the power stage = VIN [V] = 24V
The efficiency of DCDC = η [%] = 90%
The averaged input current IIN is calculated as the following.
And the ripple current of the inductor L ( Δ IL[A]) can be calculated if the switching frequency, fsw = 200kHz, the inductor,
L=100µH.
Therefore the inductor peak current, Ipeak is
If Rcs is assume to be 0.3 ohm
The above condition is met.
And Ipeak_det, the current OCP works is
If the current rating of the used parts is 2A,
This inequality meets the above relationship. The parts selection is proper.
And Imin, the bottom of the IL ripple current can be calculated as following.
This inequality implies the operation is the continuous current mode.
I
peak
Δ
IL
I
VCS
Ipeak
I
IN
I
peak
peak
[
(
A
V
L
_
I
peak
]
[
_
OUT
det
MIN
H
det
V
]
[
I
V
OUT
IN
V
0
Rcs
0
V
]
I
IN
[
[ 5 .
[ 3 .
IN
[
OUT
A
V
[
The current rating
V
V
V
]
[
]
A
]
IN
[
]
Ipeak
]
V
]
[
I
V
]
OUT
IL
. 1
[%]
])
2
[
67
IL
[
f
A
A
SW
2
V
]
[
]
0
A
[
[
IN
[ 3 .
[
A
Hz
]
A
[
[
]
V
40
A
]
24
]
]
]
]
[
V
. 0
[
V
. 1
]
89
. 1
]
100
13
. 1
13
23/36
[
. 0
90
A
13
[
[
48
]
A
A
[%]
[
[
]
10
]
A
A
. 0
(
]
]
40
. 0
. 0
48
6
[
2
[
339
48
. 0
H
V
[
. 1
A
89
[
]
]
67
]
A
]
[
40
24
[
A
. 1
V
[
The current rating confirmation of DCDC parts
A
[
[
]
. 0
V
13
]
V
]
65
]
])
The calculation result of the peak current
[
. 2
0
[
200
A
A
5 .
24
[ 0
]
]
TSZ02201-0F1F0C100030-1-2
V
A
[
V
]
10
]
0
3
[
The Rcs value confirmation
Hz
11.Jul.2012 Rev.001
]
. 0
48
Datasheet
[
A
]