BD9285F ROHM [Rohm], BD9285F Datasheet - Page 20

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

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© 2012 ROHM Co., Ltd. All rights reserved.
TSZ22111・15・001
BD9285F
●3.4.6. how to set OVP, SCP
The OVP terminal is the input for over-voltage protection and short circuit protection of output voltage.
The OVP pin is high impedance, because the internal resistance to a certain bias is not connected.
○ ○ ○ ○ OVP detection equality
○ ○ ○ ○ OVP release equality
○ ○ ○ ○ SCP detection equality
In the same way, the detect voltage of SCP, VSCPdet is
[setting example]
By using these R1, R2, the release voltage of OVP, VOVPcan can be calculated as following.
Moreover, by using these R1, R2 the detect voltage of SCP, VSCPdet is
So, the bias by the external components is required, even if OVP function is not used, because the open connection of
this pin is not fixed the potential.
The resistor value can be calculated by the below formula, if the VOUT voltage is monitored, and that is divided by the
resistor R1, R2 like the below diagram.
If the VOUT is boosted abnormally, VOVPdet is the
detect voltage of OVP, R1, R2 can be expressed by the
following formula.
By using the R1, R2 in the above equality, the release
voltage of OVP, VOVPcan can be expressed as
following.
If the normal output voltage, VOUT is 40V, the detect voltage of OVP is 48V, R2 is 10k ohm, R1 is calculated as
following.
VOVP
VSCP
R
R
VOVP
1
VSCP
1
R
DET
R
CAN
[ 2
CAN
[ 2
DET
k
k
0
2
]
2 .
]
2
9 .
0
V
[ 9 .
V
(
[ 2 .
VOVP
(
V
VOVP
V
(
]
(
R
]
R
[ 1
[ 1
(
DET
k
(
R
k
3
DET
R
R
[ 1
[ 0 .
R
3
[
[ 1
]
[ 2
V
k
]
[ 0 .
[ 2
[
V
k
k
V
R
]
R
k
R
V
]
]
R
[ 2
]
[ 2
]
]
[ 2
3
]
[ 2
k
]
k
[ 0 .
R
k
3
k
R
[ 0 .
[ 2
]
V
])
[ 2
]
k
])
])
V
k
])
[
])
V
[
])
[
V
k
]
]
10
2
]
[ 9 .
0
[
[ 2 .
k
V
V
]
20/36
]
]
10
(
10
48
[
k
[
[
k
V
10
[ 3
]
10
]
[
V
]
k
150
[
OVP
SCP
]
[ 3
k
150
]
V
[
+
-
-
+
]
k
])
[
k
0.2V/0.25V
Figure 27. OVP/SCP setting example
]
[
150
V
]
[
]
V
]
46
[
k
3
4 .
2 .
TSZ02201-0F1F0C100030-1-2
]
[
V
[
OVP
V
]
COVP
]
11.Jul.2012 Rev.001
R1
R2
Datasheet
VOUT