BD9415FS Datasheet, PDF (15/34 Pages) Rohm – White LED Driver for 4Ch Large LCD Panels (DC/DC converter type)

BD9415FS
3.2.6 OVP Setting
The OVP terminal is the input for over-voltage protection of output voltage.
The OVP pin is high impedance, because the internal resistance is not connected to a certain bias.
Detection voltage of VOUT is set by dividing resistors R1 and R2. The resistor values can be calculated by the formula
below.
○ OVP Detect Equation
If VOUT is boosted abnormally, VOVPDET, the detect voltage
of OVP, R1, R2 can be expressed by the following formula.
R1  R2[k] ^{VOVPDET [V ]  3.0[V ] } [k]　
3.0[V ]
○ OVP Release Equation
By using R1 and R2 in the above equation, the release voltage
of OVP, VOVPCAN can be expressed as follows.
VOVP_CAN
 2.9[V ] ^{R1[k]  R2[k]}
R2[k]
_　
VOUT
OVP
R1
+
OVP COMP ^{- 3.0V/2.9V}
R2
SCP COMP _-
+ ^0.2V
Figure 17 . OVP setting example
【setting example】
If the normal output voltage, VOUT is 58V, the detect voltage of OVP is 63V, R2 is 20kΩ, R1 is calculated as follows.
R1  R2[k] ^{VOVPDET [V ]  3.0[V ] }  20[k]　 ^{63[V ]  3.0[V ]}  400[k]
3.0[V ]
3.0[V ]
By using these R1 and R2, the release voltage of OVP, VOVPCAN can be calculated as follows.
VOVP_CAN
 2.9[V ] ^{R1[k]  R2[k]}
R2[k]
 _{　 2.9[V ]} 400[k]  20[k] _{ 60.9[V ]}
20[k]
3.2.7 SCP setting
【3.2.6) The SCP setting「VSCPDET」 voltage is calculated as below when R1,R2 is decided above:
VSCP_DET
 0.2[V ]  ^{R1[k]  R2[k]}
R2[k]
 _{　 0.2[V ] } 400[k]  20[k] _{ 40.2[V ]}
20[k]
*Also including the variation in IC, please also take the part variation in a set into consideration for an actual constant
setup, and inquire enough to it.
3.2.8 FAILB Logic
FAILB signal output pin (OPEN DRAIN); when an abnormality is detected, NMOS is brought into GND Level.
The rating of this pin is 20V.
State
In completion of an
abnormality
（After CP count^※）
FAILB output
GND Level
(500ohm (Typ))
In normal state, In STB
OPEN
※CP count ： Count movement after detection of D-S SHORT, LED_OPEN, SHORT, SCP.
www.rohm.com
© 2015 ROHM Co., Ltd. All rights reserved.
TSZ22111・15・001
15/30
TSZ02201-0F2F0C100140-1-2
23.May.2016 Rev.001