BD93942F Datasheet, PDF (14/30 Pages) Rohm – White LED Driver for large LCD Panels (DCDC Converter type)

BD93942F
Datasheet
OVP/SCP Settings
OVP pin is DC/DC output voltage’s over voltage protection and short circuit protection input pin.
OVP pin is a high impedance pin with no pull down resistor. Thus, at OPEN state please set the voltage
input settings using voltage dividing resistor and such.
Respective OVP pin protection conditions are as below
Protection
Name
Detection
Pin
Detection
Condition
Cancellation
Timer
Condition Operations
Protection Type
OVP
SCP
OVP
OVP>3.0V
OVP<2.9V
No
OVP
OVP<0.1V
OVP>0.1V
Yes
DCDC stops during
detection
All latch
○OVP Detection Setting
VOUT abnormally increase、voltage detected by OVP, VOVP_DET,
R1,R2 settings are as follows
R1  R2[k] ^{(VOVPDET[V ]  3.0[V ])} [k]
3.0[V ]
○OVP Cancellation Setting
R1,R2 set from above equation,
OVP cancellation voltage VOVP_CAN equals to
VOVP_CAN

2.9V

(R1[k]  R2[k])
R2[k]
[V ]
Figure 15. OVP/SCP setting example
○SCP Detection Setting
When R1,R2 are set using values obtained above, SCP voltage setting is VSCP_DET is as follows
VSCP_DET

0.1V

(R1[k]  R2[k])
R2[k]
[V ]
【Setting Example】
VOUT at normal operation 56V、OVP detection voltage VOVP_DET=68V、R2=10k, R1 is as follows
R1  R2[k] ^{(VOVPDET [V ]  3.0[V ])} 10[k] ^{(68[V ]  3[V ])}  216.7 [k]
3.0[V ]
3[V ]
When R1, R2 are set at these values, OVP cancellation voltage, VOVP_CAN
VOVP_CAN
 2.9[V ] ^{(R1[k]  R2[k])}
R2[k]
 2.9[V ]^{10[k]  216.7[k]} [V ]　 65.7
10[k]
[V ]
In addition, at this R1, R2, SCP detection voltage
VSCP_DET
 0.1[V ] 
(R1[k]  R2[k])
R2[k]
 0.1[V ]  ^{10[k]  216.7[k][}V ]　 2.27
10[k]
[V ]
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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