BD9285F Datasheet, PDF (21/39 Pages) Rohm – Boost 1channel white LED driver For large LCDs

BD9285F
Datasheet
●3.4.7. how to set the interval until latch off
BD9285 built in the counter by latch off time, that is performed by counting the oscillation clock which is set by the RT pin.
Since the common oscillation circuit is used for counting, the interval until latch off is corresponding to the 4096 clock,
which the GATE pulse output continuously. Please refer the time chart of the operation from the detect abnormality to the
latch off in the section 3.7.
○latch off time
BD9285 starts the counting up from the detection of each abnormal state, falls to the latch off state when the following
interval has passed.
Only PWM=L input does not reset the timer counter, if the abnormal state continues.
LATCH_TIME
=
2¹²
×
R_RT [Ω]
1.5 ×10¹⁰
=
4096×
R_RT [kΩ]
1.5 ×10⁷
[sec]　
Where LATCHTIME is the interval until latch off state
RRT is the connected resistor of RT pin.
[setting example]
If the resistor of RT pin is 100k ohm, the timer latch interval is as following.
LATCH_TIME
=
4096×
R_RT [kΩ]
1.5×10⁷
=
4096×
100[kΩ]
1.5×10⁷
=
27.3[msec]　
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