BD93942F Datasheet, PDF (15/30 Pages) Rohm – White LED Driver for large LCD Panels (DCDC Converter type)

BD93942F
Datasheet
Timer Latch Time Setting
This IC has a built-in timer latch counter. Timer latch time is set by counting the clock frequency which is
set at the RT pin. After abnormal detection time passes, AUTO timer starts, it let IC auto-restart after constant setting
time.
Timer Latch Time
When various abnormal conditions happen, counting starts from the timing, latch occurs after below time has passed.
Furthermore, even if PWM=L, if abnormal condition continues, timer count will not reset.
LATCH_TIME

2¹²
 ^RRT
1.5 10¹⁰

4096
R_RT [k]
1.5 10⁷
[s]
AUTO_TIME

2¹⁷

R_RT
1.5 10¹⁰
 131072

R_RT [k]
1.5 10⁷
[s]
Here, LATCH_TIME = time until latch condition occurs, AUTO_TIME = auto restart timer’s time
R_RT = Resistor value connected to RT pin
LED1 SHORT Pro.
detect
LED1 SHORT Pro.
release
12V
LED1_Voltage
0.4V
0.4V
Oscllator
(internal IC)
CP COUNTER
I_LED1
Current
AUTO
TIMER
0V
CP COUNT UP
START
CP COUNT UP
END
LED1
LATCH OFF
LOW
131072
count
AUTO
RE-START
Figure 16. Example of LED Short protection timing chart
【Setting Example】
Timer latch time when RT=75kohm
LATCH_TIME
 4096 ^{RRT [k]}
1.510⁷
 4096 ^75[k]
1.510⁷
 0.02[s]　
AUTO_TIME

131072
R_RT [k]
1.510⁷

131072
75[k]
1.510⁷
 0.655[s]　
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TSZ02201-0F5F0C100050-1-2
12.Aug.2015 Rev.002