BD9489F Datasheet, PDF (31/39 Pages) Rohm – DCDC converter with current mode

BD9489F
3.5.7 LED OCP Detection
Datasheet
STB
PWM
REG58
ISENSE
Abnormal
COUNTOR
SS
GATE
3.0V
3.0V
3.0V
3.0V
Smaller than
4count
4count
3.0V
3.0V
4count
0.4V
DIMOUT
RT ^2.0V
STATE
NORMAL LEDOCP NORMAL _LEDOCP Latch off Reset _{NORMAL LEDOCP}
abnormal
(*1)
(*2)
abnormal
(*3)
(*4) (*5)
(OFF)
(*6)
(*7)
abnormal
(*8)
Latch off
Figure 42. LED OCP Detection
(*1)…If ISENSE>3.0V, LEDOCP is detected, and GATE becomes L. To detect LEDOCP continuously, The DIMOUT is
compulsorily high, regardless of the PWM dimming signal.
(*2)…When the LEDOCP releases within 4 counts of the GATE frequency, the boost operation restarts.
(*3) …As the LEDOCP is detected again, the boost operation is stopped.
(*4)…If the LEDOCP detection continues up to 4 counts of GATE frequency. IC will be latched off.
(*5)…Once IC is latched off, the boost operation doesn't restart even if the LEDOCP releases.
(*6)…The latch off state can be reset by the STB=L.
(*7)…It normally starts by STB=L to H.
(*8)…The operation of the LEDOCP detection is not related to the logic of the PWM.
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TSZ02201-0F1F0C100250-1-2
29.Oct 2014 Rev.002