BD9486F Datasheet, PDF (28/37 Pages) Rohm – 1ch Boost up type White LED Driver for large LCD

BD9486F
3.5.6 FBMAX Detection
STB
PWM
Datasheet
REG50
4.0V
4.0V
FB
GATE
CP
SS
・・・・・
・・・・・
①②③ ④
3.0V
3.7V
RT
2.0V
STATE STANDBY
SS
(*1) (*2)
NORMAL
(*3)
CP COUNTOR
STANDBY SS
latch
off
(*4)
(*5) (*6)
(*7)
Figure 37. FBMAX Detection
(*2)…During the soft start, it is not judged to the abnormal state even if the FB=H(FB>4.0V).
(*3)…When the PWM=H and FB=H, the abnormal counter doesn’t start immediately.
(*4)…The CP charge will start if the PWM=H and the FB=H detection continues up to 4 clocks of the GATE frequency. Once the
count starts, only FB level is monitored.
(*5)…When the FBMAX detection continues till the CP charge reaches 3.0V, IC will be latched off. The latch off interval can be
calculated by the external capacitance of CP pin. (Please refer to section 3.2.8.)
(*6)…The latch off state can be reset by the STB=L.
(*7)…It is normally started by PWM=L to H, in this figure.
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13.Feb.2014 Rev.004