BD9486F Datasheet, PDF (24/37 Pages) Rohm – 1ch Boost up type White LED Driver for large LCD

BD9486F
3.5.2 PWM Start Up 2 (Input STB Signal after Inputted PWM Signal)
Datasheet
Figure 33. PWM Start Up 2 (Input STB Signal after Inputted PWM Signal)
(*1)…REG50 starts up when STB=H.
(*2)…When REG50UVLO releases or PWM is inputted to the edge of PWM=L→H, SS charge starts and soft start period is
started. The GATE pulse outputs only during the corresponding PWM=H. And while the SS is less than 0.4V, the pulse
does not output. The pin SS continues charging in spite of the assertion of PWM or OVP level.
(*3)…The soft start interval will end if the voltage of the pin SS, Vss reaches 3.7V. By this time, it boosts V_OUT to the point where
the set LED current flows. The abnormal detection of FBMAX starts to be monitored.
(*4)…As STB=L, the boost operation is stopped instantaneously (GATE=L, SS=L). (Discharge operation works in the state of
STB=L and REG50UVLO=H. Please refer to section 3.5.3)
(*5)…In this diagram, before the discharge period is completed, STB is changed to High again. As STB=H again, operation will
be the same as the timing of (*1).
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13.Feb.2014 Rev.004