BD9415FS
3.5. Timing Chart
3.5.1 PWM Start Up
7.5V
VCC
2.0V
0.8V
STB
5.8V
REG90
2.5V
UVLO
FAILB
(External PullUp)
SSFB
LED_OK
(internal)
VOUT
PWMx
ILEDx
LED Open Detection
LED Short Detection
OFF
NORMAL
OFF
(*1) (*2) (*3)
(*4)
(*5)
Figure 24. Start Up
(*1)…REG90 starts up when STB is changed from Low to High. In the state where the PWM signal is not inputted, SS terminal
is not charged and DCDC doesn't start to boost, either.
(*2)…When REG90 is more than 5.8V(Typ), the reset signal is released.
(*3)…The charge of the pin SS starts at the positive edge of PWM=L to H, and the soft start starts. The pin SS continues
charging in spite of the assertion of PWM or OVP level.
(*4)…The soft start interval will end if the LED_OK = H (internal signal), By this time, it boosts VOUT to the voltage where the
set LED current flows. The abnormal detection of FBMAX starts to be monitored.
(*5)…As STB=L, the boost operation is stopped instantaneously.( N=L, SSFB=L)
www.rohm.com
TSZ02201-0F2F0C100140-1-2
© 2015 ROHM Co., Ltd. All rights reserved.
21/30
23.May.2016 Rev.001
TSZ22111・15・001
ROHM [ ROHM ]
