A simply addition of resistor at GATE pin can add the brown in feature to Gen5 CoolSET/controller.
› Concept : The brown in voltage is controlled by the gate and source voltage of the main MOSFET.
Source voltage connects to VCC during startup. Therefore, there is a relationship between VVCC on
and the Vgate which is proportional to Vbus voltage.
› Formula : VBI = Vgate_BI * (RSTARTUP/RBI + 1)
Vgate_BI = VVCC_on + 4V (2V for the internal diode drop and 2V is for the Vgs_on)
› Example : Brown in voltage, Vbus BI = 70V if RSTARTUP=50MΩ, RBI=20MΩ, VVCC on=16V
› Note : The brownout voltage is due to protection e.g. OLP. Therefore, the brown in voltage should
be set higher than lowest bus voltage for OLP. Otherwise, output bouncing still be observed.
› The concept can be applied to both Gen5 FF and QR controller/CoolSET.
