SBVS254D February 2018 – August 2019 TPS7A05
Devices with this option have an internal pulldown MOSFET that connects a 120-Ω resistor to ground when the device is disabled to actively discharge the output voltage. The active discharge circuit is activated when the device is disabled, in undervoltage lockout (UVLO), or in thermal shutdown.
The discharge time after disabling depends on the output capacitance (COUT) and the load resistance (RL) in parallel with the 120-Ω pulldown resistor. Equation 1 calculates the time constant:
Do not rely on the active discharge circuit for discharging a large amount of output capacitance after the input supply has collapsed because reverse current can flow from the output to the input. This reverse current flow can cause damage to the device. Limit reverse current to no more than 5% of the device-rated current.