I have a BTS142D "smart" FET low-side switch driving a 12v load, all works great except when the logic (gate) side of the circuit is powered down but the 12v load is powered (Vbb = 12v), it back-feeds through the device (protection circuit presumably), pulls the gate pin (Vin) up to ~5v and turns itself on.
Is this as simple as just adding a stiff enough pull-down resistor to the input or have I missed some design criteria?
The data-sheet / appnotes say nothing about this behaviour.
Best Answer
The data sheets tells you that the on-state input current might be as high as 30 uA. It also tells you that the input threshold voltage for activation might be as low as 0.8 volts (worst case). So, I would naturally want to choose a parallel resistor that was lower than 26.7 kohm. I'd use a 10 kohm pull-down resistor. In the absence of any other information you have to make of the data sheet what you can.
If in doubt, consult the manufacturer.