We have a requirement to protect the power line against induced voltage from the tailgate motors, which we control through H-Bridge IPDs.
Our idea is to use LM74700 + NMOS, but connecting CATHODE to GND, so that the charge pump can be controlled directly from EN pin (always Vanode-Vcathode>0). Please refer to the attached file:
(Not shown in above schematic, but VB_PWR_L has TVS diode and 100uF aluminum capacitor, we have already verified by simulation that LM74700 max absolute ratings would not be exceeded)
The reason why we need to allow reverse current through the MOSFET is the so called “active braking” case, when PWM is applied on the H-Bridges LSD when user is closing the tailgate manually.
Therefore, we cannot rely on automatic ANODE-CATHODE monitoring for charge pump activation.
Any concern with this implementation?
Thanks!
Br,
Marc
