Other Parts Discussed in Thread: LM74680
Tool/software:
Hi,
I am developing a solution that uses the LM74700-EP in a low frequency rectifier circuit. I have a need to bring the anode voltage rapidly to 0V during every half cycle of the already rectified input voltage. According to the timing diagrams in the datasheet there is an initial EN delay of ~80uS. Due to the fact that I will bring the Anode voltage all the way down to 0V during every cycle, I would like to know if this EN delay is independent of the charge on the VCAP. That is to say, does this EN to gate turn on delay timing include the time required to charge the VCAP? If this is the case does this timing in fact include the time required at cold start for the anode to rise above the UVLO threshold, and then if EN is already above EN threshold, the time required to charge the VCAP above VCAP UVLO threshold?
If this is the case if we operate the IC in this rectifier mode, then the voltage on VCAP should be maintained during these short cycle by cycle dips down to 0V on the anode. Does this in fact reduce the EN to gate turn on delay? Or is the EN turn on delay more a function of some internal logic settling within the IC, where this is independent of the conditions on the VCAP pin?
Furthermore, is there a strict requirement for an input capacitor. I understand that most application examples are concerned with automotive reverse current protection and that a TVS combined with an input capacitor makes a great deal of sense. However in my particular application any input capacitance would effect the rest of the circuit I am developing which actually requires the Anode voltage to rapidly follow the rectified source down to its zero crossing point. Is it therefore safe to operate the LM74700-EP without any input capacitance?
All the best
Aidan Walton
