Original question:
I wanted to experiment the LMP8645HV with a current measurement on a 48V power supply (the LMP8645HV is powered by +12V). When I vary the load the function is correct. However, when I disconnect and reconnect the live load, the LMP8645HV no longer works and is destroyed. Why?
Hello Bernard,
We always appreciate addressing questions on the forum.
I would have to agree with Kai that probing the input lines (+IN/-IN) of the LMP8645HV while you are disconnecting and conecting the load would provide insight on what is happening. There is a possibility that when you connect the live load, there is an instantaneous short from source to ground at the inputs and this is creating a quick enough common-mode (VCM) transient at the inputs which could cause a latch-up internally and destroy internal ESD structures.
Could you provide a schematic? Is the 12V supply separate from the 48V supply? Are there capacitors connected to the inputs of LMP8645HV? Is your load inductive or capacitive? How are defining "destroyed"?
You can try debugging the system by placing 10-Ω resistors in series with +IN and -IN pins to see if this provides some protection in terms of limiting the current into the device. After this you could also place 80V clamping TVS diodes from +IN/-IN to the device GND. See the figure from the INA181 datasheet as an example schematic on doing this. Although, these TVS diodes will only provide protection if the VCM exceed 80V. In the scenario I explained above, it is actually the speed (dVCM/dT) which is possibly causing the damage.
Sincerely,
Peter Iliya
Current Sensing Applications
