Greetings:
I wish to sample a raw 75V 125kHz H-bridge output. The two H outputs will go to a differential amplifer/attenuator to create a single ended, low-level sample of the output voltage. Trouble is, I don't want the raw signals running along my PCB from the high powered department to the low level zone and radiating spikes all over the place. Thus, I'd like to slow the edges just a bit before routing them long distances.
So use an RC. Trouble is, for instance a 1.25MHz cutoff filter with a
500 ohm resistor could potentially dissipate 11.25W in the ressitor on transitions, even though the RMS current is only 17.7mA.The question is, can a simple 0.25W 1210 resistor handle the transients?
If I make the resistors larger, then they contribute to errors in the differential amp gain by being close to its input resistance. Well just make them a part of the input resistors you say? Ok, but then doesn't the AC CMRR suffer if the caps aren't matched?
Looking at the Panasonic ERJ 1% series, they allow only 2.5x rated power for short term overload. But I suspect this isn't really the applicable spec for this situation. There is nothing in the datato help one figure out the device's tolerance to repetitive VERY short term overload, where average power is still well within the continuous rating.
Comments appreciated.
Good day!