Hi Team,
Our customer is trying to replace ACS722LLCTR-40AU-T with TMCS1108A1UQDR, however, there is a problem with zero current output. While the ACS722LLCTR-40AU-T is very stable when there is no current, there is oscillation (over ±1A) or ±60mv when he replaced with TMCS1108A1UQDR. Please see attached schematic diagram from our customer.
Regards,
Danilo
Danilo,
Nothing jumps off the page of the schematic as incorrect. There are a couple things to point here though:
The device will exhibit a small amount of distortion at the lower end of measurement. This is due to the coupling of the noise with the sampling integrator. The sampling integrator updates at 250kHz, so any noise inherent on the signal can cause small oscillations at this frequency to appear on the output like so:
As you can see from the image above, the peak to peak spread correlates roughly to the peak to peak noise values of the device, or roughly 37mVpp.
The schematic of the customer system will not be nearly as important as their layout here. If there are several high current traces in proximity to the board, or any other magnetic based objects exhibiting external fields, these can all have effects on the device, and further worsen the issue. However, if the external devices I mention are in fixed positions, i is possible to mitigate a good majority of their contributions via a one time system level calibration.
