INA225: Behavior at low temperatures

Hello Valued Engineer,

Would you please provide the following additional information:

1. Device bias voltages (input Vcm, V_REF)
2. A basic schematic including any loads at the OUT pin
3. The dynamic system conditions preceding the OUT voltage change and settling. 
   1. Is this a power up condition?
   2. Is the differential input (shunt voltage) changing quickly?
4. Any oscilloscope waveforms showing difference between normal and -20°C behavior would be helpful.

Sincerely,

Peter

Thank you for your comments.

The circuit diagram is shown below.

The oscilloscope waveform is below. I am monitoring the OUT terminal of INA225. As additional information, if 50VSWHOT1 in the circuit diagram is above 49.5V, an event will occur, and if it is below 49.5V, it seems to operate stably even at low temperatures.

This issue occurs during the INA225 startup process. Currently, the circuit is open, so there is no major change in the differential input voltage, and only an inrush current of about 1A flows.

Best regards,

Hello Yuya,

The INA225 has a maximum survivable input Vcm of 40V, yet it is sensing a shunt off a seemingly 50V rail. Could you please clarify if you actually operating the device beyond its limits? If this is the case, then it is not surprising that the output is behaving abnormally, especially over temperature.

Usually when our devices need to operate on busses that exceed its input voltage rating, we recommend floating the 5V supply off the buss, and using the Rz to drop the rest of the voltage. When you do this, you do need to account for how to level shift the output voltage to system ground level.

Sincerely,

Peter