MPQ1922 -AEC1 current sensing

Motor Drivers/Sensors
1

Hello,

I am designing a driver stage on a low voltage inverter 80Vdc max with the MPQ1922. I want to measure phase current through the low side fet using the current sense amplifier available on the product. For this I have a few doubts:

  1. As the CSP will be connected to the switching node of the inverter, this pin will have to be protected. In the datasheet you show 2 diodes as protection mechanism but there you depend on the sign of the Vds when the fet is on to polarise the diodes. Plus the smallest Vf for 100V blocking diodes is still big. Do you have any other recommendation? Like an external mosfet connected to the same gate opening the measuring path when LS is on and closing when not
  2. How does the MPQ1922 handles the CSO pin when the LS fet is ON and when it is OFF? When it is OFF does it pull down the output voltage (as the voltage is of no use) or does it continuously amplify the CSP and CSN regardless if the LS is ON or not

Thanks and regards

Diego

2

Hello Diego, welcome to the MPS Forums.

I feel that the evaluation board schematic should provide a better reference for the connections of the MPQ1922 in general:

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To answer you first question, I feel an external FET connected to the same gate opening as the measurement path for the LS FET when it turns on would be good if you are looking to protect this while measuring. Other methods would perhaps be too complex as this is the simplest way I can see you protecting this pin further.

As for the second question, I believe the CSP and CSN pins are continuously amplified to output to the CSO pin as the datasheet doesn’t mention anything else. This of course would be dictated by whether or not the HS or LS FETs are on though if that answers your question?

Hope this provided some insight.

Best,

Krishan