INA185: How to measure the current in Negative voltage circuit

Charlie Xiao

Part Number: INA185

Hi BU expert,

If the Vin is Negative voltage as below, do you have suitable device to recommend? The AVEE and VGL in screen are -6V and -12V. Customer would like to do a overcurrent protect circuit. Thanks.

Regards，

Charlie

over 1 year ago

0 Joe Vanacore over 1 year ago

TI__Genius 15380 points

Hi Charlie,

I would like to clarify your design requirements for the overcurrent protection circuit.

What supply voltages do you have available? Is your input swinging from -12V to -6V? Or are you saying the supplies you have available are negative voltages. I would also like to know if you are measuring current bidirectionally.

Thank you for your post,

Joe

0 Charlie Xiao over 1 year ago in reply to Joe Vanacore

TI__Expert 6590 points

Hi Joe,

Thanks for your support. The voltage are fixed at -6V and -12V. The current is directionally. Do we have suitable solution? Thanks.

Regards,

Charlie

0 Joe Vanacore over 1 year ago in reply to Charlie Xiao

TI__Genius 15380 points

Hi Charlie,

Please be patient with me but I would like to break this down further.

We have an older E2E post where sensing negative voltages was discussed and explained in detail:

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1310108/low-current-sense-negative-voltage--24v

There is also this app note for sensing negative currents and voltages that may help:

–48-V Telecom Current, Voltage, and Power Sense Reference Design

I would recommend going with Peter's recommendations and create a Zener supply for the current sense amplifier.

I hope this helps,

Joe

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INA185: How to measure the current in Negative voltage circuit