Current sensing

Hello Luca,

Our devices can definitely perform in-line current sensing such as you describe. Our best device for this application is the INA240, which has high common-mode rejection at high frequency and can suppress the large common-mode transients in that use case. 

Best regards,

Ian Williams
Applications Manager
Current Sensing

Hi

I know that TI have a lot of component for in-phase current measurement, but my question was regarding some theory and suggestions about shunt sensing to ground. For example I think that ground sensing resistor will sense motor current only when the low side mosfet is on and than should I synchronize conversion to this event? Is there any application that explains ground current sensing?

Regards

Hello Luca,

I see - I misunderstood your question. We have lots of reference material available to discuss low-side sensing. The implementation is very similar to in-line sensing, except for two main differences:

1. The common-mode voltage is lower, typically very close to 0V, so the amplifier Vcm range must support this
2. The common-mode voltage is usually stable, so rejection of input Vcm switching signals is less important

For some assistance with this, please see the following resources:

• A Current Sensing Tutorial
• TI Precision Labs - Current Sense Amplifiers

Best regards,

Ian Williams

Hi

One more question, some TI drivers have the possibility to be commanded in 1xPWM. In this mode what is the meaning of the PWM duty cycle? does it set the motor voltage or current? And the DIR pin?

Regards

Hi

If I use the configuration shown in fig, 62 of the drv8323 datasheet and I use the Hall sensor output for block commutation can I close a current loop using the SOA output? And if I have to make the controller side insulated from the power side I can use digital insulator for logic signals but what about the analog current signal?

Regards

Hi Luca,

As your latest question is related to motor drivers, I've asked our engineers from that group to assist you.

Best regards,

Ian Williams

Luca,

Yes you can use the CSA output to close the current loop, this is how our FOC systems work.

I don't see many customers using isolation on the hall signals as these are already low voltage. Which analog are you trying to isolate?

Regards,

-Adam

Hi Adam

I can feed directly hall signals to the driver input but if I have to close the current loop using the micro PWM generator I have to read the global current monitor CSA in this case to maintain insulation I have to insulate the current signal before read it with the micro A/D.

Regards