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TMS320F28379D-Q1: ADC Signal conditioning and CAN

Prakhar Jain
Prodigy 30 points
Part Number: TMS320F28379D-Q1


Tool/software:

Hi TI's team,

I am developing a custom control card for motor controller. For that I need to sense current. For this I am using LEM's current sensor. The part no. is going to be HC5FW 500-S. Now on checking the data sheet I realized and calculated that the current sensor's output will be in range of 0.5V to 4.5 Volts. I need help regarding few concerns.

1). For cancelling any noise in this signal, I want to use ADC of f28379d in differential mode. So, for that I need to have differential inputs to ADC.  Now regarding this I have a few additional doubts.

a) Will the noise in single ended input be cancelled in ADC if I convert it to a differential signal as I am also converting the noise to differential noise during this process? I think noise in current sensor's output will also become out of phase by 180 degrees after passing through differential amplifier.

b) If yes then how can I convert 0.5V-4.5V single ended signal to a 0-3V differential signal. I know it can be done by a Fully differential amplifier by setting VCOM to 1.5V and gain of the amplifier to be 3/4. Is there any additional protection and circuitry required between FDA and MCU. What is good source to generate 1.5V for VCOM. Can you suggest any part. Also suggesting differential amplifier will be useful. 

c) If no, then what can be done?

2). Now I have another doubt that whether current sensor's output should be isolated from ADC input using some isolation or not? Again, if yes how? 

3) I am planning to put a sallen key filter (low pass). Should it be placed before single ended input (assuming that 1st point is correct and I am converting single ended input to differential for noise cancellation) or should it be placed after differential inputs. Or should I go for a passive low pass filter? 

4) Also, I have a question on CAN. In launchpad CAN ic is non isolated. Should I go for an isolated CAN ic because this CAN will be connected to different parts of vehicle and that may have different grounds. 

As of now these are some of the major concerns.  

Thanks