AMC1311: Level shifting when using isolated sensors.

kalana de silva

Part Number: AMC1311
Other Parts Discussed in Thread: TINA-TI

Tool/software:

Hi,
I am using AMC1311 for voltage sending in my Dual Active Bridge. Schematics is given below. I am using an isolated 5V to power the left side Vdd1 another isolated 3.3V to power the Vdd2. And the AMC1311 is also isolated. Do I need a level shifter at the output of the sensor that is going to my differential amplifier then to my 3.3V ADC in my MUC?

Or since I am using an isolated 3.3V to power the isolated AMC1311 sensor, level shifting is not necessary here ?

over 1 year ago

0 Alexander Smith over 1 year ago

TI__Guru 61302 points

Hi,

Since the AMC1311 only produces 0-2V differential voltage nominally, the 1.65V level shift is not necessary.

I recommend simulating with TINA-TI which can be found on the product page, or looking at our cookbook circuits here: www.ti.com/.../slyy234.pdf

0 kalana de silva over 1 year ago in reply to Alexander Smith

Prodigy 150 points

Hi Alex,
1.65V is not for level shifting. It is for biasing the signal. Since I am measuring only positive voltage do I need to bias the opamp ?
And what is the rational behind it ?

In some TI reference designs such as the T!-010054 Dual Active Bridge it is biased and in some it is not.
My understanding is if I am measuring only positive voltage and if I calculate the Rsense resistor for the absolute minimum voltage (voltage will not go beyond this point so there is no clipping) I do not need to bias the opamp used with the AMC1311 right ?

+1 Alexander Smith over 1 year ago in reply to kalana de silva

TI__Guru 61302 points

HI Kalana,

Right, so instead of applying 1.65V, you can apply 0V, SIG_GND to this node.

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AMC1311: Level shifting when using isolated sensors.