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AMC1311: Level shifting when using isolated sensors.

kalana de silva
Prodigy 140 points
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 ? 

  • 0
    TI__Guru 55342 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 in reply to Alexander Smith
    Prodigy 140 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 in reply to kalana de silva
    TI__Guru 55342 points

    HI Kalana, 

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