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Galvanic Isolators

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Replies: 26

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Hi TI team,

We are designing a new product where our product will be interfacing to Industrial machines.

RS485 and CAN are the current requirements

Hence We need to use RS485 transceiver with Isolator and CAN transceiver with Isolator,

So Please let us know whether TI has these parts or not.

Awaiting for your quick response.

Thanks

Manjunath (Hardware Design Engineer)

Crevavi Technologies pvt ltd

  • Manjunath,

    TI does indeed have isolated RS485 and isolated CAN like the ISO1410 and ISO1042 respectively.

    Respectfully,

    Lucas Schulte

  • In reply to Lucas Schulte9:

    Hi Lucas,

    I have updated the CAN and USB isolators in my design and attached is those files.

    Kindly review the circuit and share your comments on this.

  • In reply to Manjunath G14:

    Manjunath,

    You may want to use termination resistors four CAN transceivers. Resistors equal to the characteristic impedance of the line should be used to terminate both ends of the cable to prevent signal reflections. Generally 120ohms is a common value.

    The datasheet also recommends a bulk capacitance of typically 4.7 μF that should be placed near the VCC2 supply pin.

    Also, how are you isolating the DC power supplies?

  • In reply to Lucas Schulte9:

    Hi Lucas,

    I forgot to add Power isolation in my design,

    I was just looking into ISO1042BQDWRQ1  component reference design in TI.com website and found the below one reference design with Power isolation in-it.

    tidrxy2a.pdf

    Below is the functional block diagram of our product.

    If I have to give Power isolation for V, 3.8V and 3.3V supplies, How should I acheive that,

    Please support on this.

  • In reply to Manjunath G14:

    Manjunath,

    Generally we recommend using the SN6505 transformer driver. You could create an isolated 5V supply with it and then use that for Vcc2 of your CAN devices. You can also use LDOs to create your lower voltage supplies from the isolated 5V. Please be sure to implement proper isolation design in your PCB.

    Respectfully,

    Lucas

  • In reply to Lucas Schulte9:

    Hi Lucas,

    In our design we have 3 different power supplies levels : 5V, 3.8V & 3.3V

    Each power supply should be independent to each other? I mean to say, In our design Primary VIN supply is given to 5V and then from 5V we converting to 2 different voltage levels that is 3.3V and 3.8V. 

    SOC uses 3.8V and requires maximum 2.5A of current at robust transmission,

    3.3V components requires 1A at max

    Available transformer driver SN6505 provides only 1A out. So How to isolate 3.8V supply, or Isolation should be given only for CAN and RS485 which is the most effected,

    Request you to make me understand in this case.

    In the attached reference design, The isolated supply is given to VCC1, Please check and confirm

  • In reply to Manjunath G14:

    Manjunath,

    I don't know the complete definition of your system, but you only have to isolate the CAN Vcc2 power if all you need to do is have isolated CAN. The other voltage rails can come from the non-isolated 5V supply in this case. Below is a reference design on how to isolate the CAN transceiver. This same thing will have to happen for isolated RS485 as well. You may be able to use the same isolated 5V rail for your RS485 too depending on your isolation requirements and PCB design constraints.

    Respectfully,

    Lucas

  • In reply to Lucas Schulte9:

    Hi Lucas,

    Thanks understood,

    based on the reference design, I have made a block diagram, Kindly check this.

    I had given individual Power isolation for both RS485 and CAN,( maximum power consumption of RS485 and CAN Isolated transceiver are 75mA*2=150mA and it will vary with respect to datarate, Since TPS76350 IC provides only 150mA output)

    Please check this design.

  • In reply to Manjunath G14:

    and also in the reference design attached, ISOlated supply is given to VCC1, Please check this also.

  • In reply to Manjunath G14:

    Sorry, 150mA is the output current of TPS76350Q