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ISO1044: DOUBT REGARDING ISOLATION IN IS01044

Jananni Sa
Prodigy 100 points
Part Number: ISO1044
Other Parts Discussed in Thread: ISOW1044

Hi team,

     I hope in ISO1044 there is integrated isolation for both power and signal, then why we need to add separate transformer circuit for power isolation. Whether we need to compulsorily add the transformer circuit or it is okay if we didn't add the transformer circuit and use only the integrated isolation provided in the ic. What is the reason for adding separate transformer circuit for isolation?

With regards,

Jananni Sa

  • 0
    TI__Intellectual 2230 points

    Hi Jananni,

    ISO1044 is without integrated isolation for power. Please use ISOW1044 which is integrated solution for both power and signal. This does not need a separate transformer for isolation. TI's ISOW series have integrated isolated power with signal.

    Thanks

    Vikas J

  • 0 in reply to Vikas Jeevannavar
    Prodigy 100 points

    okay, but in the functional block diagram of ISO1044, it is shown like isolation is there for power. Is this isolation only for signal?

  • 0 in reply to Jananni Sa
    TI__Intellectual 2230 points

    Hi Jananni,

    The functional block diagram is correct. The isolation is for the power supplies, GND and signals. The side 1 and side 2 are completely isolated with a working isolation voltage of 450Vrms. Isolated Interfaces devices need 2 power supplies. ISO1044 needs separate power supplies for side 1(Vcc1) and side 2 (Vcc2). Some applications do not have secondary supply where ISOW1044 is used which has an integrated isolated DC-DC convertor to power side 2 from side 1. 

    Please note that the power supplies for side 1 and side 2 need to be isolated and referenced to GND1 and GND2 respectively. Please share more details on the application to suggest the right product. 

    Thanks
    Vikas J

  • 0 in reply to Vikas Jeevannavar
    Prodigy 100 points

    Hi Vikas,

          Actually, we want to use a CAN FD transceiver with isolated power and signals and CAN open, but we are confused in power isolation part that whether we need to use a transformer circuit or not for ISO series parts because in ISO series parts as per functional diagram VCC1 and VCC2 are isolated. In your previous replies, you have mentioned The isolation is for the power supplies, GND and signals in ISO1044 and ISO1044 is without integrated isolation for power, what is the difference between these two lines. I am not able to understand whether ISO1044 has power isolation or not.

    With Regards,

    Jananni Sa

  • 0 in reply to Jananni Sa
    TI__Intellectual 2230 points

    Hi Jananni,

    Sorry for not being clear in my previous response.

    All our isolation products are completely isolated between side 1 and side 2. This includes the Vcc1 and Vcc2 which are isolated from each other.  The functional block diagram is correct. 

    Since Vcc1 and Vcc2 are isolated, the design would require two power supplies each for side1 and side2. Use of ISO1044 or ISOW1044 depends on the application whether side 2 has a power supply to power the Vcc2 or not. The typical application in ISO1044 shows SN6505 and transformer with LDO on side 2 to power the Vcc2.The SN6505 + transformer + TPS76350 is optional. This is needed if side 2 does not have a power supply or one can use ISOW1044 which has integrated DC-DC convertor with transformer. 

    If the power supplies are available on both sides, then the power supplies can connect to Vcc1 and Vcc2 respectively. There is no need of using SN6505+transformer+TPS76350.

    The connections for ISO1044 will be as mentioned below.



    Vcc1 and Vcc2 supplies are needed for the correct working of ISO1044. The ranges which the supplies can support is mentioned in the datasheet and also in the image above. Please refer to the [FAQ] Can I power the two sides of a digital isolator with different voltages? - Isolation forum - Isolation - TI E2E support forums which holds true for ISO1044.

    Thanks

    Vikas J

  • 0 in reply to Vikas Jeevannavar
    Prodigy 100 points

    Hi Vikas,

    Thank you for your response

    Can we use boost converter instead of transformer circuit for generating 5V for VCC2 or we should use only transformer circuit for generating 5V?

    With Regards,

    Jananni Sa

  • 0 in reply to Jananni Sa
    TI__Intellectual 2230 points

    Hi Jananni,

    If you are generating Vcc2 from side 1 then, you can use any converter which is isolated, transformer circuits provide the isolation needed between the two supplies. Non - isolated boost converters will negate the use of isolation products. To have a robust design, we recommend using the circuits provided in datasheets as they are optimized for the use case.

    Thanks

    Vikas J