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TIDA-00688: Galvanic Isolation Level-How much?

Gaurang Mewada
Prodigy 130 points
Part Number: TIDA-00688
Other Parts Discussed in Thread: LM5017,

We are interested to evaluate this design, it very much matches with our requirement.

Exception is instead of +15,-15V and +5, we need just +24VDC at 40mA

This exception is not that difficult. What I am looking for it is the term Isolation that this design can provide.

What is the isolation between Primary and Secondary in this design?

Additionally, can we get this board for Evaluation?

Our exact requirement is as follows.

Input: 18-36VDC

Output1: 24VDC at 36~40mA at 18VDC Supply

Output2: 24VDC at 36~40mA at 18VDC Supply

 

For Output 2 I am planning to replicate the whole design on the board, i.e. 2 DC-DCs with 2 nos LM5017 and 2 nos planar.

  • 0
    TI__Expert 5130 points
    Guarang, hello and thank you for your interest in Texas Instruments. Your inquiry has been received, however the design owner is currently out of the office. We are looking to determine if we can have your answer provided from another Texas Instruments colleague in our Power Design Services team. Please allow us another 1-2 business days before we are able to respond here.
  • 0
    TI__Prodigy 550 points

    Dear Gaurang,

    Thank you for evaluating this power design.

    The isolation depends exclusively on the PCB parameters. These are given by your own PCB design and by the physical dimensions of the coil. To support your requirements you can remove the negative coil and use the space for the positive coil as well (split it into two halves). The 12 turns for 18V increase to 16 turns for 24 V. Half of it, 8 turns you can put on the layer where the negative voltage was. This results in 8 turns per layer instead of 12. On page 8 of the user guide you can see that the distance from coil to core was 0.475 mm with 12 turns so you gain 1.4 mm when reducing turns from 12 to 8 which you can split between inner and outer core part. Finally you have around1.1 mm distance to the core. Depending on your PCB material you could calculate the isolation voltage. I would assume >1 kV is possible.

    Please also have a look at TIDA-00129. It shows a 24V design with traditional low profile transformer. Here the transformer manufacturer is responsible for the isolation level and can give you the isolation details. Bobbins are available with extended distance for higher isolation voltage (see TIDA-00237).

    Kind regards,

    Ingolf

  • 0 in reply to Ingolf Frank
    Prodigy 130 points

    Hello Ingolf,

    Thank you for clarifications, I understood about winding construction and getting 24V on outputs using 2 layers of PCB.

    For Isolation my question was different, I want to know what is the Isolation level you achieved in TIDA-00688.

    I know it depends upon type of PCB parameters, but I would like to know what was Isolation level for TIDA-00688?

    Thank you

    Regards

  • 0 in reply to Gaurang Mewada
    TI__Prodigy 550 points
    Hello Gaurang,

    We did not measure the isolation level and this data is not available. The intent of the design is to support functional isolation like for eliminating humming loops for analog PLC inputs. It may also support transients if for example a surge pulse causes a voltage difference between primary and secondary side.

    If you need electrical safety this would go beyond the scope of the design. For applications with safety aspects it is important to use a dedicated transformer which has all the required certifications and if needed reinforced isolation.

    Best regards,

    Ingolf
  • 0 in reply to Ingolf Frank
    Prodigy 130 points

    Hello Ingolf

    This answers my question very well.

    Thank you for help.