Multiple ADA2200 demodulating LVDTs, How to drive the primaries?

Hello all,

I am using the reference design in as described in CN0371 where in an ADA2200 is driving an ADG794 switch. The the reference has 2 of the four outputs of the switch dedicated to driving P+ and 2 dedicated to P-.

So here is my question: I need to drive 8 LVDTs, can i drive them from the one switch with the primary coils in parallel or have a dedicated switch for each LVDT?

Thanks in advance,

-Erik

  • Hi,

    I contacted the product owner for your query. He'll get in touch soon.

    Regards,
    Goz

  • Hi Erik,

    You might be able to drive all 8 LVDTs with one switch, but it depends on exactly what you are trying to accomplish.

    I assume you would have an ADA2200 demodulating each of the LVDTs.  The RCLK ouput of one of the ADA2200s would drive a single switch which would drive the 8 LVDTs in parallel.

    This will work if:

    The current drive of the switch can handle the current requirements of the 8 LVDTs. This likely isn't an issue, but you will want to double check.

    The 8 ADA2200s are all clocked from a common clock source so that the CLKIN signal to each of the devices are all at the same frequency.

    You can synchronously reset the ADA2200s, so that they have the same relative phase.  If you rely on the POR of the chip on power-up, the parts will come up in different phases (the RCLKs of the 8 ADA2200s will not be aligned), so this will lead to phase offsets that will need to be corrected.

    Brian

  • Hello Erik

    Were you able to resolve this?

    I am planning to do the exact same thing.

    I am unable to understand whether I need to have 8 ADA2200 devices or 8 ADG794 switches!

    Can you please share some starters?