Dose LTM2893 suit AD7983?

Hello everyone

I want to use LTM2893 to isolate SPI I/F for AD7983, is AD7983 compatible with the LTM2893?

On the datasheet of LTM2893, It is mentioned LTM2893 is optimized for isolating 1Msps high resolution 18-bit SAR ADCs, but these are only some suited legacy LTC ADCs on datasheet.

Do you have any recommended legacy ADI ADCs which can work well with LTM2893? 

Best ragards

QI

  • Hello QI,

      The AD4000 family should work with the LTM2893.  I've successfully operated the AD4003 with the LTM2893. The AD4003 is an 18-bit 2Msps SAR.  

      You'll need to operate the AD4003 in the chip-select 3-wire with busy indicator mode and configure the LTM2893 to use a 100MHz SCK2 frequency, 1 word count and a 20-bit word size.  Note that the valid data is in the lower 18-bits.   Here's an example circuit to illustrate the connections between the AD4003 and LTM2893.

    Eric

  • Hello Eric

    Sorry for reply later, Your information is very helpful for me, and thank you very much!!

    best regards

    QI

  • Hi Eric

    Thanks a lot for your information about  AD4003+LTM2893.

    Could you have any information about whether AD7983 is compatible with the LTM2893,  i am considering using AD7983 with LTM2893 because i have used AD7983 in my prototype design.

    and so I checked the following requirements in datesheet for LTM2893.

    ・6.25MHz ≤ SPI shift clock maximum frequency ≤ 100MHz

    ・Operates in SPI mode (0,0): SCK starts low, data captured on rising edge.

    ・Meets setup and hold timing requirements (tHDMISO2 and tSUMISO2) with the SPI shift clock operating between 6.25MHz and 100MHz.

    ・SPI shift clock (SCK) is static outside of CS (the ADC does not require a constant running SCK as a conversion clock) ・If used, the conversion start pulse width minimum is ≤ tCNVH

    and now  i  want to use 50MHz clock for AD7983.

    can  LTM2893 work well with AD7893, Do you have any idea?

    Best ragards

    YQ

  • Hello YQ,

      It might be.   If it is, it will operate in a similar manner as the AD4003 – CS\ mode, 3-wire with busy indicator.  (note that the 47k pull-up resistor shown in fig 28 and 32  of the AD7983 data sheet is too large.  It needs to be closer to the 1k shown in the AD4003 example above.)

      I’ve got an AD7983 on order and will try hooking it and an LTM2893 together on my bench and let you know what I find out.

    Eric

  • Hello Eric

    Thanks for your advice!!

    If you got any information on your bench test, Please let me know. 

    Actually, Now i am using AD7983 in CS/mode,3-wire without busy indicator, As you say, it should be changed.

    Best ragards.

    YQ