• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 82 subscribers
  • Views 518 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TMS320F2806X Crystal Shunt Capacitance

David Ledger
Prodigy 130 points
Other Parts Discussed in Thread: TMS320F28069

Hello,

I've been looking at the TMS320F28069 and have discovered that it has an almost unachievable specification. This specification is the Shunt capacitance (must be 5pF or less) of the crystal oscillator.
See page 69 of the following datasheet, or CTRL+F the word shunt:

www.ti.com/.../tms320f28069.pdf

I cannot find a single crystal that meets this requirement, is it important, will the ABM2-8.000MHZ-D4Y-T be acceptable (maximum shunt is 7pF).

Kind Regards,

    David Ledger

  • 0
    Guru 192875 points
    Hi David,

    If you check TI's F28069 based controlCard, it has Abracon LLC ABM3B-20.000MHZ-10-1-U-T part (300-8214-1-ND).
    You can refer the datasheet here: www.abracon.com/.../abm3b.pdf

    Your part number should be very well fine!

    Regards,
    Gautam
  • 0 in reply to Gautam Iyer
    TI__Genius 11981 points

    Hi David,

    You are absolutely right, 5pF is too restrictive.  I'll see what can be done to update the DS.  In general I typically say that the DS and errata trump any other document such as user guides, app notes, and even including using TI HW, but in this case I think you'll find relaxing the shunt spec to 7pF should open up a least a few possibliities to you, such as the crystal used on the control card referenced by Gautam.

    I'd also like to point you to this information which contains data from vendors who characterized their crystals with our devices.  F2806x was not specifically done, but several other devices were done which use the same process (F05) and crystal osciallator IP such as F2802x, F281x, and F2833x.

    Since board design and layout impact the crystal startup and performance, we always recommend customers work with crystal vendors on their speecific design and crystal selection.

    I hope you find this information helpful.

    Regards,

    Joe

  • 0 in reply to David Ledger
    Guru 192875 points
    You're Welcome!

    Goodluck & Regards,
    Gautam