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TMS320F28379D: Reference Design crystal EOL replacement - circuit diagram available?

Chris Yorkey
Genius 15985 points
Part Number: TMS320F28379D
Other Parts Discussed in Thread: LAUNCHXL-F28379D, TMDSCNCD28379D

TI Friends & Family,

Hello all, our TMS320F28379D reference design includes a crystal that has been OBSOLETED. 

 It's replacement recommendation is this:

CTS – 403C11A20M00000 crystal oscillator looks suitable for our application.

 If possible could we please share an alternate recommended circuit diagram for 20MHz, 20PPM crystal oscillator?

The recommended replacement (CTS – 403C11A20M00000) looks to be a suitable alternative.

But we'd like to confirm with a circuit diagram if available/possible.

Let us know if this if available.

 Regards,

Chris

  • 0
    TI__Genius 15385 points

    Hi Chris,

    If you refer to the datasheet under the table "Crystal Oscillator Parameters" you will see the requirements for Crystal Oscillator. As long as they are met, it should be good.

    Best Regards,

    Nirav

  • 0 in reply to Nirav Ginwala
    TI__Genius 15985 points

    Hi Nirav,

    Thank for your quick response.

    From our friendly TI customer "

    I have attached manufacturing part number and crystal oscillator circuit diagram, datasheet shows crystal temp of range is -20C to 70c standard and available -40C to 85C. We require -40C to 85C please let me know it can be used in in our circuit. Please suggest any changes require in the circuit diagram. Please let me know availability of flowing crystal oscillator in future.

    "

    Thanks in advance for your input.

    Regards,

    Chris

  • 0 in reply to Chris Yorkey
    TI__Guru 64510 points

    Chris and I are on the same thread with the customer.
    A question I have about the TMDSCNCD28379D schematic which has a structure similar to the picture on the right; what is the purpose of the resistor from MCU_X1 to OSC_GND?  This does not seem to be consistent with the TMS320F28379D datasheet illustration in Figure 8-8 nor similar to the LAUNCHXL-F28379D schematics.

    If a 1Mohm resistor is to be used, I would have thought it should be across X1 and X2 of the TMS320F28379D, not X1 to GND.

  • 0 in reply to BrandonAzbell
    TI__Expert 5540 points

    Brandon, Chris,

    We have a lot of out of office so this may be delayed.

    We do not require or recommend a 1MOhm resistor there.  I'm not sure where the reference is coming from, so we can't really answer the question from other vendors.

    Best regards,

    Jason

  • 0 in reply to Jason Whiles
    TI__Guru 64510 points

    Thank you, Jason.  I will advise the customer to remove the 1Mohm resistor.

    The reference came from our own EVM board schematic, which admittedly is DNP, on the TMDSCNCD28379D.
    The customer will want to know why we put it there in the first place.

  • 0 in reply to BrandonAzbell
    TI__Mastermind 45426 points

    Hi Brandon,

    BrandonAzbell said:
    The reference came from our own EVM board schematic, which admittedly is DNP, on the TMDSCNCD28379D.
    The customer will want to know why we put it there in the first place.

    The purpose of the DNP resistor is if a user wants to evaluate with the 10MHz internal zero-pin oscillator. In that case they would de-solder the crystal (X1) and populate R24 with a 0 ohm resistor to tie MCU_X1 to VSS (per device datasheet). The resistor is not needed on a production board.

    We recommend customers to consult with crystal vendors to incorporate a crystal that works well with the C2000 device. The crystal vendors can often characterize the board/device with the chosen crystal even.

    Also section 3.6 in https://www.ti.com/lit/spracz9 may be helpful info to you and the customer.

    Best,

    Kevin

  • 0 in reply to Kevin Allen18
    TI__Guru 64510 points

    Thank you, Kevin, for the additional clarification.  This is helpful.