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F28M35 X1 with 1.8V external crystal feeding issue

Benjamin Zhou
Expert 4000 points

Hi Team,

   The customer used 1.9V external OSCILLATOR to feeding X1 in F28M35H52C1, which required 3.3V external oscillator in the latest datasheet.  The customer designed their board at year of 2011 and with the preview datasheet which didn't descripted the 3.3V request.   

   Could you kindly give comments for customer request?

    1) what's the X1 voltage range: recommended and Maximum;

    2) if with 1.9V external oscillator to feeding X1, what's the potential risk? is there any documents has informed the XI external oscillator recommended for voltage level?

Expect for your reply, thanks.

Best Regards/Benjamin

  • 0
    TI__Expert 7885 points
    Hello Benjamin,

    1. Max operating voltage on X1/X2 follows max VDDIO voltage which is 3.63V as these are I/O level pins.

    2. The risk is that the oscillator will not oscillate. Voltage levels VIL/VIH are stated in datasheet in table 5.4 "Electrical Characteristics". Also, I will look into adding a spec specifically for the X1 input level characteristics to this datasheet so that there is no more ambiguity.

    Best Regards,
    Adam Dunhoft
  • 0 in reply to Adam Dunhoft
    TI__Expert 4000 points

    XO32.pdfHi Adam,

     Could you kindly give comments on the risk of using Oscillator customer used which is 1.9V OSC?

  • 0 in reply to Benjamin Zhou
    TI__Expert 7885 points
    Hi Benjamin,

    If the customer is using a 1.9V oscillator, the risk is high. The oscillator which the customer is using will only reach a max of 1.9V. The min requirement for X1 VIH is (0.7 * VDDIO). If VDDIO is at NOM voltage (3.3V), the X1 VIH requirement is 2.31V.

    I cannot completely read the datasheet which you attached and was unable to successfully search for it. Is there an English version? From what I can gather, it is a 3.3V oscillator and matches the VIL/VIH requirements of the F28M35 oscillator.

    Best Regards,
    Adam Dunhoft
  • 0 in reply to Adam Dunhoft
    TI__Expert 4000 points
    Hi Adam,
    Sorry for the XO32 datasheet, I can't find the English version but only with Chinese version, the detailed part number is XO32-YEQTC-20MHz which means it's a 1.8V oscillator.
    I'll discuss with customer for the 3.3V oscillator modification. Noticed with lots of thanks.

    Best Regards
    Benjamin