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1.8V Oscillater for AM3874

Michi Yama
Guru 10030 points

Other Parts Discussed in Thread: AM3874

Hi,

Our customer will use 1.8V Oscillator to DEV_OSC input of AM3874. But they can't find any oscillator with 1.8V output.  Could you recommend some oscillator with 1.8V output for AM3874?

They are trying to make an Oscillator. But they can't make it because they don't have soem specification is needed. The needed specification is the below.

* Input capacitance value(pF)

* Accuracy of the frequency - 50ppm , Should it be included the change over the years?

* VIH, VIL value

* The specific condition for Duty min45%, max 45%  -  the spec of voltage level

* Tr, Tf value and specific condition (voltage level 10%, 90% ?)

* Some restricted condition for AM3874.  - 1.8V power supply is input to the both AM3874 and the oscillator at same time. Is this timing allowed by AM3874?

I appreciate your quick reply.

Best regards,

Michi

  • 0
    TI__Guru**** 393215 points
    Hi Michi,
     
    The requirements for the external oscillator are given in the AM387X Datasheet, Section 7.4.5 (Table 7-15 and Figure 7-12).
  • 0 in reply to Biser Gatchev-XID
    Guru 10030 points

    Dear Biser-san,

    Thank you for your reply.

    The requirement in AM3874 datasheet does not satisfy customer' s request.

    Also oscillator is not used on AM3874 evm.  Customer can' find any oscillator with 1.8V output.

    So they requested to make new oscillator to some oscillator manufacture. As you know, making oscillator is required many specification.

    AM3874 datasheet is not enough for customer.

    If you recommend some oscillator with 1.8V output to the customer, it is very helpful.

    Best regards,

    Michi 

  • 0 in reply to Biser Gatchev-XID
    Guru 10030 points

    Dear Biser-san,

    Our customer uses AM3874 with wide temperature range(-40degC to 105degC). So general oscillator can't meet its temperaure spec.

    So please advise me oscillator part number and manufacture name that can operate with AM3874. We must indicate oscillator spec to our customer.

    I appreciate you quick reply.

    Best regards,

    Michi

  • 0 in reply to Biser Gatchev-XID
    Guru 10030 points

    Dear Biser-san,

    Thank you for your support.

    I considered my answer for reference to my customer based on your advising oscillator manufacture.

    Please see the following. If you think therea are some issues, please let me know.

     Input load capacitance (Output load for oscillator) :  15pF ----- from ABRACON data sheet (ASVMB series)

    Ageing : +- 5ppm max 1st year  ----- from ABRACON data sheet (ASVMB series)

    VIH : 0.65 DVDD(min) ----- from AM3874 data sheet

    VIL : 0.35DVDD(max) ----- from AM3874 data sheet

    Pulse duration , DEV_CLKIN high : Min 0.45C (referrence point : Vih MIN) ----- from AM3874 data sheet

    Pulse duration,  DEV_CLKIN low : Max 0.55C(reference point : Vil MAX) ----- from AM3874 data sheet

    Tr, Tf : 7ns(max) ---- from AM3874 data sheet

    Condition of Tr, Tf : CL=15pF, 10%-90%DVDD ----- from ABRACON data sheet (ASVMB series)

    I appreciate your quick reply.

    Best regards,

    Michi

     

    Input

  • 0 in reply to Michi Yama
    TI__Guru**** 393215 points
    Hi Michi-san,
     
    This looks correct to me, if they want to use it as a specification for manufacturing their own oscillator.
  • 0 in reply to Biser Gatchev-XID
    Guru 10030 points

    Dear Biser-san,

    Thank you for your support.

    As you know, I submit the following spec to our customer for 1.8V Oscillator.

     Input load capacitance (Output load for oscillator) :  15pF ----- from ABRACON data sheet (ASVMB series)

    Ageing : +- 5ppm max 1st year  ----- from ABRACON data sheet (ASVMB series)

    VIH : 0.65 DVDD(min) ----- from AM3874 data sheet

    VIL : 0.35DVDD(max) ----- from AM3874 data sheet

    Pulse duration , DEV_CLKIN high : Min 0.45C (referrence point : Vih MIN) ----- from AM3874 data sheet

    Pulse duration,  DEV_CLKIN low : Max 0.55C(reference point : Vil MAX) ----- from AM3874 data sheet

    Tr, Tf : 7ns(max) ---- from AM3874 data sheet

    Condition of Tr, Tf : CL=15pF, 10%-90%DVDD ----- from ABRACON data sheet (ASVMB series)

     

    Today customer asked me again. Please see the following.

    1) Cystal frequecny stability - According to the AM3874 data sheet, it is +-50ppm.  Then I answered to customer about  Ageing : +- 5ppm max 1st year.

    Customer's question is that +-50ppm is included +-5ppm, or not. How do I answer to customer?

    2) I answerd to my customer about pulse duration.

    * Pulse duration , DEV_CLKIN high : Min 0.45C (referrence point : Vih MIN)

    * Pulse duration,  DEV_CLKIN low : Max 0.55C(reference point : Vil MAX)

    Customer would like to know the measure point (voltage level) of pulse duration. May I answer to customer that it is 0.5DVDD level?

    Please advise me again.

    I appreciate your quick reply.

    Best regards,

    Michi

     

  • 0 in reply to Michi Yama
    TI__Guru**** 393215 points
    Hi Michi-san,
     
    1) 50ppm is the maximum allowed. This should include everything.
    2) Yes, midpoint of supply voltage is correct.
  • 0 in reply to Biser Gatchev-XID
    Guru 10030 points

    Dear Biser-san,

    Thank you for your support.

    I have one more request from my customer.

    It is about "the Input load capacitance". I already replied it to customer, it is 15pF.

    I said, "15pF" means that customer can use the oscillator having with 15pF load capacitance.

    But our customer would like to know the real value of the input load capacitance for AM3874.

    Could you advise me about it? 

    Best regards,

    Michi