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TPS5140: Oscillator frequency.

Kengo.Y
Guru 11255 points
Part Number: TPS5140

Hi team,

Could you tell me about the tolerance of the oscillator for TPS5140?

My customer found that the oscillator frequencies different from lot to lot.
They designed it at the 135kHz center, but there were some that were 120kHz.
What are the possible causes of device tolerance, except for the external capacitor?

The datasheet specifies TYP value, but how much variation can be considered?

Sincerely.
Kengo.

  • 0
    TI__Expert 7500 points

    Hi Kengo,

    Please give me one or two days to look for the data. This is an old part.

    Will get back to you once I get the data.

    Thanks,

    Lishuang

  • 0 in reply to Lishuang Zhao
    Guru 11255 points

    Hi Lishuang,

    Thank you for your reply.
    I'll wait for your answer.

    Sincerely.
    Kengo.

  • 0 in reply to Kengo.Y
    TI__Expert 7500 points

    Hi Kengo,

    Sure, I am looking into this.

    Thanks,

    Lishuang

  • 0 in reply to Kengo.Y
    TI__Expert 7500 points

    Hi Kengo,

    I am sorry to tell you that we can't find the production data or ATE test data of this old part. 

    In theory, it uses internal current source to charge and discharge the external capacitor to get a triangle, then compare to below Vos(ch) and Vos(cl) voltage to get the clock pulse. So there are some factors to impact the frequency:

    1. Capacitor variation as you mentioned above.

    2. Vos(ch) and Vos(cl) variation as below.

    3. Comparator propagation delay variation.

    But I can't estimate how much variation it may be.

    One thing you can try that find one board with 135KHz (A) and one board with 120KHz (B), then swap their oscillator capacitor and measure the frequency again. We can exclude the effects of capacitance variation.

    One more question, why you select an old part, TPS5140? Can I know your application request? I want to check whether we have new solutions for your application.

    Thanks,

    Lishuang