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PCM2707C: Three questions about oscillator operation

Hiroaki Masumoto
Expert 1210 points

Part Number: PCM2707C

Dear Support team,

Our customer will use PCM2707C in their application.
Please tell me three questions about the oscillator circuit.
Please refer to attached PDF file.

Questions about oscillator operation
Data Sheet In the equivalent circuit diagram of the oscillator shown in Figure 27, it can be understood that oscillation starts when power is supplied.
However, when they check the waveform using the oscilloscope, oscillation will not start immediately even if VBUS supplies it,
and oscillation will start from the bus reset state.
Question-1 :   Is this oscillation operation correct ?

Question-2 :  Immediately after power up, XTI and XTO both go high level. Is this correct ?

Question-3 :  When D + is open, oscillation started about 3 ms after power supply input. Is this correct ?

Best Regards,
Hiroaki Masumoto

Crystal oscillator.pdf

  • 0
    TI__Guru 57800 points

    Hi, Masumoto-san,

    The figure described from the datasheet is only a simplification from the actual input circuit, so it doesn't reflect all the internal connections. The behavior of the described oscillator operation is correct. XTI and XTO will be at high level, then, the oscillation should start.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Expert 1210 points

    Hi, Diego-san,

    Thank you for your reply.
    I understood that the oscillator is the correct operation.

    I will inform this information to customers.

    Regards,
    Hiroaki Masumoto