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Original question:

TAS5717: TAS5717PHPR - Device appears to be unstable - Adding capacitance to OSC resistor or trace leading to it turns on...

TAS5717: Question about Pin16 resistance

Gabriel Wang1
Genius 4435 points
Part Number: TAS5717

Dear Expert

A batch of 1500 was produced, with a small number of boards, and the audio was intermittent and sometimes silent when the pin16 resistance is 18.2K. Touching this resistor with your hand will produce a reaction, sometimes a sound. I changed the resistance to 16K, and the sound is normal, there will be no intermittent, I would like to understand what is going on.

  • 0
    TI__Intellectual 2345 points

    Hi Gabriel,

         The TAS5717/9 PWM processor contains an internal oscillator to support autodetect of I2S clock rates. This reduces system cost because an external reference is not required. Currently, TI recommends a reference resistor value of 18.2 kΩ (1%). This should be connected between OSC_RES and DVSSO.

        As you mentioned the phenomenon, have you measure the Resistance when it's not connected to the circuit? May it's due to the resistance value error.   

    Thanks!

    Aylin

  • 0 in reply to Aylin Zhang
    Genius 4435 points

    Dear Aylin

    This resistance value is correct. Change the resistance of 18.2K with 1%R resistance value and the sound is still abnormal. Change it to 16K and the sound is normal.

    1. Our product R32 uses 18.2K. Most of the product is normal, but only a small part of the audio is abnormal. 2. The specification of R32 recommends 18K, there is no adjustment range, I use 16K for defective products, no other side effects have been found in the current test. Will it matter later. 3. Is there an internal diagram of IC? Can you analyze the function of this resistance? If there is any news, please reply as soon as possible. We explain to the customer why.

  • 0 in reply to Gabriel Wang1
    TI__Intellectual 2345 points

    Hi Gabriel,

       Do you have check the PWM waveforms under normal and abnormal situation? 

       The OSC_RES (18.2kOhm) resistor is sensitive to capacitance. You can check the layout of customer to confirm whether the issue is probably coupling between OSC_RES pin and the adjacent pin that creating noise on the OSC_RES pin. Attention to more spacing and minimizing the distance between the OSC_RES and adjacent pin.

       In the meanwhile, pls take care of all the GND of customer's board are connected toughly.

       Thanks.

    Aylin Zhang