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PCM1803A: Verf1 Voltage

rohollah shirafkan
Prodigy 20 points
Part Number: PCM1803A

Hello,

I searched the topics in the forum and i didn't get my answer completely.

I applied 5V to VCC and 3.3V to VDD and followed the schematic presented in the device datasheet. The inputs are ac-coupled audio signals. when i measure VREF1 by multimeter, the voltage value is around zero!! and VREF2 is around 5V. According to the datasheet, i think VREF1 should be 0.5*VCC = 2.5V. Am i right? if yes, what is the problem?

  • 0
    TI__Guru 57800 points

    Hi, Rohollah,

    Welcome to E2E, Thanks for your interest in our products!.

    The VREF1 pin of PCM1803A is used as the decoupling point for the internal ADC reference, that effectively should be 0.5×VCC. It seems there could be something wrong on your design or with the IC you are using. Can you replicate this behavior with a different board-device combination?. What is the behavior of the digital output of the device?. 

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Prodigy 20 points

    Thank you very much for your reply, Diego.

    I changed the IC and again the same problem. VREF1 is zero. I became curious to measure the current that is drawn from VCC pin. Measured current was 3uA!! I checked the PWDN pin and it was 5V. Here are the measured voltages of other pins:

    BYPAS = 0V, TEST = 0V, OSR = 3.3V, FMT0 = 0V, FMT1=0V, MODE0 = 0V, MODE1 = 0V. The digital interface pins (SCKI, DOUT, BCK, LRCK) are all left unconnected for now.

    According to the datasheet, the current of VCC pin should be 7.7mA. It seems that my ICs are malfunctioned. Am i right?

    Best regards