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PGA2311 fault with the muting

Matthew Tang
Prodigy 50 points
Other Parts Discussed in Thread: PGA2311, PGA2320, LM3886

Hi,

I've built a serval of the remote volume module with the PGA2311. The power supplied from the Digital/Analog separated regulator with one 7VAC X 2 transformer. So they both D/A also from the same transformer but difference regulators for each part and the ground joined together.

I found that it working quite smooth and almost no noise there. But the mute not function very well all the time. Once I muted it and it never get back. I need to restart everything. This module working with the LM3875 as a passive preamp. Sometime it will mute itself even haven't click the Mute button. I am using the mute function inside the the chip.

I am using the same software and similar layout with the PGA2320 but nothing goes wrong.

I would like to know is it the problem of grounding or just happen in 2311? Should I put the 0.1uf cap between the DGND pin and the ground? What should I do? I built serval piece but problem still there... Please advise! Thanks!

  • 0
    TI__Mastermind 27715 points

    Hello Matthew,

    Sorry to hear that you're experiencing this issue with the mute function of the PGA2311. Can you please provide a full schematic of your PGA2311 circuit so I can verify there are no major issues?

    Best regards,

    Ian Williams
    Linear Applications Engineer
    Precision Analog - Op Amps

  • 0 in reply to Ian Williams
    Prodigy 50 points

    Hi,

    Thanks for your reply. The attachment is the circuit of the PGA2311 part. Looking to hear the advise very soon! Cheers!

  • 0 in reply to Matthew Tang
    TI__Mastermind 27715 points

    Hello Matthew,

    Thank you for posting your schematic. I have some follow-up recommendations and questions for you.

    1. You have very minimal power supply decoupling, other than bulk decoupling (100uF) at the regulator outputs. To provide robustness against transient conditions (such as MUTE), local decoupling at each power pin is required. Please see Figure 5 in the PGA2311 data sheet, where we recommend 10uF and 0.1uF capacitors on VA+, VA-, and VD+. These should be placed right next to their power pins, with the 0.1uF capacitor closest to the pin.
    2. A hardware MUTE function will occur if the power supply rails drop below ±3.2V. Monitor your VA+ and VA- rails when the part gets "stuck" in a MUTE condition. It's possible that there is an issue with your power regulation circuit.
    3. Are you using hardware MUTE (apply a logic low voltage to the MUTE pin) or a software MUTE (write all 00 to the vol. control register)? A software mute, as described on p. 11 of the PGA2311 data sheet, actually shorts the amplifier inputs to AGND. If you have a non-zero voltage at the inputs, you are now driving that voltage directly into GND which can cause overdrive/current limit/thermal issues in your circuit upstream.
    4. Your input circuit is quite complex, with resistor dividers, switches, diodes, transistors, and white boxes which don't have a symbol or description. Can you please describe to me the design of your input circuit? Furthermore, your input circuit doesn't seem to have AC coupling capacitors.  This allows a DC voltage to be present on the PGA2311 input, which can cause clicks or pops when changing gain. You may also try bypassing this input circuit and seeing if the MUTE issue goes away.
    5. You should definitely not connect a capacitor between any ground pin and your PCB GND. This AC-couples your PGA2311 GND from the circuit's GND and will cause problems. Instead, use the power supply decoupling I recommended in #1, and route your analog signal traces away from the digital control lines to prevent unwanted coupling. Using separate grounds for AGND and DGND is not necessary with careful signal routing.

    Best regards,

    Ian Williams

  • 0 in reply to Ian Williams
    Prodigy 50 points

    Hi Ian,

    Thanks for your quick reply.

    1. In fact I do using the 100uF for decoupling. Also I have the 0.1uf directly solder on the power pin of PGA2311

    2. No.... I am using the software one.

    3,4.That means for this issue usually cause by the DC-offset problem from the source? In fact I using the ecap replace the 220R for the input cap. So is it good enough? I think that would be good enough for blocking, right? Or I need to add kind of the network for it? The input network is very simple. The transistor only for driving the relay as the selector.

    5. Got it! But I don't really understand why the PGA2311 will suddenly no sound like muted when it playing for a while. It will get back after I switch it off and on again.

    The output of the PGA2311 connected to the input of the LM3886 through the 330R and after the 330R will have the 22k to ground as load before the input pin of the LM3886...

    Looking forward to the advise soon! Cheers!

    Regards,

    Matthew

  • 0 in reply to Matthew Tang
    TI__Mastermind 27715 points

    Hello Matthew,

    1. On the schematic it looks like you are using 100uF at the output of each regulator. However, you also need local decoupling at each power pin of the PGA2311. This is probably not causing your mute issue, but I highly recommend it for a robust design.
    2. Even if you're using the software mute, when the part gets "stuck" in mute try measuring your VA+ and VA- lines to see if either one is below 3.2V.
    3. Yes, replace the 220 ohm resistor with an AC-coupling cap. That will be good as a first test.

    Best regards,

    Ian Williams

  • 0 in reply to Ian Williams
    Prodigy 50 points

    Hi Ian,

    Thanks for the help.

    The problem happened with the AC coupling e-cap. The e-cap replace to the 220ohm at the day one already! The e-cap is 10uf 16v so I think it is good enough. I will check the voltage on those pins later.

    I would like to know is the PGA2311 usually just took within 100mA for each voltage input? I am using the 10VA 7VACX2 should be good enough for this I think... right? 

    Regards,

    Matthew

  • 0 in reply to Matthew Tang
    TI__Mastermind 27715 points

    Hello Matthew,

    In general, the current on any op amp input pin should not exceed 10mA. Any more current than this is likely to cause damage to the IC.

    Best regards,

    Ian Williams

  • 0 in reply to Ian Williams
    Prodigy 50 points

    Hi Ian,

    I tried to reach the issue of the mute this few days. I found that it just working fine and can mute quite well at the beginning likes first 10 hours. Then if you keep it running after few hours it and trying to mute this. It possibly not coming back again. Then I checked the supply voltage when the issue happened. All are fine (4.95V to VD, 4.95V to VA+ and -5V to VA-). 

    I also found that there will have the very slightly sound like "deeeeeee" when the mute is fault. When it is working fine it will just have a very low volume of the music there... I would like to know what will it be? Thanks!

    Regards,

    Matthew

    PS: The same controller working completely fine with the PGA2320... Thanks!

  • 0 in reply to Matthew Tang
    TI__Mastermind 27715 points

    Hello Matthew,

    A device which works for some time but then fails is often a sign of electrical overstress (EOS). Can you verify that the input and output voltages and input currents of the part are kept within the recommended range given in the PGA2311 data sheet? 

    Best regards,

    Ian Williams