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PGA4311: stuck with no output after "MAINS SUPPLY incident"

Sebastian Ruhland
Prodigy 45 points
Part Number: PGA4311

Hello,

we are using PGA4311 in a preamplifier project. i stumbled upon a strange behaviour.

preamp is running and music is playing. on the same mains phase a power strip got switched off and preamp stopped playing music. (the microcontroller inside still working, switching inputs etc. i assume the microcontroller also still able to send commands via SPI to the PGA4311 but could not check it.)

After turning device off and on again it is working fine again. i tried (and still try) to reproduce this behaviour but wasn't able to get it to that state again.

Thinking about all of it some questions came up to my mind.

on page 6 in the datasheet "Power-Up State" there is the "power-up reset" described, "...100ms during which the circuit is in hardware MUTE state..."

- Could it somehow be stuck in this state?(assuming the mains supply incident caused a reset)

- What happens if SPI communication occurs during these 100ms?

- is there a limitation how often SPI commands can be send to the PGA4311 per second?

i will try to reproduce this behaviour and then check supply voltages and communication lines with a Mixed Signal Oscilloscope to get more information.

thanks in advance.

  • 0
    TI__Genius 11745 points

    Hi Sebastian,

    You are correct, when the power to the PGA4311 is cycled the device enters into power-up reset, in which the device is in a hardware mute condition for ~100ms.

    Sebastian Ruhland said:
    Could it somehow be stuck in this state?(assuming the mains supply incident caused a reset)

    After the internal reset and calibration (~100ms), the gain setting for all channels is automatically set to 0x00, and therefore all channels are in the software mute condition.

    The gain setting will remain 0x00 until the device receives a command to change the gain.

    Sebastian Ruhland said:
    What happens if SPI communication occurs during these 100ms?

    During the initial 100ms, the device is in a hardware mute condition. The hardware mute cannot be overridden by changing the gain in software and will remain muted.

    Attempting to write to the register during this 100ms will not change the gain, as the gain registers are set to 0x00 anyways after the calibration is complete.

    You will need to wait for the PGA4311 to complete the power-up reset procedure (~100ms) before the gain control is available.

    Sebastian Ruhland said:
    is there a limitation how often SPI commands can be send to the PGA4311 per second?

    The limitation is determined by the timing requirements of the SPI protocol. You may refer to figure 3 and the electrical characteristics section of the PGA4311 datasheet.

    Regards,

    Zach