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AMC7834: Gan bias protection

Michael Adelman
Prodigy 180 points
Part Number: AMC7834

Hello,

Do AMC7834 support of power sequencing/protection when VSS goes high to 0V while Vdrain of the amplifier still exist?

thanks,

  • 0
    TI__Guru 52683 points

    Hi Michael,

    The AMC7834 has a few features for when a supply collapse event occurs.  First, if any of the positive supplies start to collapse, the DAC outputs will clamp to the VSS supply and PA_ON digital output pin will be released.  

    This is also true with an AVSS collapse, unfortunately, that means that the drain voltage will eventually reach 0V.  

    For this reason, the PA_ON pin should be used to disable the VDRAIN supply.  This would disable the VSS to prevent an overcurrent condition.

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    Prodigy 180 points

    Hello Paul,

    thank you for the answer, this helps.

    1. what is the time response of PA_ON when it reached the threshold of AVSS to be switched on?

    2.I would like to manipulate PA_ON in such a way so I can use this mechanism for each closed loop DAC individually and independent with PMOS can you please suggest such a way?

    thanks  

  • 0 in reply to Michael Adelman
    TI__Guru 52683 points

    Hi Michael,

    1. The PA_ON pin will be release (normally active low) within 1ms of an AVSS alarm event.  The PA_ON pin will be asserted low when the user issues a register command to the device.  The PA_ON pin can be configured to be sensitive to alarm events (ALARMIN pin, AVSS and overtemperature alarms, etc.) or to the SLEEP pins/commands.  The PA_ON does not automatically get turned on during a startup event.

    2. There is only one PA_ON pin, so it would be difficult to use it independently for each DAC.  You could consider using the GPIOs to optionally turn off one VDRAIN source at time, then use PA_ON to turn them all off if necessary.  This will require your SPI/I2C master to monitor the alarm states of the AMC7834, as the GPIO pins cannot be configured to act as independent alarm pins.

    Thanks,
    paul