SLAAEQ3 October   2024 AMC7908

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1AMC7908 in PA Biasing
  5. 2Output Features
  6. 3PA Monitoring
  7. 4Power Sequencing
  8. 5Summary
  9. 6References

4 Power Sequencing

Powering the PA on and off in a controlled routine is necessary to prevent the damage to the PA when VDRAIN is applied. If the gate voltage is too high, the PA can operate in saturation mode and cause thermal damage to the PA or the board the PA is mounted on. After the AMC7908 is powered up, the proper start-up sequencing for the PA requires the following steps:

  1. Power on the AMC7908.
  2. Configure the gate voltage to the appropriate pinch-off voltage to keep the PA off.
  3. Enable the VDRAIN voltage.
  4. Now that VDRAIN is applied, the gate bias can be increased to set the desired power output of the PA.
  5. Finally, the RF signal can be enabled. This allows the PA to transmit a signal.

The PA can be safely shut down by reversing the power-on steps:

  1. Disable the RF signal from the PA.
  2. Reduce the DAC outputs to the pinch-off value to turn off the PA.
  3. Disable the VDRAIN voltage.
  4. Disable the DAC outputs after the PA is fully disabled.
  5. Turn off the power to the AMC7908.