When the GTM transceiver’s operating state is changed by either changing the power down state or the reset state, the load current as seen by the on-board power distribution network (PDN) and the power supply regulator is also changed. When the load current changes, the power supply regulator must sense the change in the load current and compensate for this change to maintain the design supply voltage. The effect of a delay in the change in the load current can result in a temporary spike or dip in the power supply voltage. When the operating state of the GTM transceiver goes from power down to power up, the load current transient is positive and the voltage from the regulator might dip while the regulator circuit adapts to the new load conditions. Conversely, when the operating state of the GTM transceiver goes from power up to power down, the load current transient is negative and the voltage from the regulator might spike while the regulator circuit adapts to the new load current conditions.
The magnitude and duration of the voltage transient from the power supply regulator depends upon the design of the power supply regulator circuit. In some cases, the voltage might oscillate as the voltage regulator circuit converges to the design voltage setting.
In all of these cases, the important consideration is that the voltage at the input pin of the device must remain within the operating limits as specified in the Versal ACAP data sheets. Use the Xilinx® Power Estimator (XPE) tool to calculate the amount of power required for the transceivers in your application.