How do I use the GTZ pins MGTZ_THERM_IN/OUT and MGTZ_SENSE_*?
How do I connect these pins when unused?
The GTZ transceiver provides a thermal diode for die temperature measurements. MGTZ_THERM_IN is the anode and MGTZ_THERM_OUT is the cathode of the thermal diode.
Usually, the cathode is grounded and the temperature is calculated from the voltage measured at MGTZ_THERM_IN.
A precise 100 uA current should be injected in MGTZ_THERM_IN. The measure voltage across the Thermal diode anode and cathode (GND) is also a factor of the device temperature, according to the equation below.
The current must be precisely controlled, otherwise the temperature result changes. The temperature is then calculated from the voltage at MGTZ_THERM_IN:
T = 667.195 - 539.955*V-273
When unused, these pins can be left floating.
In many applications, the GTZ analog voltage supplies have local power supply regulators that provide a final stage of voltage regulation. These regulators should preferably be placed as close as possible to the GTZ power supply pins.
Minimizing the distance between the analog voltage regulators and the GTZ power supply pins reduces the opportunity for noise coupling into the supply after the regulator, and for noise generated by current transients caused by load dynamics.
It is very important to use sense pins and route them differentially back to the power supply for close loop feedback. This will guarantee the voltage regulation at the die and adjust for any IR drop on the path.
Xilinx does not guarantee performance if the pins are not properly used. It is required that MGTZVCCH power is present.
|MGTZ_SENSE_AVCC/MGTZ_SENSE_VCC_300||Sense voltage pin for MGTZAVCC|
|MGTZ_SENSE_AGND||Reference pin for MGTZ_SENSE_AVCC|
|MGTZ_SENSE_VCC||Sense pin for die VCCINT voltage|
|MGTZ_SENSE_VCCH||Sense pin for die MGTZVCCH voltage|
|MGTZ_SENSE_GND||Reference pin for MGTZ_SENSE_VCC and MGTZ_SENSE_VCCH|
|MGTZ_SENSE_VCCL||Sense pin for die MGTZVCCL voltage|
|MGTZ_SENSE_GNDL||Reference pin for MGTZ_SENSE_VCCL|
If voltage regulators do not have a sensing function in them, MGTZ_SENSE_xxxx pins should be connected to their respective power pins.
For example, the MGTZ_SENSE_AVCC pin connected to MGTZAVCC.