Xilinx Virtex UltraScale+ FPGAs User Manual

Switching Regulator
A switching regulator can provide an ecient means to deliver a well-regulated voltage for the
GTM transceiver analog power supply. Unlike the linear regulator, the switching regulator does
not depend on the voltage drop between the input voltage of the regulator and the output
voltage to provide regulaon. Therefore, the switching regulator can supply large amounts of
current to the load while maintaining high power eciency. It is not uncommon for a switching
regulator to maintain eciencies of 95% or greater. This eciency is not severely impacted by
the voltage drop between the input of the regulator and the output. It is impacted by the load
current in a much lesser degree than that of the linear regulator. Because of the eciency of the
switching regulator, the system does not need to supply as much power to the circuit, and it does
not need to provide a means to dissipate power consumed by the regulator.
The disadvantages to the switching regulator are complexity of the circuit and noise generated
by the regulator switching funcon. Switching regulator circuits are usually more complex than
linear regulator circuits. This shortcoming in switching regulators has recently been addressed by
several switching regulator component vendors. Normally, a switching power supply regulaon
circuit requires a switching transistor element, an inductor, and a capacitor. Depending on the
required eciency and load requirements, a switching regulator circuit might require external
switching transistors and inductors. Besides the component count, these switching regulators
require very careful placement and roung on the printed circuit board to be eecve. Switching
regulators generate signicant noise and therefore usually require addional ltering before the
voltage is delivered to the analog power supply input of the GTM transceiver. Because the
amplitude of the noise should be limited to less than 10 mVpp, the power supply lter should be
designed to aenuate the noise from the switching regulator to meet this requirement.
Power Supply Distribution Network
Die
The decoupling capacitance on the die lters the highest frequency noise components on the
power supplies. The source for this very high frequency noise is the internal on-die circuits.
Package
The UltraScale+ architecture package has addional decoupling. Decoupling capacitors in the
package provide aenuaon for noise in the package power plane, thereby reducing the
interacon between GTM transceiver Duals. These capacitors in the package also aid in
maintaining a low-impedance, high-frequency path between the power supply, MGTAVCC,
MGTVCCAUX, VCCINT_GT or MGTAVTT, and GND.
Chapter 5: Board Design Guidelines
UG581 (v1.0) January 4, 2019 www.xilinx.com
Virtex UltraScale+ GTM Transceivers 128
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Xilinx Virtex UltraScale+ FPGAs Specifications

General

Brand	Xilinx
Model	Virtex UltraScale+ FPGAs
Category	Transceiver
Language	English