EP2S130F1020I4 Datasheet, PDF (764/768 Pages) List of Unclassifed Manufacturers – Stratix II Device Handbook, Volume 1

Electromagnetic Interference (EMI)
Figure 11–35. Board Layout for General-Purpose PLL Ground Islands
PCB
Altera Device
Power and ground
gap width at least
25 to 100 mils
Digital
Ground Plane
Analog
Ground
Plane
Common
Ground Area
If your system shares the same plane between analog and digital power
supplies, there may be unwanted interaction between the two circuit
types. The following suggestions will reduce noise:
■ For equal power distribution, use separate power planes for the
analog (PLL) power supply. Avoid using trace or multiple signal
layers to route the PLL power supply.
■ Use a ground plane next to the PLL power supply plane to reduce
power-generated noise.
■ Place analog and digital components only over their respective
ground planes.
■ Use ferrite beads to isolate the PLL power supply from digital power
supply.
Electromagnetic
Interference
(EMI)
Electromagnetic interference (EMI) is directly proportional to the change
in current or voltage with respect to time. EMI is also directly
proportional to the series inductance of the circuit. Every PCB generates
EMI. Precautions such as minimizing crosstalk, proper grounding, and
proper layer stack-up significantly reduce EMI problems.
Place each signal layer in between the ground plane and power (or
ground) plane. Inductance is directly proportional to the distance an
electric charge has to cover from the source of an electric charge to
ground. As the distance gets shorter, the inductance becomes smaller.
11–28
Stratix II Device Handbook, Volume 2
Altera Corporation
May 2007