PLLs in Stratix II and Stratix II GX Devices
Figure 1–35. VCCINT Plane Partitioned for VCCA Island
Thick VCCA Trace
Because of board constraints, you may not be able to partition a VCCA
island. Instead, run a thick trace from the power supply to each VCCA pin.
The traces should be at least 20 mils thick.
In each of these three cases, you should filter each VCCA_PLLpin with a
decoupling circuit, as shown in Figure 1–36. Place a ferrite bead that
exhibits high impedance at frequencies of 50 MHz or higher and a 10-F
tantalum parallel capacitor where the power enters the board. Decouple
each VCCA_PLLpin with a 0.1-F and 0.001-F parallel combination of
ceramic capacitors located as close as possible to the Stratix II or
Stratix II GX device. You can connect the GNDA_PLLpins directly to the
same ground plane as the device’s digital ground.
Altera Corporation
July 2009
1–57
Stratix II Device Handbook, Volume 2
ALTERA [ ALTERA CORPORATION ]
