Pad Placement and DC Guidelines
Differential Pad Placement Guidelines
To maintain an acceptable noise level on the V
CCIO
supply, there are
restrictions on placement of single-ended I/O pads in relation to
differential pads in the same I/O bank. Use the following guidelines for
placing single-ended pads with respect to differential pads and for
differential output pads placement in Cyclone II devices.
For the LVDS I/O standard:
■
■
■
■
Single-ended inputs can be no closer than four pads away from an
LVDS I/O pad.
Single-ended outputs can be no closer than five pads away from an
LVDS I/O pad.
Maximum of four 155-MHz (or greater) LVDS output channels per
VCCIO
and ground pair.
Maximum of three 311-MHz (or greater) LVDS output channels per
VCCIO
and ground pair.
For optimal signal integrity at the LVDS input pad, Altera
recommends the LVDS, RSDS and mini-LVDS outputs are
placed five or more pads away from an LVDS input pad.
1
The Quartus II software only checks the first two cases.
For the RSDS and mini-LVDS I/O standards:
■
■
■
Single-ended inputs can be no closer than four pads away from an
RSDS and mini-LVDS output pad.
Single-ended outputs can be no closer than five pads away from an
RSDS and mini-LVDS output pad.
Maximum of three 85-MHz (or greater) RSDS and mini-LVDS output
channels per
VCCIO
and ground pair.
The Quartus II software only checks the first two cases.
For the LVPECL I/O standard:
■
■
Single-ended inputs can be no closer than four pads away from an
LVPECL input pad.
Single-ended outputs can be no closer than five pads away from an
LVPECL input pad.
For optimal signal integrity at the LVPECL input pad, Altera
recommends the LVDS, RSDS and mini-LVDS outputs are
placed five or more pads away from an LVPECL input pad.
1
10–28
Cyclone II Device Handbook, Volume 1
Altera Corporation
February 2008
ALTERA [ ALTERA CORPORATION ]
