EP3C16F256I7N Altera, EP3C16F256I7N Datasheet - Page 167

• Manufacturer Part Number: EP3C16F256I7N
• Description: Cyclone III
• Manufacturer: Altera

On-Chip
Termination
Support
Altera Corporation-Preliminary
March 2007
Cyclone III devices feature on-chip termination (OCT) to provide I/O
impedance matching and termination capabilities. On-chip termination
helps to prevent reflections and maintain signal integrity while
minimizing the need for external resistors in high pin-count ball grid
array (BGA) packages. Cyclone III devices provide I/O driver on-chip
impedance matching and on-chip series termination for single-ended
outputs and bidirectional pins.
1
There are two ways to implement on-chip termination in Cyclone III
devices:
■
■
On-Chip Termination With Calibration
Cyclone III devices support on-chip series termination with calibration in
all banks. The on-chip series termination calibration circuit compares the
total impedance of the I/O buffer to the external 25 Ω ±1% or 50 Ω ±1%
resistors connected to the R
I/O buffer impedance until they match (as shown in
shown in
make up the I/O buffer.
Figure 7–7. Cyclone III On-Chip Series Termination With Calibration
OCT with calibration
OCT without calibration
When using on-chip series termination, programmable current
strength is not available.
Figure 7–7
Series Impedance
Cyclone III Driver
is the intrinsic impedance of the transistors that
V
GND
CCIO
UP
R
R
and R
S
S
Cyclone III Device Handbook, Volume 1
DN
pins, and dynamically adjusts the
Z
O
On-Chip Termination Support
Receiving
Figure
Device
7–7). The RS
7–15