I/O Structure
Differential On-Chip Termination
Stratix II devices support internal differential termination with a nominal
resistance value of 100 Ω for LVDS or HyperTransport technology input
receiver buffers. LVPECL input signals (supported on clock pins only)
require an external termination resistor. Differential on-chip termination
is supported across the full range of supported differential data rates as
shown in the DC & Switching Characteristics chapter in volume 1 of the
Stratix II Device Handbook.
f
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For more information on differential on-chip termination, refer to the
High-Speed Differential I/O Interfaces with DPA in Stratix II & Stratix II GX
Devices chapter in volume 2 of the Stratix II Device Handbook or the
Stratix II GX Device Handbook.
For more information on tolerance specifications for differential on-chip
termination, refer to the DC & Switching Characteristics chapter in
volume 1 of the Stratix II Device Handbook.
On-Chip Series Termination Without Calibration
Stratix II devices support driver impedance matching to provide the I/O
driver with controlled output impedance that closely matches the
impedance of the transmission line. As a result, reflections can be
significantly reduced. Stratix II devices support on-chip series
termination for single-ended I/O standards with typical RS values of 25
and 50 Ω. Once matching impedance is selected, current drive strength is
no longer selectable. Table 2–17 shows the list of output standards that
support on-chip series termination without calibration.
On-Chip Series Termination with Calibration
Stratix II devices support on-chip series termination with calibration in
column I/O pins in top and bottom banks. There is one calibration circuit
for the top I/O banks and one circuit for the bottom I/O banks. Each
on-chip series termination calibration circuit compares the total
impedance of each I/O buffer to the external 25- or 50-Ω resistors
connected to the RUPand RDNpins, and dynamically enables or disables
the transistors until they match. Calibration occurs at the end of device
configuration. Once the calibration circuit finds the correct impedance, it
powers down and stops changing the characteristics of the drivers.
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For more information on series on-chip termination supported by
Stratix II devices, refer to the Selectable I/O Standards in Stratix II &
Stratix II GX Devices chapter in volume 2 of the Stratix II Device Handbook
or the Stratix II GX Device Handbook.
2–92
Stratix II Device Handbook, Volume 1
Altera Corporation
May 2007
ALTERA [ ALTERA CORPORATION ]
