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AN209

Using Terminator Technology in Stratix & Stratix GX Devices

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AN 209: Using Terminator Technology in Stratix & Stratix GX Devices

How Terminator

Technology

Works

Series

Termination

Resistor (RS)

Two external precision resistors (RUP and RDN) per VCCIO bank are used

as reference resistors. RUP is a pull-up resistor connected to VCCIO; RDN is

a pull-down resistor connected to GND. Terminator technology monitors

the value of the two reference resistors and uses the value to adjust

internal termination circuitry to the same impedance. In addition,

Terminator technology circuitry compensates for voltage, temperature,

and process variation. This circuitry continuously calibrates the internal

termination resistors during normal device operation.

Terminator technology supports one type of I/O standard per I/O bank.

You can enable or disable on-chip termination within an I/O bank on a

pin-by-pin basis. To use different on-chip termination I/O standards on a

device, select separate I/O banks. For example, if you want to use on-chip

termination for GTL+ (3.3-V VCCIO) and SSTL-3 class II (3.3-V VCCIO), use

two separate I/O banks.

Different I/O standards need different VCCIO and VREF voltages. You can

simultaneously use some I/O standards with the same VCCIO in an I/O

bank. For more information, refer to AN 201: Using Selectable I/O Standards

in Stratix Devices.

Terminator technology provides an on-chip series termination resistor

(RS) for single-ended voltage-referenced I/O standard such as SSTL-2 and

SSTL-3. The series termination value for these I/O standards is 25 Ω; the

impedance matching value for these I/O standards is either 25 or 50 Ω. All

I/O pins in Stratix and Stratix GX devices support this termination

method. Table 1 shows the I/O standards supported for series

termination and impedance matching.

Table 1. Supported I/O Standards for Series Termination & Impedance Matching

Feature

Series Termination

Impedance Matching

Supported I/O Standards

SSTL-3 class I

SSTL-3 class II

SSTL-2 class I

SSTL-2 class II

LVTTL/LVCMOS

LVTTL/LVCMOS

LVTTL/LVCMOS

VCCIO (V)

3.3

3.3

2.5

2.5

3.3

2.5

1.8

2

Altera Corporation

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