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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

Impedance Matching

The impedance of the output driver is matched with the transmission line

impedance. Stratix and Stratix GX output buffers can match output

impedance to either 25 or 50 Ω. This impedance matching results in

properly terminated signals, improving signal integrity. This feature is

supported by all Stratix device I/O pins.

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When using impedance matching for an output buffer, variable

drive current strength and slow-slew rate features are not

available.

Figure 2 shows the on-chip impedance matching resistor for an output

driver.

Figure 2. Driver Impedance Matching

Impedance Matched

Driver (LVTTL, LVCMOS)

Rs

VCCIO = 1.8, 2.5, or 3.3 V

Z0

Receiving Buffer

(LVTTL, LVCMOS)

Parallel

Termination

(RT)

Terminator technology supports on-chip parallel termination for several

voltage-referenced I/O standards. To maintain signal integrity and save

board space, use Terminator technology resistors instead of external pull-

up termination resistors. Parallel termination is supported for SSTL-2,

SSTL-3, HSTL (class I and II), GTL, GTL+, and CTT I/O standards. All the

I/O pins in the top and bottom I/O banks support parallel termination.

Figure 3 shows the parallel termination connections for a Stratix device.

Altera Corporation

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