HDM® Stacker Signal Integrity

Backward Crosstalk: Single Line | Multiline | Differential Pair

Reflection Amplitudes | Propagation Delay

In fast rise-time applications, electrical performance of a connector is critical. Minimizing crosstalk while maintaining high signal pin density is one of the HDM® Connector's strengths. The following tables summarize the effects of crosstalk using standard HDM® and shielded HDM PLUS® connectors. Users can mix both styles on the same daughterboard, and migrating from unshielded to shielded versions involves no rework of the backplane.

Single Line Backward Crosstalk

50-ohm system impedance. Connector rows A-F. Multiply crosstalk values by 0.75 to convert to 20% to 80% specified rise time. Backward crosstalk will typically be lower at system impedances above 50 ohms.

Signal-to- Ground Ratio	Available Signal Density	Rise Time 10-90%	HDM Connector	HDM+ Connector
1:1	15/cm (38/inch)	1ns	0.6 to 1.1%	0.3 to 0.7%
2:1	20/cm (51/inch)	1ns	1.6 to 4.2%	0.8 to 2.5%
5:1	25/cm (63/inch)	2ns	1.6 to 2.8%	0.8 to 1.8%

Multiline Backward Crosstalk

50-ohm system impedance. All adjacent lines driven. Connector rows A-F. Multiply crosstalk values by 0.75 to convert to 20% to 80% specified rise time. Backward crosstalk will typically be lower at system impedances above 50 ohms.

Signal-to- Ground Ratio	Available Signal Density	Rise Time 10-90%	HDM Connector	HDM+ Connector
1:1	15/cm (38/inch)	1ns	1.8 to 3.9%	1.3 to 2.3%
2:1	20/cm (51/inch)	1ns	8.7 to 12.6%	4.8 to 6.7%
5:1	25/cm (63/inch)	2ns	6.7 to 11.0%	3.7 to 5.0%

Differential Pair Backward Crosstalk

System ODD mode differential impedance = 100 ohms. All adjacent differential pairs driven, connector rows A-F.

Signal-to- Ground Ratio	Available Signal Density	Rise Time 10-90%	HDM Connector (Unshielded)
2:1	10 pairs/cm (25 pairs/inch)	0.3ns	3.0 to 5.5%

Reflection Amplitudes

50-ohm system impedance, connector rows A-F. Values in parentheses are fixed impedances corresponding to connector reflection levels. Multiply reflections by 0.75 to convert to 20% to 80% specified rise times.

Rise Time 10-90%	HDM Connector (Unshielded)	HDM+ Connector (Shielded)
1ns	-2.0 to 5.4% (48 to 56-ohm)	-3.0 to 3.0% (47 to 53-ohm)
2ns	-1.0 to 2.7% (49 to 53 ohm)	-1.5 to 1.5% (48.5 to 51.5-ohm)

Propagation Delay

(including typical real system contributions) 50-ohm system impedance, connector rows A-F.

	HDM Connector (Unshielded)	HDM+ Connector (Shielded)
Measured value, including the effects of 1pf pads and vias	130 to 235 ps	130 to 230 ps
Measured value, including the effects of 1pf pads and vias, plus the delays of stripline traces on the daughtercard	180 to 235 ps	180 to 230 ps