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Method for a PCI Express TX buffer characterization pad

IP.com Disclosure Number: IPCOM000145867D
Publication Date: 2007-Jan-30
Document File: 3 page(s) / 205K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a PCI Express transmit (TX) buffer characterization pad. Benefits include improved functionality and improved performance.

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Method for a PCI Express TX buffer characterization pad

Disclosed is a PCI Express transmit (TX) buffer characterization pad. Benefits include improved functionality and improved performance.

Background

      PCI Express is a trademark of PCI-SIG, the special interest group responsible for the parameterized configuration interaction input/output environment.

      The PCI Express base specification includes a parameter for signal integrity measurement to be validated at the pins of the transmitting chip.

      Probing at the transmitter pins in the conventional implementation is not possible for the following reasons:

•     No specification exists for measuring a transmitter when connected to a receiver through a transmission line.

•     DC blocking capacitors (caps) are too far from the transmitter pins.

•     No provisions exist to place termination resistors near the transmitter (either separately or in place of the blocking caps).

•     No convenient ground locations exist for referencing to measurements.

      Existing printed circuit boards (PCBs) typically include blocking caps on the primary side of the board. Differential signal probing at the caps is not accurate due to the relative proximity to the transmitter pins. Additionally, the probe points are not disconnected from the transmission line that connects to the receiver chip. Single-ended measurements are typically not possible due to the l...