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LIMITING BUFFER AMPLIFIER FOR INTERFACING PROBE TO PROTOCOL ANALYZER

IP.com Disclosure Number: IPCOM000250616D
Publication Date: 2017-Aug-09
Document File: 4 page(s) / 523K

Publishing Venue

The IP.com Prior Art Database

Abstract

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LIMITING BUFFER AMPLIFIER FOR INTERFACING PROBE TO PROTOCOL ANALYZER

Michael T. McTigue

Background

The MIPI® M-PHY is a serial communication protocol for use in mobile systems. In terms of data rates or Gear, the M-PHY physical layer supports high-speed (HS) mode as well as low-speed such as pulse width modulated (PWM) and system-clock synchronous (SYS) modes. Specifically, for HS mode, the standard data rates are Gear1 (1.5Gb/s), Gear2 (2.9Gb/s), Gear3 (5.8Gb/s) and the new Gear4 (11.6Gb/s).

During M-PHY conformance test, a probe is used to acquire M-PHY bus signals for a protocol analyzer to capture and decode as per M-PHY standards over the communication channel. Conventional probing connectivity options between the M-PHY physical bus and protocol analyzer include an SMA connector probe, a multi-lead probe, an M.2 form factor interposer and a customized mid-bus probe built-on an existing footprint for PCI Express. The SMA connector, M.2 form factor interposer and multi-lead probes include a 50Ω input termination, while the Mid-bus probe is differentially terminated with 100Ω across the signal lines. The SMA connector, M.2 form factor interposer and multi-lead probes are used for Endpoint testing of various protocols related to M-PHY. The mid-bus probe is used for Mid-Bustesting on the M-PHY bus to emulate the transmit (TX) and receive (RX) modes.

Prior customized mid-bus probing setups include a flexible probe header cable with a probe header that matches the connector pad, a retention module that provides secure physical connection to the pad and a mid-bus pod, which contains electronics circuits to capture and amplify the signals before passing them to the protocol analyzer. This setup reliably supports up to HS Gear3 with 5.8Gb/s data rate transmission, but has not been tested for higher speed of M-PHY HS Gear4 mode. In fact, signal distortions can be created by lower performance probe circuitry when used for higher data rate testing such as mid-bus probing on the MIPI® M-PHY’s HS Gear4 mode. Therefore, it is critical to ensure that the selected high-bandwidth active probe does not contribute significant attenuation and loading to the 11.6Gb/s differential signals.

Description

The present disclosure provides a mid-bus probing system that leverages a high-bandwidth low-loading active oscilloscope probe with a limiting amplifier (with hibernate mode) as a probing means for protocol analysis. This solution is implementable across any digital communication protocol that uses the M-PHY physical layer.

An example of the mid-bus testing system is shown in Figure 1, consisting the limiting buffer amplifier module 2, as an interface between protocol analyzer 1 and high-bandwidth active probe 3 with differential-inputs and single-ended output. The high-bandwidth active probe 3 is used in mid-bus probing on the M-PHY bus signal lines through solder-in tips 3a, to monitor the transmission signals 4a from the first device under test, DUT1 t...