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Method for line driver amplitude tuning for process variation compensation

IP.com Disclosure Number: IPCOM000125124D
Publication Date: 2005-May-19
Document File: 4 page(s) / 151K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for line driver amplitude tuning for process variation compensation. Benefits include improved functionality, improved performance, and an improved design environment.

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Method for line driver amplitude tuning for process variation compensation

Disclosed is a method for line driver amplitude tuning for process variation compensation. Benefits include improved functionality, improved performance, and an improved design environment.

Background

 

              Conventionally, network controllers are trimmed during manufacturing to compensate for deviation due to process variation. Integrated circuits (ICs) that are trimmed are homogeneous. However, IC homogeneity is not sufficient in order to achieve a specified amplitude measured on the medium dependent interface (MDI) jack; in addition, board design must follow strict design rules and other components must be homogenous and accurate. These requirements increase the board cost, and are not always met in practice.

              If design rules are not met and amplitudes deviate from the specification, the on-chip nonvolatile memory (NVM) can be bypassed and different trimming values can be used. However, by doing so, the homogeneity of the IC is lost and each board must be tested and tuned separately, which increases the board cost.

              An alternative is to design the drivers to be extremely accurate so that each driver does not require trimming. Amplitude adjustment by programming the chip using on-board NVM can be used safely in this case. This alternative creates higher demand on the analog design, which may increase the design cost, the die size, and the total chip cost. Additionally, new fabrication processes may have more variation and new standards may require more complicated drivers, both of which make analog design accuracy more difficult.

              A way to achieve a two-phase process is to design two-stage analog tuning circuitry, such as two analog amplifiers with controlled gains in cascade. This type of design adds complication and cost.

              A two-phase process enables more flexibility in board design because IC homogeneity can be easily achieved, and yet amplitude can be tuned if necessary, without losing IC homogeneity.

General description

              The disclosed method enables of line driver amplitude tuning for process variation compensation.

              The key elements of the disclosed method include:

•             Two-phase correction procedure

•             Each driver's transmit amplitude trimmed to the design target during manufacturing to correct deviation due to process variation

•             Digital register loaded with trimming values to control the analog circuit

•             Repeated trimming if the measured amplitude does not meet the specification

•             Phase-2 tuning value logically added to the phase-1 value, so the per-board tuning does not interfere with the per-chip trimming

Advantages

              The disclosed method provides advantages, including:
•             Improved functionality due to providing driver amplitude tuning on a per-MDI basis
•             Improved functionality due to enabling retuning to comp...