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Method for a quadrant strobe delay generator

IP.com Disclosure Number: IPCOM000009104D
Publication Date: 2002-Aug-07
Document File: 3 page(s) / 97K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a quadrant strobe delay generator. Benefits include improved performance, improved reliability, and an improved test environment.

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Method for a quadrant strobe delay generator

Disclosed is a method for a quadrant strobe delay generator. Benefits include improved performance, improved reliability, and an improved test environment.

Background

              In conventional ACIO loopback testing, receiver strobes must be delayed by a pre-determined amount in both directions (lag and/or lead) of the data. Special RC delay cell structures are used for the purpose. Typically, 32 delay cells with 6-bit routing are implemented (5 address bits, 1 control bit). These structures take considerable die area in the buffers on every interface but do not meet accuracy requirements because they are not validation-test compensated or calibrated. Making compensated and accurate delay cells is a mammoth task in terms of the return on investment.

Description

              The disclosed method uses quadrant strobe delay (QSD) for timing stress in loopback test (see Figure 1). It is a highly accurate, efficient, and scalable method being employed on multiple chipset products for stressing the timings in I/O loopback timing tests. The disclosed method fundamentally eliminates one of the root causes of flakiness of the conventional ACIO loopback testing, delay cell inaccuracy.

              The disclosed method removes delay cells and their associated routing. The method leverages the multiple clock phases available from a typical phased-lock loop (PLL). It is the most accurate timing source available on any chip. The derivatives used in QSD approach are equally accurate. The problem of the delay cell inaccuracy is prevented, freeing the die area, and eliminating the effort that goes into fabricating the delay cells. QSD also enables mo...