Browse Prior Art Database

USING RING OSCILLATORS TO DETERMINE MEMORY PERFORMANCE

IP.com Disclosure Number: IPCOM000006188D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2001-Dec-12
Document File: 2 page(s) / 94K

Publishing Venue

Motorola

Related People

Robert P. Dixon: AUTHOR [+2]

Abstract

The measurement of memory access times for high performance memories, requires very high reso- lution test equipment and careful design of test fix- tures. Only special purpose memory testers have the required resolution for production measurement, or laboratory bench type instruments for engineering evaluation.

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MOTOROLA INC. Technical Developments Volume 13 July 1991

   USING RING OSCILLATORS TO' DETERMINE MEMORY PERFORMANCE by Robert P. Dixon and Walter C. Seelbac$

INTRODUCTION

  The measurement of memory access times for high performance memories, requires very high reso- lution test equipment and careful design of test fix- tures. Only special purpose memory testers have the required resolution for production measurement, or laboratory bench type instruments for engineering evaluation.

The use of ring oscillators for gate delay measure-

ment is a simple well established technique. It gives accurate and repeatable determination of delays, using a minimum of 3 test points and a frequency counter, and is suitable for wafer probe and packaged devices. The critical path of a memory can also be configured as an oscillator, allowing memory delays to be deter- mined in a similar manner to simple gate delays. TECHNIQUES

  For a memory the read access time can be deter- mined by connecting the data output to the address input, and establishing stored data such that the path inverts. The stored data can be established by writing to the memory or by using ROM bits. The oscillator frequency can be divided down to ease testing.

The method is especially advantageous for evalua-

tion of new circuit designs, and process and technol- ogy changes. The inclusion of a memory ring on pro- duction Process Control patterns would allow memory performance to be monitored during wafer probe. It is suitable for both standard product memories as well as memories embedded in Application Specific IC (ASIC) products. The method is applicable to all memory types and in general to any logic function where an oscillator can be formed from the critical path of interest.

APPLICATIONS I

  This technique has bken applied to a 1 K word, 40 data bit BiCMOS SRAY ,using the MOSAIC 4 pro- cess. The mem...