Browse Prior Art Database

COARSE FLASH ANALOG TO DIGITAL CONVERTER

IP.com Disclosure Number: IPCOM000007458D
Original Publication Date: 1995-Jul-01
Included in the Prior Art Database: 2002-Mar-28
Document File: 2 page(s) / 66K

Publishing Venue

Motorola

Related People

Virgilio A. Fernandez: AUTHOR

Abstract

Traditionally flash A/D converters are implemen- ted using comparators. The comparators are very accurate, but have the drawbacks of continuous cur- rent consumption, and the need for external volt- age(s) reference(s).

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 77% of the total text.

Page 1 of 2

MolylRoLA Technical Developments

COARSE FLASH ANALOG TO DIGITAL CONVERTER

by Virgilio A. Fernandez

  Traditionally flash A/D converters are implemen- ted using comparators. The comparators are very accurate, but have the drawbacks of continuous cur- rent consumption, and the need for external volt- age(s) reference(s).

  The Coarse Flash A/D Converter presented here has the following advantages: it uses no standby cur- rent due to its inherent digital scheme, it can be integrated in a digital process, it requires no voltage reference, and it is very fast. The main disadvantage is that it is not very accurate and hence the number of bits it can resolve is limited.

The coarse flash A/D converter is comprised of one inverter with hysteresis per bit of resolution i.e.

a 4 bit A/D would need 4 inverters. A requirement for the A/D functionality is that each inverter must have a different trip point or hysteresis (See Figure 1 INVO, INVI, INV2, or INV3) since each inverter represents l-bit ofthe A/D action. Furthermore, one latch per bit is required to hold the output value, and a separate "sample" control line determines when the user wants to sample the data. Figure 1 shows an example of a 4-bit coarse A/D converter without the output latches.

  For example, if inverter INVO trip point is OS\! INVl=l.O\! INV2=1.5\! INV3=2.0\! and the input VIN is SOOmV, when the "SAMPLE" line goes high B3, B2, and Bl will go high while BO will remain a low.

0 Motorola. Inc. 19% 81 July 1995...