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A/D Converter. BT218 Datasheet |
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Preliminary Information
This document contains information on a new product. The parametric informa-
tion, although not fully characterized, is the result of testing initial devices
Bt218
20 MSPS Monolithic CMOS
8-bit Flash Video A/D Converter
The Bt218 is an 8-bit flash A/D converter designed specifically for video digitiz-
ing applications. A flash converter topology is used with 256 high-speed com-
parators in parallel to digitize the analog input signal.
Flexible input ranges enable NTSC and CCIR video signals to be digitized
without requiring a video amplifier.
The TTL-compatible output data and OVERFLOW are registered synchro-
nously with the clock signal. The OE* three-states the D[7:0] outputs asynchro-
nously to CLOCK.
The ZERO input is used to zero the comparators, while CLAMP allows DC
restoration of an AC-coupled video signal (by forcing the VIN input to the volt-
age on the LEVEL pin).
The Bt218 contains 256 high-speed comparators, a 255-to-8 encoder, an out-
put register, and a resistor divider network. Of the 256 comparators, 255 are
used to digitize the analog signal; the additional comparator is used to generate
the OVERFLOW bit.
Functional Block Diagram
ZERO
VIN
CLAMP
LEVEL
REF+
ZERO
CIRCUIT
1.2V
256
R/2
R 255
R
E
R 128
G
I
S
T
255 TO 8
127 ENCODER
E
R
VREF
CLOCK
D[7:0]
OE*
REF–
R
R
R/2
2
1
GND
VAA
Distinguishing Features
• 20 MSPS operation
• Bt208 pin compatibility
• No video amplifier requirement
• ±1/4 LSB typical DL error
• ±1/2 LSB typical IL error
• External zero and clamp control
• Overflow output
• On-Chip reference
• Output enable control
• TTL compatibility
• +5 V CMOS monolithic
construction
• 24-pin 0.3" DIP or 28-pin PLCC
packages
• Typical power dissipation: 500 mW
Applications
• Image processing
• Image capture
• Desktop publishing
• Graphic art systems
Related Products
• Bt252
• Bt254
• Bt261
Brooktree® Brooktree Division • Rockwell Semiconductor Systems, Inc. • 9868 Scranton Road • San Diego, CA 92121-3707
619-452-7580 • 1-800-2-BT-APPS • FAX: 619-452-1249 • Internet: apps@brooktree.com • L218_C
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Ordering Information
Model Number
Bt218KP20
Bt218KPJ20
Bt218EVM
Package
Speed
Ambient Temperature Range
24-Pin 0.3” Plastic DIP
20 MHz
0˚ to +70˚C
28-Pin Plastic J-Lead
20 MHz
0˚ to +70˚C
Evaluation Board for the Bt218KP. Includes a Bt218KP30.
Copyright © 1997 Brooktree Corporation. All rights reserved.
Print date: December 1992
Brooktree reserves the right to make changes to its products or specifications to improve performance, reliability, or
manufacturability. Information furnished by Brooktree Corporation is believed to be accurate and reliable. However, no
responsibility is assumed by Brooktree Corporation for its use; nor for any infringement of patents or other rights of third parties
which may result from its use. No license is granted by its implication or otherwise under any patent or patent rights of Brooktree
Corporation.
Brooktree products are not designed or intended for use in life support appliances, devices, or systems where malfunction of a
Brooktree product can reasonably be expected to result in personal injury or death. Brooktree customers using or selling Brooktree
products for use in such applications do so at their own risk and agree to fully indemnify Brooktree for any damages resulting from
such improper use or sale.
Brooktree is a registered trademark of Brooktree Corporation. Product names or services listed in this publication are for
identification purposes only, and may be trademarks or registered trademarks of their respective companies. All other marks
mentioned herein are the property of their respective holders.
Specifications are subject to change without notice.
PRINTED IN THE UNITED STATES OF AMERICA
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TABLE
OF CONTENTS
List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
List of Tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
Circuit Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Pin Descriptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
General Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Comparator Zeroing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Input Signal Clamping. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
PC Board Layout Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
PC Board Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Ground Planes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Power Planes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Supply Decoupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Signal Interconnect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Application Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Using the Internal Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Using An External Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
AC-Coupled VS. DC-Coupled Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Zeroing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Input Ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Output Noise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
PC Board Sockets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
ESD and Latchup Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Parametric Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
DC Electrical Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
AC Electrical Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Package Drawings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Revision History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Brooktree®
L218_C
iii
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