Electronic Circuits, Systems and Standards. The Best of EDN

222 Pages·1991·12.865 MB·English

by  Ian Hickman (Eds.)

Electronic Circuits, Systems and
Standards:
the Best of EDN
Edited by Ian Hickman
NEWNES
Newnes
An imprint of Butterworth-Heinemann Ltd
Halley Court, Jordan Hill, Oxford OX2 8EJ
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First published 1991
© EDN 1991
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1988 or under the terms of a licence issued by the Copyright
Licensing Agency Ltd, 33-34 Alfred Place, London, England WCIE
7DP. Applications for the copyright holder's written permission to
reproduce any part of this publication should be addressed to the
publishers.
British Library Cataloguing in Publication Data
Electronic circuits, systems and standards
1. Electronic equipment, circuits. Design
I. Hickman, Ian II. EDN
621.38153
ISBN 0 7506 0068 3
Printed and bound in Great Britain by
Butler and Tanner, Frome and London
Introduction
EDN first appeared with the issue dated May 8 always taken a keen interest in what goes on on
1956. It early proved itself a very useful source the other side of the stream from my own
of information and I have been saving articles particular specialization. Indeed, I was once in
from it since shortly after its debut. Of course, the dim and distant past a designer of state-of-
some of the earlier articles I saved have since the-art 10 MHz digital circuitry, when a 2N705
been overtaken by events. Thus, for example, a was the latest and best transistor going. Since
phase/frequency detector, as described on then, my interests have expanded with the
pages 55 to 59 of the issue of September 201976 technology so that I like to keep abreast of what
and realized in MSI, has long since been in- can be done in the field of computers, micro-
corporated as a matter of course in any self- controllers and other digital hardware, soft-
respecting synthesizer chip. ware and algorithms. Consequently, I will save
Since those early days, EDN has established an article if I can see that it is important, even if
for itself an unassailable position as the most it is not in my immediate area of specialization
useful and widely read of the controlled cir- - someone sometime at work is sure to ask me
culation electronics magazines. I get regular what I know about the topic. It may not be
copies of most of this type of magazine and much but I can usually point them in the right
frequently save articles from them for future direction. They can often take it on from there,
reference. These are kept in files, thinner or thanks to the helpful and commendable prac-
more bulging according to how useful I find tice of writers for EDN of including at the end of
that particular magazine. A measure of the an article, a list of references to other important
relative usefulness of EDN can be seen from the papers on the subject.
fact that it long ago overflowed its file and now Considerable thought was given as to what
threatens to overflow a second one. These files sort of order the following collection of articles
contain a wealth of useful information and should be arranged in. After all, some of them
circuit ideas, as I realize each time when I run to ten or more pages and others barely to
occasionally browse through them. Just a few one, whilst the range of topics covered is very
of them are reproduced in my book Analog diverse. In the end, they were carefully
Electronics, and it was whilst writing it that I
arranged in no sort of order at all, so that the
realized how useful and interesting a carefully
browser will find something different on
selected collection of articles from EDN would
almost every page. I hope you will find the
be to the practising electronics engineer. The
arrangement satisfactory; it is not nearly as
idea was suggested and in due course ap-
chaotic in practice as it sounds. For in addition
proved, and this book is the outcome.
to a table of contents with the entries arranged
My main qualifications for offering this se- in the order in which the articles appear, there
lection are simply that I have been collecting is a tabled Subject index. So if, for example, you
EDN articles for so long and also, I guess, that are interested in looking up digital circuits, just
no one else thought of doing it before me. My refer to the section circuits, digital, and you will
selection of articles for inclusion reflects my find all the circuits of this type listed in page
interests as a long-standing analog circuit de- order, and similarly for other topics. To assist
sign engineer and I make no apology for any in finding the item you are after, where it could
resultant slant to the mix of articles presented; be taken to fall into two categories, it is listed in
whoever had done the job, his or her profes- both sections; for instance, you will find a natty
sional background would have been certain to little AC coupled comparator circuit with an
influence the choice. However, this is not to say effectively infinite input time-constant listed
that digital topics are ignored, far from it. For under both analog and digital circuits. Inciden-
like any rounded, professional engineer, I have tally, this circuit is one of the many readers'
ix
ideas submitted to EDN's long standing Design number of these design ideas are included in
Ideas section. I know this to be very popular this volume, in addition to many informative
with readers; indeed many of my colleagues longer articles, either submitted or staff-
tell me that when their copy of EDN arrives, written. I have tried to include something to
they always turn to that section first. A large interest everyone, so now - please read on.
Ian Hickman
x
1 NOR gate controls oscillator
frequency
Simple FSK generator
There is an elegance about a circuit which achieves its function with great simplicity.
This FSK generator certainly falls into that category. Both centre frequency and shift will
be subject to component tolerances, but the circuit fills the bill as is for undemanding
applications; alternatively, presets can be designed in to allow adjustment to a standard
shift such as 170 or 850 Hz.
Richard Rice
Eaton Corp. Milwaukee, Wl
You can make a simple, stable frequency-shift-
keying (FSK) generator by adding an exclusive-OR
gate to a standard CMOS oscillator. In this circuit
(figure),the data input controls gate ICm, establish-
ing positive or negative feedback around the oscilla-
tor formed by ICIA, ICIB and ICK> INPUT ° )]^°>
When the data input goes LOW, ICm enters its
noninverting mode, and R increases capacitor C's
2
charging rate. When the input returns HIGH, ICm
inverts, and R reduces C's charging current, thus
2
lowering the oscillator's frequency.
Ri and C set the oscillators frequency range, and
R determines the circuit's frequency shift. To
2
ensure frequency stability, make R3 much greater
than Ri and use a high-quality feedback capacitor.
Note that the three gates constituting the oscillator
itself need not be exclusive-OR types—you can use An exclusive-OR gate (IC,o) turns a simple CMOS oscillator into
an FSK generator. When the data input goes HIGH, /C10 inverts,
any CMOS inverter. and negative feedback through R2 lowers the circuit's output
frequency. A LOW input results in positive feedback and a higher
output frequency.
1
2 Circuit converts voltage ratio
to frequency
Find the ratio of two voltages
This circuit provides an output voltage proportional to the ratio of two steady input
voltages. The same thing could of course be done with two ADCs and software, but in a
system without those facilities, this circuit provides a purely hardware implementation.
Watch out for settling time when one of the input voltages changes, though.
BobircS Florin Daniel that ramps between the V level and ground. When
D
The Electronic Research Institute, transistor Qi is on, for example, ICIA integrates -V /2
N
Bucharest, Rumania until its output equals V . At that time, the ICIB
D
comparator switches low, causing ICVs bistable output
The circuit of Fig 1 accepts two positive-voltage inputs to go low, which turns off Qi. ICIA'S output then ramps
VN and VD and provides a TTL-compatible output pulse in the negative direction. When the output reaches 0V,
train whose repetition rate is proportional to the ratio the ICic comparator switches, Qi turns on, and the cycle
VN/VD. Full-scale output frequency is about 100 Hz, repeats. Transistor Q2 converts the ICID output to
and linearity error is below 0.5%. TTL-compatible output logic levels.
The output F0 equals KVN/VD, where K=l/(4R2Ci) Setting VD to 1.00V yields a linear V/F converter
and provided Ri=R3. Op amp ICiA alternately inte- (F0=KVN), and setting VN to 1.00V yields a reciprocal
grates VN/2 and -VN/2, producing a sawtooth output V/F converter (F0=K/VD).
NOTES:
1. Id = LM339
2. Qi, Qa = BC172
3. DLDJ = 1N4148
Fig 1—Thi» voltage-ratio/frequency converter produces a TTL-compatible output pulse train that equals KVN/VD, where VN and VD are the
inputs and K=l>RjC,. Linearity error is less than 0.5%.
2
3 MIL-STD-1553 bus finds use
in diverse military systems
Details of an avionics data bus
The MIL-STD-1553 bus has been around for a number of years now, and in the latest
generation of military aircraft is likely to be supplanted by a fibre optics bus. However,
the 1553 bus is still very widely used and this staff-written article forms a useful
introduction. If you are an exclusively analog engineer, you may never need to grapple
with it in detail, but it is nice to know basically what it is - knowledge is never wasted.
The rounded engineer always likes to know what is on the other side of the fence from his
or her own particular specialisation.
Jon Titus, Associate Editor
"Military uses of the 1553 bus").
According to William Hartnett, DIVAD project engi-
Rather than routing individual cables to interconnect neering director at Ford Aerospace, the DIVAD system
equipment, many military designers use the MIL-STD- uses the 1553 bus because it offers a well-established
1553 bus. The 1553 bus is based on a twisted-pair cable protocol and because of the availability of a well-
that supports a bus controller and as many as 31 remote structured interface. Hartnett also says that the
devices. The result is a standard and reliable communi- lM-bps data rate of the 1553 bus is adequate for the
cations system that operates at 1M bps and uses a DIVAD system's needs.
standard 20-bit serial-transmission protocol. Besides
The 1553 bus standard was formulated in 1973 by a
adding reliability to electronic military hardware, the committee of the Society of Automotive Engineers. The
1553 bus requires no changes when suppliers offer committee revised and reissued the standard in 1975 as
upgraded or advanced system packages. Also, without MIL-STD-1553 A, a triservice standard. It was revised
rewiring an aircraft, technicians can quickly reconfig- again in 1978 when it was also adopted by NATO. The
ure electronic "black boxes" for a new mission, perhaps latest revision eliminates ambiguities and leaves fewer
concentrating the avionics on electronic countermea- interpretations to the designer. Both the original tri-
sures rather than on a specific weapon system. service standard and the revision (now called 1553B)
High-speed digital networks and fiber-optic systems specify that bus devices communicate information in
may eventually supplant the 12-year-old 1553 bus, but the biphase Manchester II format at a rate of 1M bps.
developing the relevant standards for military use The standard also specifies the rise and fall times for
takes time. However, the Department of Defense is the bus signals. Some manufacturers state that their
soliciting bids to install a 1773 fiber-optic bus system in devices are 1553 compatible, while others indicate the
the fourth upgrade of the US Navy's P-3C Orion, an specific standard that they comply with—1553A,
aircraft that detects, classifies, and tracks aircraft, 1553B, or both (see box, "MIL-STD-1553 specifica-
ships, and submarines. Nonetheless, most avionic and tions").
military system manufacturers believe that the 1553 The main bus consists of a shielded, twisted-pair
bus will be in use for some time. Similarly, most cable with a nominal impedance of 70ft. Transformers
military users indicate that a high-speed data bus may that provide the proper impedance ratios couple 1-MHz
be useful in the future, but the lM-bps data rate of the biphase signals from electronic systems to the bus. The
1553 bus is adequate for most current needs. Because 1553 standard lets you use short stubs (a foot or less)
the MIL-STD-1553 is well entrenched, a switch to a and long stubs (between 1 and 20 feet) to connect
new bus requires a major commitment by all three equipment to the main bus (Fig 1). Several manufac-
military services and their suppliers.
turers provide both bus terminators and transformer
Today, the 1553 bus is found primarily in navigation, couplers for 1553-based systems.
flight-control, defensive-system, communication, con- One supplier of transformers for the 1553 bus is ILC
trol, display, and offensive-system avionics hardware. Data Device. This manufacturer's transformers offer a
Although many believe that the 1553 bus is an Air Force range of turns ratios so that three models meet the
standard, the Navy and Army use several 1553-bus impedance-matching requirements of both short and
implementations in such ground-based applications as long stubs. For example, the BUS-25679 transformer
the Sgt York Division Air-Defense (DIVAD) gun sys- provides turns ratios of 1.4:1 or 2:1, depending on the
tem and seaborne applications such as the navigation windings you select. All three transformers measure
system for the Trident II submarine program (see box, 0.63 in. in length and width and have a height of 0.275
3
MIL-STD-1553 specifications
Although it's more than 12 years The MIL-STD-1553 document has a l-|xsec period because
old, MIL-STD-1553 (more prop- specifies the use of twisted-pair there are times when the bus is
erly called the Aircraft Internal wire for asynchronous-serial inactive. Besides transmission
Time Division Command/Re- communications between a bus formats, the MIL-STD-1553 doc-
sponse Multiplex Data Bus) re- controller and remote terminals. ument specifies voltage levels,
tains its popularity with both Transmissions occur at a fixed bus impedances, waveform rise
the military and the suppliers of rate of 1M bps, although it's and fall times, and device-coup-
military electronic equipment. more exact to say that each bit ling requirements.
Each device on the bus uses a
20-bit word to communicate com-
mand, data, and status informa-
BIT TIMES 1 1 2 3 4 5 67 9 110 I 11 112 113 114 115 I 16 117 118 119 120 tion (Fig A). Each word starts
with a 3-bit synchronization se-
quence that lets the receiver
COMMAND I | 5 1 5 5 1
WORD ' 1 identify the transmission type,
1 SYNC TAEDRDMRIENSASL £ SUBMAODDDER ESS/ DACTAO UWNOTR D Pi aonddd -ap awriotyrd bailtw. Rayesm eonvdins gw tihthe an
three synchronization bits and
DATA WORD the parity bit from the transmis-
sion leaves you 16 bits for infor-
I SYNC mation.
The command word uses five
STATUS WORD bits to identify the remote ter-
minal that will receive the trans-
TERMINAL
ADDRESS 2 mission and another five bits to
OUJC ut.i l <-> f- *- w identify a subdevice (if any) con-
£ => 3 _J trolled by the remote terminal
I .< 1 8 CZ CI O CI O d5 that is to receive the transmis-
O CD < ^
J- CO CO OC sion. A set of five word-count
o => 2 uj
and mode-code bits tells the re-
mote terminal how many data
words will follow. These five bits
also specify a mode code that
causes bus devices to perform
specific control operations. Al-
Fie; A—The format for the command, data, and status words shows that each word
contains 20 bits. The first three bits provide synchronization information, and the last though there are 32 possible
bit contains parity data. mode codes, only 15 are allowed
or 0.300 in., depending on the version you choose. input signals and pass on to the receiver only those
A supplier of prepackaged bus-coupling devices is signals that exceed a preset threshold. Digital bus-
SCI Systems Inc, which produces 24 such devices. You controller circuits use TTL-compatible signals to com-
can specify combinations of connectors, terminating municate with the bus receiver and transmitter
resistors, and outputs for one or two stubs. These modules.
couplers offer you a variety of bus connectors, but the Although these devices are called transmitters, re-
choice may depend on the connectors used in your bus. ceivers, and transceivers, they don't encode or decode
Available connectors include the BJ30, BJ77, BJ377, digital information. The transmitters accept biphase
and BJ150 made by Trompeter Electronics Inc TTL signals and drive the transformer that couples the
(Chatsworth, CA) and the D-602-55 socket from Ray- overall system to the 1553 bus. Receivers perform the
chem Corp (Menlo Park, CA). reverse operation, converting bus signals into biphase
To design the circuits that transfer information to and TTL signals for the bus-control circuits. For example,
from the bus, you'll have to consider the noise-rejec- Aeroflex Laboratories' ARX-18553 transceiver module
tion, signal-threshold, and rise-time requirements of comes in an 18-pin DIP and contains both a receiver and
your system. Commercially available transmitter and a transmitter circuit. The transmitter accepts biphase
receiver modules control the proper voltage levels and TTL signals and produces a 27V p-p differential signal
rise times for transmissions. These modules also filter across a 140ft load. Internally set control voltages let
4
CONTROLLER-TO- RECEIVE DATA DATA DATA LAST NEXT
TTRERAMNSINFAELR COMMAND WO1R D WO2R D WO3R D WDOATRAD COWMOMRADN D
STATUS
TERMINAL-TO- WORD
CONTROLLER
TRANSFER
RESPONSE I INTERMESSAGE
TIME GAP
Fig B—A transmission sequence contains a command word followed by data. After receiving the data error free, the receiver
responds by sending a status word to the transmitter.
by the 1553 standard. The com- transmission again or can query format. Receivers don't acknowl-
mand word includes a transmit/ the receiver for its status infor- edge broadcasts because simulta-
receive bit that tells the remote mation to find out what type of neous responses from all the re-
terminal to operate in either the error occurred. mote terminals would cause the
receive or transmit mode. Although the status word bus to crash. The bus controller
Besides the synchronization seems complex, the 1553 stand- can request responses from indi-
and parity bits, the data word ard requires only the data-parity vidual remote terminals when
has no format. You can thus use (or message-error) bit, located you need specific status
the 16 data bits as you wish, but at bit position nine. Except for information.
you must use 16 of them. the synchronization, parity, arid The bus-interface circuits en-
The status word transfers flag remote-terminal address bits, code bus signals in Manchester
and status information between the other status bits are option- II biphase format, which pro-
devices on the 1553 bus. When a al. Fig B shows a transmission duces a zero-voltage crossing in
bus device receives an error-free sequence. the middle of each bit position.
transmission, it sends a status The 1553 standard specifies 10 The only exceptions are the syn-
word to the transmitting device. types of information-transfer for- chronization bits, which have
If a device receives information mats. Six of these transfer data their own format. Because this
that contains an error, such as and status information between format isn't a legal Manchester
incorrect parity or an extra bit, the bus controller and a selected code, the bus devices don't mis-
no status word is sent. When remote terminal or between one take it for data. The Manches-
the transmitter doesn't get the remote terminal and another. ter-encoded information is self-
expected status response in a Four formats apply to broadcasts clocking and has no dc com-
given time, it knows that some- of information from the bus con- ponent, which makes it ideal
thing is wrong with the receiv- troller to all of the remote termi- for asynchronous transformer-
er. The transmitter can send the nals that support the broadcast coupled bus systems.
the receivers ignore signals that are below a 0.3V p-p the threshold from 0V to as much as 2V p-p. The
threshold. Only those signals that exceed a 1.0V p-p manufacturer also supplies the BUS-8559 transceiver,
level are converted to TTL levels and sent to the which has a continuously variable output that is set by a
bus-control circuits. control voltage between 0 and 15V at a control pin. You
Another Aeroflex module is the ARX-28553, avail- can vary the transmitter's output level between 0 and
able in a 36-pin DIP and a 36-pin flat package. This 6.5V p-p. By transmitting a series of bus signals at
device contains two separate transceivers for use in a different voltages, you can test the response of a bus
system that requires two separate but equivalent (dual- receiver.
redundant) buses. The manufacturer's modules operate
from either ± 12V or ± 15V power supplies and require
an impedance-matching transformer for connection to a
1553 bus.
ILC Data Device Corp offers several types of bus
transceivers, including the BUS-8554 transceiver,
which rejects 1553 bus signals that are below a 750-mV
p-p threshold. By connecting a threshold-programming
pin to ground through an external resistor you can vary
5
The COM-1553A transceiver chip provides 15 lines
for control and status signals. Eight bidirectional data
lines transfer data to and from the chip and its host
TRANSFORMER COUPLED computer. Instead of using a complete 16-bit word, the
r ■» COM-1553A chip transfers data one byte at a time.
DIRECT COUPLED
Thus, at the lM-bps data rate, the chip can receive
sequential data bytes that are within 600 nsec of each
other. If the transceiver chip's host is a computer
system, you may need to use a first-in, first-out (FIFO)
buffer or other high-speed memory system between the
bus-controller chip and your computer.
Although the 1553 bus provides a standard
format, designers have leeway in deciding
how to use the bus data.
The COM-1553A chip performs parallel-to-serial and
serial-to-parallel conversions, and you have a choice of
operating it either as a remote terminal or as a 1553 bus
controller. Each bus has only one controller that man-
ages and oversees all of the bus operations. A system
that can switch a device from remote-terminal to bus-
controller operation can include computer-based re-
mote terminals that can take over the bus controller's
Fig 1—Two types of transformer coupling let you configure a bus
device with either a long or a short stub. Long stubs require two functions if the main bus controller fails.
transformers, one at the main bus cable and a second at the bus
To properly format the information it transfers to and
device.
from the 1553 bus, the COM-1553A chip requires an
Control chips external Manchester encoder/decoder chip. Standard
Microsystems recommends the HD-15531 CMOS Man-
Although transceiver modules provide access to the
chester encoder/decoder from Harris Semiconductor.
bus, you'll need additional circuits to connect the trans-
The COM-1553A and the HD-15531 together require a
ceiver to your overall avionic system. These control
5V power supply. The COM-1553A is also available on a
circuits generate the encoded information for the 1553
pc board from Grumman Aerospace Corp, which joined
bus, and they receive and decode bus information for
the system (Fig 2). The COM-1553A and COM-1553B with Standard Microsystems to develop the 1553A chip.
Standard Microsystems also produces the COM-
chips from Standard Microsystems Corp meet the bus
standards and contain the circuits that support the 1553 1553B chip, an upgraded bus transceiver that is not a
bus protocol. pin-for-pin replacement for the COM-1553A device. The
BUS-INTERFACE CIRCUITS
I -
1
i ,
TTMOROA DBNUUSLSFE O RMER TRANBSUCSE IVER , !1i MAEDNNECCCHOOEDDSEETRRE R CORAMESDPGHADAINIRSFRDETTA SELT SRO R COLNOTGRICO L
•
| { i 1 i
(MAY REQUIRE r
1 EXTERNAL CHIPS 1 HANDSHAKE. STATUS. AND 1
1 IN SOME SYSTEMS.) | t BUS BUFFERS to |
i \\ is
y
ST S
ATUS HANDSHAKE DATA BU
V
TO BUS CONTROLLER OR
REMOTE TERMINAL
Fig 2—Bus controllers include circuits that decode a transmission and recognize a 5-bit terminal address. The transmitter section
serializes the data and adds the synchronization bits and an odd-parity bit. Some devices include a Manchester encoder-decoder circuit.
6