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Digital Electronics
Principles & Applications
Seventh Edition
Roger L. Tokheim
Chapter 5
IC Specifications
and Simple Interfacing
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
INTRODUCTION
• Logic Levels/Noise Margin
• Interfacing Families of ICs
• Other Specifications
• MOS and CMOS ICs
• Interfacing with Switches
• Interfacing with LEDs
• Interfacing with Buzzers,
Relays, Motors and Solenoids
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
INTRODUCTION (Continued)
• Interfacing Using an Optoisolator
• Current Sourcing and Sinking
• Using a Stepper Motor
• Using a Servo Motor
• Hall-effect Sensor/Switch
• Using the Hall-effect Switch
• BASIC Stamp® Driving a Servo
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Logic Levels / Noise Margin
• Voltage characteristic - defines logical
0 (LOW) or logical 1 (HIGH)
• Noise immunity (noise margin)- logic
circuit’s insensitivity or resistance to
undesired voltages called “noise.”
TTL Voltage Profiles Chart
Input
Output
LOW GND - 0.8V
HIGH
2.0 - 5.5V
GND - 0.4V (0.1V typical)
2.4 - 5.5V (3.5V typical)
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
1. An input voltage of 0.4V to a TTL IC (5V
power supply) would be interpreted as a
logical __________ (0 or LOW, 1 or HIGH).
0 or LOW
2. An input voltage of 3V to a TTL IC (5V
power supply) would be interpreted as a
logical __________ (0 or LOW, 1 or HIGH).
1 or HIGH
3. A typical HIGH output from a TTL IC (5V
power supply) would be about __________
(0.1V, 3.5V).
3.5V
4. A logic circuit’s insensitivity or resistance
to undesired voltages (called noise) is
__________ (noise margin, noise clutter).
noise margin
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Input Voltage Profiles –
TTL and 4000 Series CMOS
Input Voltage Profiles
+5V
TTL 100% CMOS
HIGH
LOW
GND
90%
80% HIGH
70%
60%
50%
40%
30%
20%
10% LOW
0%
+10V
CAUTION
Undefined
OutputUndefined
VLOW
profile differs
logic
HIGH
reading
may
0+3
toprobe
+3V
for
CMOS
Other
families
profile
to +7VVfor
CMOSdiffers
depending
on
+7V
+10V
- for
CMOS
0vary
tototo
+0.8V
TTL
+0.8V
+2.0Vin
TTL
manufacturer
+2V to +5V - TTL
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
1. An inexpensive hand-held instrument called a
__________ (logic probe, oscilloscope) is commonly
used to check logic levels in TTL or CMOS circuits.
logic probe
2. An input voltage of 1V to a CMOS IC (10V power
supply) would be interpreted as a(n) __________
(HIGH, LOW, undefined) input.
LOW
3. An input voltage of 5V to a CMOS IC (10V power
supply) would be interpreted as a(n) __________
(HIGH, LOW, undefined) input.
undefined
4. An input voltage of 9V to a CMOS IC (10V power
supply) would be interpreted as a(n) __________
(HIGH, LOW, undefined) input.
HIGH
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
TTL Voltage Profiles
INPUT
OUTPUT
+5V
+5V
H
H
Input
+1.2V
Input==+0.3V
+4V
+2.2V
Output = ?
+2.4V
+2V
?
?
Undefined
?
HIGH
LOW
+0.8V
Low
GND
+0.4V
GND
Low
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
TTL-to-CMOS Interfacing
• Interfacing is the design of circuitry between devices.
• Interface circuitry shifts levels of voltage & current for compatibility.
• TTL and CMOS HIGH and LOW voltage profiles are different.
• Current requirements for TTL and CMOS are different.
• Example:
Pull up resistor
Design Notes:
1. Output current of TTL OK to
drive CMOS device.
2. Output voltage profile does NOT
fit CMOS input voltage profile.
3. Use pull up resistor as interface
device to adjust voltage profiles.
Standard TTL
CMOS
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
1. The design of circuitry that translates
voltages and currents between devices (such
as between TTL and CMOS) is called
__________ (boundary scanning, interfacing).
2. Interface circuitry shifts levels of
__________ (current and voltage, time and
temperature) for compatibility between
two devices or circuits.
3. In TTL-to-CMOS interfacing, a __________
(pull-up, temperature-sensitive) resistor is
used to shift voltage levels.
4. The voltage profiles for TTL and CMOS
are __________ (different, the same).
interfacing
current and
voltage
pull-up
different
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
CMOS-to-TTL Interfacing
• Interfacing is the design of circuitry between devices.
• Interface circuitry shifts levels of current & voltage for
compatibility.
• CMOS and TTL voltage profiles are different.
• Current requirements for CMOS and TTL are different.
• Example:
CMOS buffer
(like 4050 IC)
CMOS
Design Notes:
1. Output voltage profile of CMOS
is OK to drive TTL inputs.
2. Output current from CMOS is
NOT enough to drive standard
TTL.
3. Use special purpose CMOS buffer
IC to adjust the current levels.
Standard TTL
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
1. The design of circuitry to make TTL-toCMOS or CMOS-to-TTL connections is
called __________.
interfacing
2. TTL and CMOS voltage profiles are
__________ (different, the same).
different
3. TTL and CMOS current input
requirements and output drive capabilities
are __________ (different, the same).
different
4. Interfacing standard TTL-to-CMOS
involves using a(n) __________ (buffer,
pull-up resistor) between the input TTL
and CMOS devices.
pull-up resistor
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Other Digital IC Specifications
• Drive Capabilities - sometimes referred to as fan-in
or fan-out.
• Fan Out - number of inputs of a logic family that can
be driven by a single output. The drive capability of
outputs.
• Fan In - the load an input places on an output.
• Propagation Delay - has to do with the “speed” of
the logic element. Lower propagation delays mean
higher speed which is a desirable characteristic.
• Power Dissipation - generally, as propagation delays
decrease, power consumption and heat generation
increase. CMOS is noted for low power
consumption.
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
1. The __________ (fan out, quantum
equivalence) refers to the drive
capability of the outputs of a digital IC.
2. Faster digital ICs (a desirable
characteristic) have __________
(higher, lower) propagation delays.
fan out
lower
3. The __________ (CMOS, TTL) family
of digital ICs is known for its very low
power consumption and is commonly
used in battery powered products.
CMOS
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
1. The drive capability of logic device outputs is
sometimes called __________ (fan in, fan out).
It is the number of inputs of a logic family
that can be driven by a single output.
fan out
2. CMOS devices are noted for their extremely
__________ (high, low) power consumption.
low
3. A logic device with a low propagation delay
would be considered to be a __________
(high, low) speed device.
high
4. Several desirable characteristics of logic
devices are good drive capabilities, low
power consumption, and __________
(high, low) propagation delays.
low
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
MOS and CMOS ICs
• MOS stands for Metal-Oxide Semiconductor.
• PMOS, NMOS, and CMOS are three technologies used to
manufacture ICs. TTL is another very fast technology.
• NMOS stands for Negative-channel Metal-Oxide
Semiconductor. NMOS ICs are faster than PMOS.
• PMOS stands for Positive-channel Metal-Oxide Semiconductor.
• CMOS stands for Complementary Metal-Oxide Semiconductor.
Both PMOS and NMOS devices are used it its manufacture.
• CMOS ICs are noted for exceptionally low power consumption.
• CMOS ICs were slower than bipolar digital ICs (such as TTL
devices).
• Transmission gates or bilateral switches are unique digital
devices created using CMOS technology.
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
1. The MOS part of CMOS stands for metal-oxide
semiconductor which is a technology used in
producing ICs with __________ (high, low)
power requirements.
low
2. PMOS, NMOS and CMOS are three technologies
that use field-effect transistors to fabricate
modern digital ICs. (True or False)
True
3. CMOS stands for negative-channel metal-oxide
semiconductor and is a type of extremely highspeed high-power consumption digital IC.
(True or False)
False
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Interfacing with Switches
Switch-to-TTL interfaces
+5V
Pull up resistor
HIGH
LOW
HIGH
LOW
Pull
Pull down
down resistor
resistor
INPUT
INPUT
INPUT
pulled
HIGH
by
INPUT
pulled
HIGH
by
pulled
LOW
by
pull
up
resistor
pulled
LOW
by
pull switch
up resistor
switch
INPUT
INPUT
INPUT
pulled
LOW
pulled
LOW by
by
pulled
by
pulled HIGH
HIGH
by
pull down
down
resistor
pull
resistor
switch
switch
Switch-to-CMOS interfaces
With pull up resistor
With pull down resistor
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
1. The component labeled A in
the interfacing circuit is called
a __________ (pull-down, pullup) resistor and is holding the
input to the inverter HIGH.
2. The component labeled B in
the interfacing circuit is
called a __________ (pulldown, pull-up) resistor and is
holding the input to the
inverter LOW.
3. The output at point C is
currently __________ (HIGH,
LOW) because the pull-down
resistor is holding the
inverter’s input LOW.
A
pull-up
pull-down
B
C
HIGH
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Switch Debouncing
• Mechanical switches that serve as inputs for some
digital circuits (like counters) may need switch
debouncing.
• A Low-to-High switch transition can result
in H-L-H bounces.
• A demonstration of a debouncing circuit in action.
Notice
No switch bounce!
Debouncing
Latch
HIGH
LOW
time
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
1. The output waveform at A going L-H-L-H is
referred to as a(n) __________ (analog, digital)
signal.
digital
2. The block labeled B is a switch __________ latch.
debouncing
3. The L-H-L-H output of the SPDT switch on the left
is debounced by the electronic device labeled B.
(True or False)
True
A
B
HIGH
LOW
time
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Interfacing TTL or CMOS to LEDs
+5 V
Either TTL or CMOS ICs can
drive an LED using a transistor.
150 W
Left arrow key on keyboard to
erase and see action again.
HIGH
LOW
LOW
HIGH
TTL or
CMOS
Transistor
OffON
33 kW
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
1. If point A goes HIGH point B will go LOW
and the transistor will turn off causing the
LED to __________ (turn off, turn on).
turn off
2. If point B goes HIGH and the transistor
will turn on causing the LED to
__________ (turn off, turn on).
turn on
3. The inverter can be from either the TTL
or CMOS family of ICs and be able to
drive the indicator LED. (True or False)
A
+5V
True
LED
B
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Interfacing with Buzzers,
Relays, Motors & Solenoids
• Piezo buzzer - a signaling device drawing less
current than older buzzers and bells.
• DC or AC motors - produce continuous rotary
motion. (Motor voltages and current not
compatible with logic circuits.)
• Solenoid - a device that can produce linear motion.
• Relay - a device to isolate logic device from highvoltage/current circuit.
• Optoisolator - a device to isolate logic device from
high-voltage/current circuit.
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Interfacing with a Piezo Buzzer
Left arrow on keyboard to
erase and see action again.
No sound
Buzzer
sounds
Transistor ON
OFF
Transistor
LOW
HIGH
Goes
Goes
HIGH
LOW
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
1. When the input to the inverter
goes LOW, the buzzer
__________ (does not sound,
sounds).
2. When the input to the inverter
goes HIGH, the input to the
transistor goes LOW which turns
__________ (OFF, ON) both the
transistor and the buzzer.
sounds
OFF
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Isolation-Logic to High Voltage/Current
• Electromechanical Relays - older method
of isolation. Relays are expensive, heavy,
and produce “noise.”
• Optoisolator (Optocoupler) - light weight
alternative to electromagnetic relay when
interfacing with logic circuits.
• Solid State Relay - a heavy-duty version of
an optoisolator.
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Interfacing Using a Relay
N.O. relay contacts
Electromechanical Relay
Driver Transistor
Left arrow key on keyboard
to erase and view again.
DC Motor (12 Volt)
Low Voltage (+5V)
Side of circuit
High Voltage (12V)
Side of circuit
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Interfacing Using a Relay
to Control a DC Motor
Coil
notenergized
energized
Coil
N.O.
open
N.O.contacts
contactsremain
snap closed
DC motor
does runs
not run
DC motor
HIGH
LOW
LOW
HIGH
Transistor
Transistor
Off
ON
(Left arrow key on keyboard
to erase and view again)
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
1.
If the input to the inverter is LOW, the
transistor will turn ON and the relay coil
will be energized. (True or False)
2. If the input to the inverter is LOW, the
transistor will turn ON, the relay coil will
be energized, the N.O. relay contacts close,
and the motor will run. (True or False)
3. If the input to the
inverter is HIGH,
the DC motor
__________ (will,
will not) run.
True
True
will not
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Optical Isolation
Solid state relay
or optoisolator
120 VAC
5 VDC
Load ground
(Left click for L-to-H input signal)
Logic ground
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Interfacing Using on Optoisolator
Left arrow key on keyboard
to erase and view again)
Buzzer
sounds
No Sound
HIGH
LOW
(Left click for action)
LOW at
at pin
pin 22 of
of IC
IC
HIGH
LEDLED
does lights
not light
ICs
transistor
ON
Transistor
OFF
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
1. If the input to the inverter is HIGH, the LED inside
the optoisolator lights, the transistor turns
__________ (ON and the buzzer sounds, OFF and
the buzzer is silent).
ON and the
buzzer sounds
2. The optoisolator IC isolates the lower voltage (5V)
input from the higher voltage (12V) output. (True
or False)
True
3. There is a low
resistance electrical
connection between
the input logic
circuits and the
output buzzer circuit
because of the
optoisolator IC.
(True or False)
False
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
ICs Sourcing and Sinking Current
An example of the IC
Sourcing Current
To drive the output LED
(conventional current flow)
Active-HIGH output
Notice the IC has
Active-HIGH output
An example of the IC
Sinking Current
To drive the output LED
(conventional current flow)
Notice the IC has
Active-LOW output
Active-LOW output
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Stepper- and Servo-Motors
• Stepper motor - a motor that rotates a fixed angle
(in discrete steps) for each input pulse. The logic
levels applied to each field coil are defined in the
control sequence for the stepper motor. Can reverse
direction by progressing either up or down the
control sequence.
• Servo motor (hobby-type servo) - a motor widely
used in radio-control vehicles that rotates to an
angle defined by the pulse width of the input signal.
It is driven by pulse-width modulation. The pulse
widths for hobby servos motors range from about
1- to 2-msec. Hobby servos have a limited range of
rotation such as 180 degrees.
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Stepper Motor Operation
Sequence Chart
Step
1
2
3
4
1
2
L1
1
0
0
1
1
0
L1 L2 L2
0 1 0
1 1 0
1 0 1
0 0 1
0 1 0
1 1 0
Note:
Use --> key for CW,
then <-- key for CCW rotation)
L1
L1
L2
L2
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Servo Motor
Input=
Input=
Input=
1.5
msec
12msec
msec
positive
positive
pulse
positivepulse
pulse
50Hz
50Hz
50Hz
Output=centered
Output=CW
Output=CCW
+5V
Input
Left arrow on keyboard to
erase and see action again.
End of output shaft
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
1. The angular position of a servo motor’s shaft
can be modified by varying the pulse voltage
entering the input to the device. (True or False)
False
2. Stepping upward or downward through a
control sequence results in the stepping action
(in small discrete steps) of a stepper motor.
(True or False)
True
3. If sequencing downward through the control
sequence of a stepper motor causes CCW
rotation, then reversing and going upwards
CW or
though the control sequence will cause
__________ (CW, no) rotation of the output shaft. clockwise
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Hall-Effect Switch IC
Bipolar Hall-effect Switch IC
Output pin of IC
Schmitt trigger
(digitizes output)
GND pin
Vcc (+5V)
Hall-effect sensor
Output NPN transistor
(Left arrow on keyboard to
erase and view again)
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Using the Hall-Effect Switch IC
(Left arrow on
keyboard to erase
and view again)
TransistorOFF
ON
Transistor
Pin 33 goes
goes HIGH
LOW
Pin
SNpole
poleapproaching
approaching
Hall-effect
Hall-effectsensor
sensor
Turns
ON
transistor
Turns OFF transistor
LEDislights
LED
OFF
South
Northpole
pole
South pole
North pole
(Left click for action)
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
1. If the S pole of a magnet approaches the
Hall-effect sensor of this IC the transistor
will turn __________ (OFF and the LED will ON and the LED will light
not light, ON and the LED will light).
2. If the N pole of a magnet
approaches the Hall-effect
sensor of this IC the transistor
will turn OFF and the LED
will not light. (True or False)
3. The output of the Hall-effect
sensor is analog in nature but
the device called a(n)
__________ (NPN transistor,
Schmitt trigger) changes this
to a digital output.
True
Schmitt
trigger
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
BASIC Stamp® Module
Driving a Servo Motor
Step 3: Disconnect PC from BS2 module
PBASIC Code
FOR C= 1 to 25
PULSOUT 14, 1000
‘CCW rotation
PAUSE 20
NEXT
Step 2: Download program from
PC
moduleon PC in PBASIC
Step
1:
Write
program
FOR
C=to1BS2
toOFF
25
Step
4: Power
and ON (BS2 module).
Keymotor
lines14,
of500
code
are:
Observe
shaft
rotation
as program
runs.
PULSOUT
‘CW
rotation
Output- pin 14
FOR
C = 20
1 to 25
‘Begin counting loop
PAUSE
PULSOUT
14, 1000 ‘Emits 2ms pulses—CCW rotation
NEXT
PAUSE 20‘Pause 20ms
NEXT
‘Repeat if C<25
FOR C = 1 to 25
‘Begin counting loop
PULSOUT 14, 500 ‘Emits 1ms pulses—CW rotation
PAUSE 20‘Pause 20ms
NEXT
‘Repeat if C<25
Hobby Servo Motor
Left arrow on keyboard to erase and view again
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
1. The PULSOUT 14, 1000 line of code will cause the BASIC Stamp®
to output a _____ (HIGH, LOW) pulse for 2ms (1000 x 2usec= 2ms)
at pin 14 of the BS2 module.
2. The PAUSE 20 line of code will cause the BASIC Stamp® to
output a LOW for 20ms. (True or False)
3. The FOR-NEXT loop will be repeated
_____ (20, 1000) times.
HIGH
True
20
PBASIC code (BS2 module)
4. The 2ms positive output pulse generated
by BS2 module can be used to rotate a
hobby _____(servo, ac) motor in the CCW servo
direction.
FOR C= 1 to 20
PULSOUT 14, 1000
PAUSE 20
NEXT
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
REVIEW
• Logic Levels/Noise Margin
• Interfacing Families of ICs
• Other Specifications
• MOS and CMOS ICs
• Interfacing with Switches
• Interfacing with LEDs
• Interfacing with Buzzers,
Relays, Motors and Solenoids
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
REVIEW (Continued)
• Interfacing Using an Optoisolator
• Current Sourcing and Sinking
• Using a Stepper Motor
• Using a Servo Motor
• Hall-effect Sensor/Switch
• Using the Hall-effect Switch
• BASIC Stamp® Driving a Servo
©2008 The McGraw-Hill Companies, Inc. All rights reserved.