Code Lock Security details

7/23/2019 Code Lock Security details

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Circuit diagram of project:

Simulation of project in Proteus ISIS:



PCB Layout of microcontroller board:



3D view of microcontroller board:



PCB Layout of eypad matri! board:



3D view of eypad matri! board:



PCB Layout of L"#3D $motor driver% board:



3D view of L"#3D $motor driver% board:



Components



Diode:&

In electronics, a diode is a component that restricts the direction of movement of

charge carriers. Essentially, it allows an electric current to flow in one direction,

but blocks it in the opposite direction. Today the most common diodes are made

from semiconductor materials such as silicon or germanium.

Semiconductor Diodes

Most modern diodes are based on semiconductor P- !unctions. In a P- diode,

conventional current can flow from the P-type side "the anode# to the -type side

"the cathode#, but not in the opposite direction. $ semiconductor diode s current-

voltage, or I-%, characteristic curve is ascribed to the behaviour of the so-called

depletion layer or depletion &one which e'ists at the P- !unction between the

differing semiconductors. (hen a P- !unction is first created, conduction band

"mobile# electrons from the -doped region diffuse into the P-doped region where

there is a large population of holes "places for electrons in which no electron is

present# with which the electrons recombine. (hen a mobile electron recombines

with a hole, the hole vanishes and the electron is no longer mobile. Thus, two



charge carriers have vanished. The region around the P- !unction becomes

depleted of charge carriers and thus behaves as an insulator.

)*++) and )*++ series diodes

The '()**' series "or '()*** series# is a family of popular ).+ amp general

purpose silicon rectifier diodes commonly used in $ adapters for common

household appliances. locking voltage varies from + to )+++ volts. This diode is

made in an a'ial-lead /0-*) plastic package. The '(+)** series is a similarly

popular series for higher current applications, up to 1 $. These diodes come in the

larger /0-2+) a'ial package. These are fairly low-speed rectifier diodes, being

inefficient for s3uare waves of more than ) k4&. The series was second sourced

by many manufacturers. The )*+++ series were in the Motorola Silicon Rectifier

Handbook in )566, as replacements for )26+5 through )26)7. The )*++

series were announced in Electrical Design News in )568, along with the now

lesser known ).-ampere )15) series. These devices are widely used and

recommended. The table below shows the ma'imum repetitive reverse

blocking voltages of each of the members of the )*+++ and )*++

series.



,oltage regulator:&

78+ %oltage regulator

% / %oltage 9egulator /ata :heet ; :pecs

The 78+ provides circuit designers with an easy way to regulate / voltages to

v.

Encapsulated in a single chip;package "I#, the 78+ is a positive voltage /

regulator that has only 1 terminals. They are< Input voltage, =round, 0utput

%oltage. $lthough the 78+ were primarily designed for a fi'ed-voltage output



"%#. 78)2 %oltage regulator )2% / %oltage 9egulator /ata :heet ; :pecs The

78+)2 provides circuit designers with an easy way to regulate / voltages to )2v.

Encapsulated in a single chip;package "I#, the 78+)2 is a positive voltage /

regulator that has only 1 terminals. They are< Input voltage, =round, 0utput

%oltage. $lthough the 78+)2 were primarily designed for a fi'ed-voltage output

")2%#. 78)2 %oltage regulator It is indeed possible to use e'ternal components in

order to obtain / output voltages of< %, 6%, 8%, 5%, )+%, )2%, )%, )8%, 2+%,

2*%. ote that the input voltage must, of course, be greater than the re3uired

output voltage, so that it can be regulated downwards

Capacitor:&

In the 9egulated power supply the rating of the chosen capacitor filter is )+++>?.$

capacitor "originally known as condenser# is a passive two-terminal electrical

component used to store energy in an electric field. The forms of practical

capacitors vary widely, but all contain at least two electrical conductors separated

by a dielectric "insulator#@ for e'ample, one common construction consists of metal

foils separated by a thin layer of insulating film. apacitors are widely used as

parts of electrical circuits in many common electrical devices. (hen there is a

potential difference "voltage# across the conductors, a static electric field develops

across the dielectric, causing positive charge to collect on one plate and negative

charge on the other plate. Energy is stored in the electrostatic field. $n ideal



capacitor is characteri&ed by a single constant value, capacitance, measured in

farads. This is the ratio of the electric charge on each conductor to the potential

difference between them.

The capacitance is greatest when there is a narrow separation between large areas

of conductor, hence capacitor conductors are often called Aplates,A referring to an

early means of construction. In practice, the dielectric between the plates passes a

small amount of leakage current and also has an electric field strength limit,

resulting in a breakdown voltage, while the conductors and leads introduce an

undesired inductance and resistance. apacitors are widely used in electronic

circuits for blocking direct current while allowing alternating current to pass, in

filter networks, for smoothing the output of power supplies, in the resonant circuits

that tune radios to particular fre3uencies, in electric power transmission systems

for stabili&ing voltage and power flow, and for many other purposes.



-esistors:&

$ resistor is a passive two-terminal electrical component that implements electrical

resistance as a circuit element. The current through a resistor is in direct proportion

to the voltage across the resistorBs terminals. Thus, the ratio of the voltage applied

across a resistorBs terminals to the intensity of current through the circuit is called

resistance. This relation is represented by 0hmBs law< where I is the current

through the conductor in units of amperes, % is the potential difference measured

across the conductor in units of volts, and 9 is the resistance of the conductor in

units of ohms. More specifically, 0hmBs law states that the 9 in this relation is

constant, independent of the current. 9esistors are common elements of electrical

networks and electronic circuits and are ubi3uitous in electronic e3uipment.

Practical resistors can be made of various compounds and films, as well as

resistance wire "wire made of a high-resistivity alloy, such as nickel-chrome#.

9esistors are also implemented within integrated circuits, particularly analog

devices, and can also be integrated into hybrid and printed circuits.



The electrical functionality of a resistor is specified by its resistance< common

commercial resistors are manufactured over a range of more than nine orders of

magnitude. (hen specifying that resistance in an electronic design, the re3uired

precision of the resistance may re3uire attention to the manufacturing tolerance of

the chosen resistor, according to its specific application. The temperature

coefficient of the resistance may also be of concern in some precision applications.

Practical resistors are also specified as having a ma'imum power rating which

must e'ceed the anticipated power dissipation of that resistor in a particular circuit<

this is mainly of concern in power electronics applications. 9esistors with higher

power ratings are physically larger and may re3uire heat sinks. In a high-voltage

circuit, attention must sometimes be paid to the rated ma'imum working voltage of

the resistor.

Crystal -.D L.Ds

CE/ is an acronym for Lig/t .mitting Diode. (ell, you ask, what on earth is a

diode. $ diode is a device that, in simplest terms, allows electricity to flow

t/roug/ one way but not t/e ot/er. Those of you who are knowledgeable about

mechanical things could think of it as sort of a check valve. If you have no



mechanical knowledge, disregard that last sentence. ow that you know what a

diode is, an CE/ is !ust one that emits light "ut you could probably figure that out

!ust from reading the name#.

$nother important thing about all CE/Bs "and all diodes# is that every one of them

has e'actly two electrodes. These are important to know when you are wiring an

CE/ into a circuit.

They are the...

0node - The p-side which is the longer leg.

$nd the...Cat/ode - (hich is the n-side and s/orter leg. :ince you know these

terms you can remember that electricity flows easily from the anode to the cathode

but not the other way around.

CE/Bs are great for many reasons. ?irst of all, they donBt heat up like regular light

bulbs do. This is great because, well, you donBt burn yourself. They are also smaller

than a light bulb. $nother important thing about CE/Bs is that they run on very low

amounts of electricity, which is helpful because it makes them safer to work with

"you donBt electrocute yourself#. Most run on about 2+m$.

Dust like with everything, there are some tips that are helpful to make sure your

CE/Bs work well.



Clip t/e leads - :imple, I know, but people forget to. This is important because it

prevents them from bumping into other parts and messing up your circuit.

-emember w/ic/ electrode is w/ic/ - This is a big one because if you donBt it

wonBt work at all. ItBs a diode@ current only flows through it one way.

-ead t/e pacage - :imple again, but each CE/ re3uires slightly differnt voltage

and ampere. It always helps to wire a resistor into your circuit. It will make the

CE/ last longer by dropping the voltage. There are some sites that make it easy to

find which resistor you need. CE/s come in all sorts of si&es as well. 4ere is a

photo showing a 3mm, +mm and '*mm CE/. The AmillimetreA si&e refers to

the diameter of the CE/. ?or e'ample, if you need to drill a hole in a bo' for your

mm blink CE/, the hole si&e should be mm, and youBd need a mm drill bit to

make it. mm are the most common si&e youBll see, and they can be e'tremely

bright Green 3mm, Red 5mm and White 1mm !EDs

• +mm L.Ds can be so bright, they are often used as illumination "lighting

something up, like a flashlight, weBll talk about this ne't#.

• 3mm L.Ds are not as bright but are smaller, and are good

for indication "like an CE/ that tells you something is on#. TheyBre not as good

for illumination because they have a smaller area that is lit.



• '*mm L.Ds are a little rarer, they are huge and chunky but are usually !ust

mm CE/s with a bigger case so they arenBt any brighter. They can be good

indicators but we rarely see them as illuminators.



1IC-2 C2(-2LL.- 4*+'54#C+'

I(-2D6CI2(

The $T85) is a low-power, high-performance M0: 8-bit microcomputer with

*F bytes of ?lash programmable and erasable read only memory "PE90M#. The

device is manufactured using $tmelGs high-density non-volatile memory

technology and is compatible with the industry-standard M:-) instruction set

and pin out. The on-chip ?lash allows the program memory to be reprogrammed

in-system or by a conventional non-volatile memory programmer. y combining a

versatile 8-bit PH with ?lash on a monolithic chip, the $tmel $T85) is a

powerful microcomputer which provides a highly-fle'ible and cost-effective

solution to many embedded control applications.

7eatures

ompatible with M:-)J Products

*F ytes of In-:ystem 9eprogrammable ?lash Memory

K Endurance< ),+++ (rite;Erase ycles

?ully :tatic 0peration< + 4& to 2* M4&

Three-level Program Memory Cock

)28 ' 8-bit Internal 9$M

12 Programmable I;0 Cines



Two )6-bit Timer;ounters

:i' Interrupt :ources

Programmable :erial hannel

Cow-power Idle and Power-down Modes

The $T85) provides the following standard features< *F bytes of ?lash, )28

bytes of 9$M, 12 I;0 lines, two )6-bit timer;counters, five vector two-level

interrupt architecture, a full duple' serial port, on chip oscillator and clock

circuitry. In addition, the $T85) is designed with static logic for operation down

to &ero fre3uency and supports two software selectable power saving modes. The

Idle Mode stops the PH while allowing the 9$M, timer;counters, serial port and

interrupt system to continue functioning. The Power-down Mode saves the 9$M

contents but free&es the oscillator disabling all other chip functions until the ne't

hardware reset.

Pin Configuration



,CC

:upply voltage.

8(D

=round.

Port *

Port + is an 8-bit open-drain bi-directional I;0 port. $s an output port, each pin can

sink eight TTC inputs. (hen )s are written to port + pins, the pins can be used as

high impedance inputs. Port + may also be configured to be the multiple'ed low

order address;data bus during accesses to e'ternal program and data memory. In

this mode P+ has internal pull ups. Port + also receives the code bytes during ?lash



programming, and outputs the code bytes during program verification. E'ternal

pull ups are re3uired during program verification.

Port '

Port ) is an 8-bit bi-directional I;0 port with internal pull ups. The Port ) output

buffers can sink;source four TTC inputs. (hen )s are written to Port ) pins they

are pulled high by the internal pull ups and can be used as inputs. $s inputs, Port )

pins that are e'ternally being pulled low will source current "IIC# because of the

internal pull ups. Port ) also receives the low-order address bytes during ?lash

programming and verification.

Port "

Port 2 is an 8-bit bi-directional I;0 port with internal pullups. The Port 2 output

buffers can sink;source four TTC inputs. (hen )s are written to Port 2 pins they

are pulled high by the internal pullups and can be used as inputs. $s inputs, Port 2


internal pullups. Port 2 emits the high-order address byte during fetches from

e'ternal program memory and during accesses to e'ternal data memory that use

)6-bit addresses "M0%L /PT9#. In this application, it uses strong internal pull-

ups when emitting )s. /uring accesses to e'ternal data memory that use 8-bit

addresses "M0%L 9I#, Port 2 emits the contents of the P2 :pecial ?unction



9egister. Port 2 also receives the high-order address bits and some control signals

during ?lash programming and verification.

Port 3

Port 1 is an 8-bit bi-directional I;0 port with internal pullups. The Port 1 output

buffers can sink;source four TTC inputs. (hen )s are written to Port 1 pins they

are pulled high by the internal pull-ups and can be used as inputs. $s inputs, Port 1


pullups.

-S

9eset input. $ high on this pin for two machine cycles while the oscillator is

running resets the device.

0L.5P-28



$ddress Catch Enable output pulse for latching the low byte of the address during

accesses to e'ternal memory. This pin is also the program pulse input "P90=#

during ?lash programming. In normal operation $CE is emitted at a constant rate

of );6 the oscillator fre3uency, and may be used for e'ternal timing or clocking

purposes. ote, however, that one $CE pulse is skipped during each access to

e'ternal /ata Memory. If desired, $CE operation can be disabled by setting bit +

of :?9 location 8E4. (ith the bit set, $CE is active only during a M0%L or

M0% instruction. 0therwise, the pin is weakly pulled high. :etting the $CE-

disable bit has no effect if the microcontroller is in e'ternal e'ecution mode.

PS.(

Program :tore Enable is the read strobe to e'ternal program memory. (hen the

$T85) is e'ecuting code from e'ternal program memory, P:E is activated

twice each machine cycle, e'cept that two P:E activations are skipped during

each access to e'ternal data memory.

.05,PP

E'ternal $ccess Enable. E$ must be strapped to =/ in order to enable the device

to fetch code from e'ternal program memory locations starting at ++++4 up to

????4. ote, however, that if lock bit ) is programmed, E$ will be internally

latched on reset. E$ should be strapped to % for internal program e'ecutions.



This pin also receives the )2-volt programming enable voltage "%PP# during ?lash

programming, for parts that re3uire )2-volt %PP.

90L'

Input to the inverting oscillator amplifier and input to the internal clock operating

circuit.

90L"

0utput from the inverting oscillator amplifier.

2scillator C/aracteristics

LT$C) and LT$C2 are the input and output, respectively, of an inverting

amplifier which can be configured for use as an on-chip oscillator, as shown in

?igure ). Either a 3uart& crystal or ceramic resonator may be used. To drive the

device from an e'ternal clock source, LT$C2 should be left unconnected while

LT$C) is driven as shown in ?igure 2. There are no re3uirements on the duty

cycle of the e'ternal clock signal, since the input to the internal clocking circuitry

is through a divide-by-two flip-flop, but minimum and ma'imum voltage high and

low time specifications must be observed.

Idle 1ode

In idle mode, the PH puts itself to sleep while all the on chip peripherals remain

active. The mode is invoked by software. The content of the on-chip 9$M and all

the special functions registers remain unchanged during this mode. The idle mode



can be terminated by any enabled interrupt or by a hardware reset. It should be

noted that when idle is terminated by a hard ware reset, the device normally

resumes program e'ecution, from where it left off, up to two machine cycles

before the internal reset algorithm takes control. 0n-chip hardware inhibits access

to internal 9$M in this event, but access to he port pins is not inhibited. To

eliminate the possibility of an une'pected write to a port pin when Idle is

terminated by reset, the instruction following the one that invokes Idle should not

be one that writes to a port pin or to e'ternal memory.

Input5output ports $I52 Ports%

In order to make the microcontroller useful, it is necessary to connect it to

peripheral devices. Each microcontroller has one or more registers "called a port#

connected to the microcontroller pins.

2SCILL02-

Even pulses generated by the oscillator enable harmonic and synchronous

operation of all circuits within the microcontroller. It is usually configured as to

use 3uart&-crystal or ceramics resonator for fre3uency stabili&ation. It can also

operate without elements for fre3uency stabili&ation "like 9 oscillator#. It is

important to say that program instructions are not e'ecuted at the rate imposed by

the oscillator itself, but several times slower. It happens because each instruction is

e'ecuted in several steps. ?or some microcontrollers, the same number of cycles is



needed to e'ecute any instruction, while itBs different for other microcontrollers.

$ccordingly, if the system uses 3uart& crystal with a fre3uency of 2+M4&, the

e'ecution time of an instruction is not e'pected +n:, but 2++, *++ or even 8++ n:,

depending on the type of the microcontroller.

BL2C DI08-01



6S.S 27 1IC-2 C2(-2LL.-S



Cike all good things, this powerful component is basically very simple. It is made

by mi'ing tested and high- 3uality AingredientsA "components# as per following

receipt< The simplest computer processor is used as the AbrainA of the future

system.

/epending on the taste of the manufacturer, a bit of memory, a few $;/ converters,

timers, input;output lines etc. are added $ll that is placed in some of the standard

packages. $ simple software able to control it all and which everyone can easily

learn about has been developed. 0n the basis of these rules, numerous types of

microcontrollers were designed and they 3uickly became manBs invisible

companion. Their incredible simplicity and fle'ibility con3uered us a long time

ago and if you try to invent something about them, you should know that you are

probably late, someone before you has either done it or at least has tried to do it.

The following things have had a crucial influence on development and success of

the microcontrollers<

Powerful and carefully chosen electronics embedded in the microcontrollers can

independently or via input;output devices "switches, push buttons, sensors, C/

displays, relays etc.#, control various processes and devices such as industrial

automation, electric current, temperature, engine performance etc. %ery low prices

enable them to be embedded in such devices in which, until recent time it was not



worthwhile to embed anything. Thanks to that, the world is overwhelmed today

with cheap automatic devices and various NsmartO appliances.

Prior knowledge is hardly needed for programming. It is sufficient to have a P

"software in use is not demanding at all and is easy to learn# and a simple device

"called the programmer# used for NloadingO raedy-to-use programs into the

microcontroller.

0-C;I.C6-. 0(D P-28-011I(8 27 4*+'54#C+'

-ead 2nly 1emory $-21%

9ead 0nly Memory "90M# is a type of memory used to permanently save the

program being e'ecuted. The si&e of the program that can be written depends on

the si&e of this memory. 90M can be built in the microcontroller or added as an

e'ternal chip, which depends on the type of the microcontroller. oth options have

some disadvantages. If 90M is added as an e'ternal chip, the microcontroller is

cheaper and the program can be considerably longer. $t the same time, a number

of available pins is reduced as the microcontroller uses its own input;output ports

for connection to the chip. The internal 90M is usually smaller and more

e'pensive, but leaves more pins available for connecting to peripheral

environment. The si&e of 90M ranges from )2 to 6*F.

-andom 0ccess 1emory $-01%



9andom $ccess Memory "9$M# is a type of memory used for temporary storing

data and intermediate results created and used during the operation of the

microcontrollers. The content of this memory is cleared once the power supply is

off. ?or e'ample, if the program perform an addition, it is necessary to have a

register standing for what in everyday life is called the NsumO. ?or that purpose,

one of the registers in 9$M is called the AsumA and used for storing results of

addition. The si&e of 9$M goes up to a few Fs. Electrically Erasable

Programmable 90M "EEP90M# The EEP90M is a special type of memory not

contained in all microcontrollers. Its contents may be changed during program

e'ecution "similar to 9$M #, but remains permanently saved even after the loss of

power "similar to 90M#. It is often used to store values, created and used during

operation "such as calibration values, codes, values to count up to etc.#, which must

be saved after turning the power supply off. $ disadvantage of this memory is that

the process of programming is relatively slow. It is measured in mili seconds.

Special 7unction -egisters $S7-%

:pecial function registers are part of 9$M memory. Their purpose is predefined by

the manufacturer and cannot be changed therefore. :ince their bits are physically

connected to particular circuits within the microcontroller, such as $;/ converter,

serial communication module etc., any change of their state directly affects the

operation of the microcontroller or some of the circuits. ?or e'ample, writing &ero



or one to the :?9 controlling an input;output port causes the appropriate port pin

to be configured as input or output. In other words, each bit of this register controls

the function of one single pin.

Program Counter

Program ounter is an engine running the program and points to the memory

address containing the ne't instruction to e'ecute. $fter each instruction e'ecution,

the value of the counter is incremented by ). ?or this reason, the program e'ecutes

only one instruction at a time !ust as it is written. 4oweverthe value of the

program counter can be changed at any moment, which causes a N!umpO to a new

memory location. This is how subroutines and branch instructions are e'ecuted.

$fter !umping, the counter resumes even and monotonous automatic counting Q),

Q), Q).

I(.-70CI(8 2 .9.-(0L 1.12-<

The number of bits that a semiconductor memory chip can store is called chip

capacity

). It can be in units of Fbits "kilobits#, Mbits "megabits#, and so on

2. This must be distinguished from the storage capacity of computer systems1. (hile the memory capacity of a memory I chip is always given bits, the

memory capacity of a computer system is given in bytes

*. )6M memory chip K )6 megabits

. $ computer comes with )6M memory K )6 megabytes



Memory chips are organi&ed into a number of locations within the I. Each

location can hold ) bit, * bits, 8 bits, or even )6 bits, depending on how it is

designed internally. The number of locations within a memory I

depends on the address pins. The number of bits that each location can hold is

always e3ual to the number of data pins.

0ne of the most important characteristics of a memory chip is the speed at which

its data can be accessed. To access the data, the address is presented to the address

pins, the 9E$/ pin is activated, and after a certain amount of time has elapsed, the

data shows up at the data pins. The shorter this elapsed time, the better, and

conse3uently, the more e'pensive the memory chip. The speed of the memory chip

is commonly referred to as its access time.

In connecting a memory chip to the

PH, note the following points

). The data bus of the PH is connected directly to the data pins of the

memory chip

2. ontrol signals 9/ "read# and (9 "memory write# from the PH are

connected to the 0E "output enable# and (E "write enable# pins of the

memory chip1. In the case of the address buses, while the lower bits of the address from the

PH go directly to the memory chip address pins, the upper ones are used to

activate the : pin of the memory chip

*. $CE "address latch enable# pin is an output pin for 8+)



- $CE R +, P+ is used for data path

- $CE R ), P+ is used for address path

LI=6ID C-<S0L DISPL0< $LCD%:

$ li3uid crystal display "C/# is a flat panel display, electronic visual display or

video display video display that uses the light modulating properties of li3uid

crystals. Ci3uid crystals do not emit light directly.



C/s are available to display arbitrary images "as in a general-purpose computer

display# or fi'ed images which can be displayed or hidden, such as preset words,

digits, and 7-segment displays as in a digital clock They use the same basic

technology, e'cept that arbitrary images are made up of a large number of

small pi'els, while other displays have larger elements. It looks almost like the one

shown below. $s we can see that there are 8 data pins along with 1 control pins.

0ne ground and two power pins are also there.

'>9" c/aracter LCD

C/ is preferred in comparison to led since we can display a limited no. of

characters using led moreover led must be refreshed by the cpu to keep displaying

the data.

Pins 7unctions<



PI( D.SC-IPI2(:

PI( (61B.- S<1B2L 76(CI2(

) ,ss =/

2 %dd Q 1% or Q %

1 %o ontrast $d!ustment

* 9: 9egister :elect :ignal

9;( 9ead;(rite :ignal

6 E Enable :ignal

7 /+ /ata us Cine

8 /) /ata us Cine

5 /2 /ata us Cine)+ /1 /ata us Cine

)) /* /ata us Cine

)2 / /ata us Cine

)1 /6 /ata us Cine

)* /7 /ata us Cine

) %EE Q *.2% for

CE/;egative %oltage

0utput

)6 =nd =/



The C/ consists of )6 pins out of which 2 are used for backlight. ontrast on

display depends on the power supply voltage and whether messages are displayed

in one or two lines. ?or that reason, variable voltage +-%dd is applied on pin

marked as %ee. Trimmer potentiometer is usually used for that purpose. :ome

versions of displays have built in backlight "blue or green diodes#. (hen used

during operating, a resistor for current limitation should be used. The read write

pin is ground while using the universal kit.

LCD Basic Commands

$ll data transferred to C/ through outputs /+-/7 will be interpreted as

commands or as data, which depends on logic state on 9: and E pin<

-S ? ' - its /+ - /7 are addresses of characters that should be displayed. .( is

high to low.

-S ? * - its /+ - /7 are commands which determine display mode.to low .( is

high.



122- D-I,.- L"#3D:

The C251 and C251/ are 3uadruple high-current half-4 drivers. The C251 is designed to provide bidirectional drive currents of up to ) $ at voltages from *. % to 16 %. The C251/ is designed to

provide bidirectional drive currents of up to 6++-m$ at voltages from *. % to 16 %. oth

devices are designed to drive inductive loads such as relays, solenoids, dc and bipolar steppingmotors, as well as other high-current;high-voltage

loads in positive-supply applications. $ll inputs are TTC compatible. Each output is a complete

totem-pole drive circuit, with a /arlington transistor sink and a pseudo-/arlington source./rivers are enabled in pairs, with drivers ) and 2 enabled by ),2E and drivers 1 and * enabled

by 1,*E.

(hen an enable input is high, the associated drivers areenabled and their outputs are active and in phase with their inputs. (hen the enable input is low,those drivers are disabled and their outputs are off and in the high-impedance state. (ith the

proper data inputs, each pair of drivers forms a full-4 "or bridge# reversible drive suitable for

solenoid or motor applications. 0n the C251, e'ternal high-speed output clamp diodes should beused for inductive transient suppression. $ %) terminal, separate from %2, is provided for

the logic inputs to minimi&e device power dissipation.

The C251and C251/ are characteri&ed for operation from +elsius to 7+elsius.

7.06-.S:

• (ide :upply-%oltage 9ange< *. % to 16 %

• :eparate Input-Cogic :upply

• Internal E:/ Protection



• Thermal :hutdown

• 4igh-oise-Immunity Inputs

• 0utput urrent ) $ Per hannel "6++ m$ for C251/#

• Peak 0utput urrent 2 $ Per hannel ").2 $ for C251/#

• 0utput lamp /iodes for Inductive

• Transient :uppression "C251/#

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