Page 56 - CNC Robotics

Chapter 2 / Electronics

APPLICATION NOTE
Forbipolarrnotorswithwinding currentsupto2Athe THE L298N AND L293E
L297 should be used with the L298N ; for winding Sincethe L297 is normally used with an L29BNor
currents up to 1Athe L293E is recommended (the L293Ebridgedrivera brief review of these devices
L293will alsobe useful ifthe chopperisn't needed). will makethe rest of this note easierto follow.
Highercurrentsareobtained withpowertransistors The L29BN and L293E contain two bridgedriver
or darlingtons and for unipolar motors a darlington stages,eachcontrolledbytwoTIL-level logicinputs
array such as the ULN20758 is suggested. The anda TIL-levelenableinput.Inaddition,theemitter
blockdiagram,figure 1, showsa typicalsystem.
connectionsof the lowertransistorsarebroughtout
to externalterminalsto allow the connection of cur-
Applicationsof the L297 can be foundalmosteve- rent sensingresistors (figure 2).
I· rywhere...printers(carriageposition,daisyposition,
paper feed , ribbon feed), typewriters, plotte rs, nu- Forthe L29BN SGS' innovativeion-implanted high
merically controlled machines, robots, floppy disk voltage/highcurrent technologyis used,allowingit
drives, electronicsewing machines, cash registers, to handleeffectivepowersup to 160W(46V supply,
photocop iers, telex machines, electronic carbure- 2A per bridge).A separate 5V logic supply input is
tos, telecopiers, photographic equipment, paper providedto reduce dissipationand to allow direct
tape readers,opticalcharacterrecognisers, electric connectionto the L297 or other controllogic.
valves and so on. In this note the pinsof the L29BNare labelledwith
the pin namesof the correspondingL297terminals
TheL297 is madewith SGS' analog/digitalcompa- to avoidunnecessaryconfusion.
2
tible r L technology(like Zodiac)and is assembled The L29BNis suppliedina 15-lead Multiwattplastic
in a 20-pinplastic DIP. A 5V supply is used and all powerpackage. It's smallerbrother,the functionally
signal lines areTTUCMOScompatibleor opencol- identicalL293E,ispackagedina Powerdip- acop-
I- lectortransistors.High density is one of the keyfea- perframe DIP that usesthe fourcenter pinstocon-
tures of the technology so the L297 die is very duct heatto the circuit boardcopper.
compact.
Figure 2 : TheL29BNcontainstwo bridge drivers (four pushpull stages)eachcontrolledby two logic
inputs and an enableinput. Extemal emitterconnectionsareprovided for currentsense
resistors. The L293E has externalconnectionsfor all four emitters.

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