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Maximum Ratings Operating ConditionsAccording to the L293 Datasheet, the Maximum Supply Voltage(VCC1)(supply for internal logic translation) is 36V. It is also mentioned that Max Input Voltage(V1)=7V whereas the Max High Level Input Voltage(VIH) is VCC1.

  • If my supply to VCC1 is 12V. Will a 12V HIGH logic Level(i.e. Logic HIGH= 12V; Logic LOW=0V) given to the logic pins(1A,2A,3A,4A) damage the IC?
  • When no motor is connected to the L293D, how much current does the IC draw alone?
  • I am aware of the fact that the L293D dissipates heat through its GND pins(GND plane).Will a Heatsink placed on top of the DIP package of the L293D dissipate heat efficiently?
Jonathan Pereira
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2 Answers2

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  • Yes. As you will be exceeding the absolute maximum ratings for the chip. It would not die instantly but will, eventually. If your main control signal is 12V, you can use a resistor voltage divider to feed Vi respecting the maximum rate.
  • Well, the best is measuring with a multimeter. Anyway, you can estimate it by looking the table at "6.5 Electrical Characteristics". It depends on the state of the pins.
  • It will dissipate heat efficiently as long you calculate what heat sink you must use accordingly "6.4 Thermal Information". https://en.wikipedia.org/wiki/Heat_sink#Thermal_resistance
Rodrigo N. Hernandez
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"If my supply to VCC1 is 12V."

That means you are using the chip outside it recommended operating consditions, which means that the manufacturer does not guarantee that it fulfills the functions described in the datasheet. (But you are within the absolute maxima, so the manufacturer guarantees that the chip will not immediately be damaged.)

"Logic HIGH= 12V"

That exceeds even the absolute maxima, so the manufacturer doesn't even guarantee that the chip will survive this.

"how much current does the IC draw alone?"

Check the datasheet!

enter image description here

Will a Heatsink placed on top of the DIP package of the L293D dissipate heat efficiently?

Did I mention "read the datasheet"?

enter image description here

Apparently using the top instead of the gnd pins adds 6 C/W, and to that you must add the thermal contact resistance between the package and your heatsink. (And then add the heatsink itself, but that would also be the case if you used the GND pins.) Whether you think of this as "efficient" is up to you.

Wouter van Ooijen
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  • So basically the maximum High-Level Input voltage can be 7V if VCC1 ≥ 7 V. And it is recommended that VCC1 should be less than 7V. – Jonathan Pereira Oct 21 '16 at 10:57
  • VCC1 =< 7V is both required for normal operation AND for survival. There is often some margin between these two but not in this case. – Wouter van Ooijen Oct 21 '16 at 11:02
  • I am connecting the output pins(1,7) of LM324 to the L293D's logic Input pins(2,7). The output of the LM324 is 10.57V & the recommended operating voltage of the L293D is <7V. What should be the value of resistance that should be used. – Jonathan Pereira Oct 22 '16 at 02:33
  • Use resistor dividers that keep the L293's input within the allowed range, and satisfy the input current requirements as shown in the datasheet 6.5 snippet, and keep the currents within the LM324's output limit. Yes, that requires some calculations. – Wouter van Ooijen Oct 22 '16 at 09:10