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I am using an L293DD Dual H-Bridge IC to power my DC motors. I have realized I am using inadequate heatsinks, and 1,5 times the nominal maximum current(1,8A instead of 1,2A), but the circuit is working.

The datasheet says, that this IC has overtemperature protection, but doesn't mention exact data.

My question is, can I rely on its overtemperature protection? I don't mind if the IC shuts down, when I overdrive it, but when it cools down, it should start working again.

Note: This is a prototype, I know its horrible practice, Still I want to know what can I expect, perhaps understand what is going on in more depth.

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  • \$\begingroup\$ @m.Alin I am an amateur and failed to check that my DC motor is way above specs. Yet it works, drawing spiking 2A currents. My question is whether I can rely on the temperature protection.(Obviously lifetime will suffer and such, but it would be good to know what can I expect) \$\endgroup\$
    – akaltar
    Commented Feb 12, 2016 at 20:32
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    \$\begingroup\$ We seem to have different understandings of what "works" means for a circuit. \$\endgroup\$
    – PlasmaHH
    Commented Feb 12, 2016 at 20:34
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    \$\begingroup\$ Nothing that I would ever count on for normal operation \$\endgroup\$
    – PlasmaHH
    Commented Feb 12, 2016 at 20:42
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    \$\begingroup\$ The fact that the 'overvoltage temperature' is mentioned only on the fist page of the datasheet (written probably by the marketing department) with no mentions of any specifications should hint to you that it's not reliable at all.. \$\endgroup\$
    – m.Alin
    Commented Feb 12, 2016 at 20:43
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    \$\begingroup\$ The IC has a Tj spec of up to 150C. So somewhere above 150C Tj, the circuit would shutdown. One way to look at this may be: somewhere between the smell of burning electronics and the IC unsoldering itself, the circuit should shutdown. \$\endgroup\$
    – rioraxe
    Commented Feb 13, 2016 at 0:55

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The answer is, if you want a good design, then NO. You can't rely on over temp protection. Whenever you go beyond the specs in the datasheet especially the maximum ratings all bets are off. The engineers designed this part with 1.2Amps in mind and also tested it with 1.2Amps. You don't know why they did this. Maybe they had 1 out of 100 blow up when they tested it beyond 1.2 Amps, maybe they hit 90C and 1.2Amps and then they start to die. maybe its just an intermittent problem. You could be running your chip and it could fail at any time. This question is like saying can I run my car engine at 7000RPM if the red line is at 6000RPM? Yes you can, do you want to no probably not.

There are a few ways you may be able to overcome this problem. If your worried about an overtemp condition, put a heatsink on it. Even a piece of aluminum that is 2 or 4 times more area than the IC can help drive the temperature down by 10's of degrees.

You can parallel the devices and half the current going through the IC. Usually this works with TTL and BJT which is what the drivers say they are.

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