ULN2003 warning

Thread Starter

Ian0

Joined Aug 7, 2020
9,667
I bet everyone uses the good old ULN2003, as old as the hills, was it Sprague or Unitrode?
I think the reason for its existence was to drive 24V relays, and it is generously rated at 50V 500mA
Beware - there’s a newcomer on the scene, under the Diodes brand and it’s only rated at 20V.
It blows up on a 24V supply.
Now Diodes does some good stuff, especially the old Zetex (formerly Ferranti) transistors. By all means make a Darlington arrays but don’t call it ULN2003 then rate it at 20V, even with an extra suffix hidden in the part code.

Now after spending all morning searching for the fault, I’ve got two dozen to unsolder. . . .
 

Ya’akov

Joined Jan 27, 2019
9,069
It seems passing strange they would use the number of a jellybean part and not at least match the absolute maximum ratings.
 

eetech00

Joined Jun 8, 2013
3,856
I bet everyone uses the good old ULN2003, as old as the hills, was it Sprague or Unitrode?
I think the reason for its existence was to drive 24V relays, and it is generously rated at 50V 500mA
Beware - there’s a newcomer on the scene, under the Diodes brand and it’s only rated at 20V.
It blows up on a 24V supply.
Now Diodes does some good stuff, especially the old Zetex (formerly Ferranti) transistors. By all means make a Darlington arrays but don’t call it ULN2003 then rate it at 20V, even with an extra suffix hidden in the part code.

Now after spending all morning searching for the fault, I’ve got two dozen to unsolder. . . .
Hardly worth using those anymore with available Mosfet arrays...
 

Thread Starter

Ian0

Joined Aug 7, 2020
9,667
The offending one is a MOSFET device, rated at 20V 140mA instead of 50V 500mA, and it’s no cheaper!
Even used within its ratings, I know which one my money is on for being the most reliable - the one that’s been doing it’s job for 40 years!

Because it is a 7 device array, could it originally have been a dot matrix printer hammer driver?
 

Ya’akov

Joined Jan 27, 2019
9,069
The offending one is a MOSFET device, rated at 20V 140mA instead of 50V 500mA, and it’s no cheaper!
Even used within its ratings, I know which one my money is on for being the most reliable - the one that’s been doing it’s job for 40 years!

Because it is a 7 device array, could it originally have been a dot matrix printer hammer driver?
That does make sense. Nothing else immediately jumps out matching applications as well as a 5x7 dot matrix printer.
 

Lo_volt

Joined Apr 3, 2014
316
...not at least match the absolute maximum ratings.
MAX232A comes to mind for me. In the early '90s Analog Devices made a pin compatible part that was not electrically compatible. The Maxim part was able to use 0.1uF caps for the voltage multiplier, but the Analog Devices part would only work with 10uF parts. I got stung by this when an assembly house used the AD devices. Fortunately they admitted their mistake and replaced the parts on their own dime.

It's also the main reason I check the specs before buying alternative brands.
 

Thread Starter

Ian0

Joined Aug 7, 2020
9,667
I have to admit that it was the sheer longevity of the device allowed me to get fooled. It’s been 50V 500mA for more than forty years. Who would expect it suddenly to be 20V 140mA?
 

Audioguru again

Joined Oct 21, 2019
6,672
They should be jailed for using a standard part number on a part with completely different specs.
Whatsamatter with Diodes Inc? I hope they don't do that with other common ICs or transistor parts.
 

eetech00

Joined Jun 8, 2013
3,856
The offending one is a MOSFET device, rated at 20V 140mA instead of 50V 500mA, and it’s no cheaper!
Even used within its ratings, I know which one my money is on for being the most reliable - the one that’s been doing it’s job for 40 years!

Because it is a 7 device array, could it originally have been a dot matrix printer hammer driver?
Well….ULN2003 is a Darlington device.
Was there a mixup?
 

nsaspook

Joined Aug 27, 2009
13,079
Well….ULN2003 is a Darlington device.
Was there a mixup?
The mixup is from someone either not thinking about human nature or abusing human nature to sell parts. I agree the part should not be called ULN2003xxx because we make logical assumptions from long term mental patterns that our brains use to reduce clutter. The instant we see ULN2003 decades of mental patterns see only the Darlington device while our brains quickly toss the extra suffix to the trash bin.
 

eetech00

Joined Jun 8, 2013
3,856
The mixup is from someone either not thinking about human nature or abusing human nature to sell parts. I agree the part should not be called ULN2003xxx because we make logical assumptions from long term mental patterns that our brains use to reduce clutter. The instant we see ULN2003 decades of mental patterns see only the Darlington device while our brains quickly toss the extra suffix to the trash bin.
Understood.....

I use the TI version TPL7407L.
 
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