Part Number: LM339
I am using an LM339 in conjunction with a 4401 transistor to control a FET.
I have started to see a rash of FET failures and have been able to make the circuit work and/or fail by changing the LM339.
The part markings on all the sample assemblies that fail are 'TI LM339' and 'HYC5392H'.
The markings on the sample assemblies that work are a mixture:
LM339 G4 and 9CADSVM
LM339 and 16P18NAG4
LM339 and 05P042AG3
LM339 G4 and 04ALFDM
What has changed?
Can you provide the exact part number you are ordering (Assuming LM339D or PW).
Can you also provide a schematic that shows both the input signal source and output loads? What is the FET driving?
Low Power Amplifiers and Comparators (LPAC) Applications
In reply to Paul Grohe:
My parts list calls out LM339D.
I inserted a pdf of the schematic, but I don't think it worked properly. If not is there a convenient way to send you a pdf?
P1-2: Analog input creates xx% duty cycle at FET (above 9v = 100%, below 1v = 0%)
Failing output is connected to a solenoid.
In reply to Brian Mix:
The LM339 does not get damaged. Q2 overheats and fails (open). We can monitor and see the temperatures start to rise and shut down before failure occurs. We use this method to stop running before failure and then change the LM339. We can make a good assembly fail, and a failing assembly good, by swapping the LM339.These assemblies are built for us by Global Point in China, getting pic's of the reel may be difficult.Picture of top of failing LM339, blow-up of TI Logo, and bottom of IC attached.
It is OK to contact me directly via my email.
You have come to the same conclusions that we have. The "bad" LM339 is causing the FET to switch many times each time it should switch once. I can make the changes and tests you suggest, but we get the same results removing these parts would give by setting the input above 9v. At this input, the LM339 sees only one transition on its inputs so the FET comes on and stays on. In this configuration (as long as the load is small enough for the FET to run 100% duty cycle) the boards will run OK.
I will contact you directly.
Thanks for all your help, Paul.
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