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ULN2003A: Device burned

Part Number: ULN2003A

Hi all:

     We have recently delivered a batch of products and found that a small part of the ULN2003A chip of the control relay may cause plate burning, which is quite serious. The unified part is the com foot of ULN2003A (the 9th foot of the chip burns out).We have done some destructive experiments, but did not restore this situation.

Would you please help to analyze under what circumstances the chip will burn down?

Thank you!

11 pin output waveform in normal operation:

Normal working 10-pin output waveform:

PCB placement:

  • Hi Timsen, 

    Thanks for reaching out on E2E!

    I'd like to get a better understanding of the system and clarify a few conditions:

    1. What are your operating conditions? When does the device fail, during startup or DC conditions? What is the current drawn from each channel?
    2. Do you have any oscilliscope shots or waveforms you can share?
    3. Can you share the layout of the ULN2003A and the surrounding devices? 
    4. Is the COM pin connected to the input voltage as the loads?
    5. Does replacing the device fix the issues such that the system works properly afterwards? It looks like a lot of the surrounding devices were also damaged, are you able to replicate the issue with the other devices disconnected?

    Thanks,

    Arthur Huang

  • Hi Arthur:
    1. ULN2003A chip is used to control relay output, and low level control relay coil is output after MCU gives control signal.The circumstances of the failure are unknown.According to the specification of relay, the maximum current of each channel is about 80mA in normal operation.
    2. 11 pin output waveform in normal operation: The attached figure cannot be added
    3.The attached figure cannot be added
    4.The COM port is S12V connected to the relay power supply (note: the relay control power supply is isolated from the output power supply).
    5.Some of them were only slightly burnt out by ULN2003. After we replaced ULN2003, the products returned to normal work (note: some of them will even break through the IO port of MCU).
    Only the relay has relatively large interference around, and EMC interference cannot be excluded. What we control externally is the car window. The normal operating current is 2~3A, and it will not work for a long time.The maximum instantaneous current is about 13A.There are no high-power heating elements around.
  • Hi Arthur:
    2.It's on top
    3.It's on top

    Thank you!
  • Hi Timsen, 

    Can you attach any current probes to the oscilloscope shots? I'd like to get a better understanding on the current spikes during PWM. My guess is that the inductive kickback through the flyback diode of the ULN2003a is too much and causing the diode to fail. You could also try connecting an external flyback diode to help dissipate the inductive kickback.

    Thanks,

    Arthur Huang

  • Hi Timsen,

    I wanted to follow up on this thread. Have you been able to fix the device? If so, I will close this thread.

    Thanks,
    Arthur