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MAX3243E: Waveform issue

ian wu
Intellectual 905 points

Part Number: MAX3243E

hi expert

During the operation of MAX3243E, the waveform level of the Driver output signal is abnormal. As shown in the left figure below, it is a normal waveform, and the right figure below is an abnormal waveform. Please help confirm whether the waveform in the right figure is risky.

Waveform .pptx 

What are the main causes of the waveform shown in the right picture

  • 0
    TI__Mastermind 19202 points

    Hi Ian,

    Can you share a schematic?

    What are the differences between the waveforms? Is there a device difference or setup difference?

    From a communication perspective, it is not a problem as it is still above 3V. The receiver will still be able to interrupt this as a valid dominant signal. 

    My first guess is that the voltage supply is having issues. If the charge pump capacitors for the MAX3243E are not set up correctly, it will lead to voltage issues. If you could send me the schematic, I can verify this. 

    Best,

    Ethan

  • 0 in reply to Ethan Sempsrott
    Intellectual 905 points

    Thanks for your reply.

     

    As you said, the reason is using an unproper value cap for C1 charge pump. The datasheet recommands a 0.33uF or 0.47uF for 5V VCC condition. Our design uses a 0.1uF cap(C159) as the following picture shown:SCH.pptx

    After correcting the cap's value, the irregular waveform recovered. But, if I remain the 0.1uF cap, will it reduce the lifetime or impact the status of MAX3243E for a long period working?

  • 0 in reply to ian wu
    TI__Mastermind 19202 points

    Hi Ian,

    We strongly recommend using the proper capacitor values. Otherwise, we cannot fully provide you with our support since you are operating outside the recommended datasheet conditions. 

    We have not specifically tested with improper cap values so I cannot say exactly what will happen. There is a chance that this will accelerate the device lifetime.

    Best,

    Ethan