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THS4524-EP: Amplifier IC Malfunctioning with Differential Probe

Balasubramanian Srikanthan
Prodigy 20 points
Part Number: THS4524-EP
Other Parts Discussed in Thread: THS4524

Hello,

I am an R&D Electrical Engineer at Johnson & Johnson Vision. In one of our projects, we use THS4524 as a unit gain Differential buffer before ADC. When I tried to probe the output of the THS4524 with a Tektronix TDP1500 Differential probe, I saw that after continuous use of about an hour or so, the IC was malfunctioning on three different PCBAs. By malfunctioning, the IC output is either oscillating continuously or much lesser than the input voltage (but it is unity gain) and also affects the common voltage from the ADC.

I am attaching a snapshot of one of the channels of the Buffer used with the probing locations highlighted:

Please let me know if there are known issues with sensitivity or other possible causes for similar damage. And do let me know if you have any questions.

Thank you.

  • 0
    TI__Mastermind 26855 points

    Hello Balasubramanian, 

      Thank you for the introduction and for the information. 

      A few questions:

    1. Are all channels on the device oscillating/lower output than expected?
    2. Does the failing device show no oscillation when removing input then powering off and on the device? As in is it only occurring after continuous use or when the device fails, it continues to fail? 
    3. Also, what are the supplies to the device (in terms of kind and value)? 

      A quick simulation of the circuit shows stability, but try increasing the output resistors (R190 and R468) to 50 ohms for the devices that are failing and re-view the continuous output.

    Thank you,

    Sima

  • 0
    Prodigy 20 points

    Hello Sima,

    Thank you for the response.

    1. I observed this behavior only in the channel that I probed. This happened for all three boards that I tested.

    2. Removing the probe or restarting the power did not fix the issue. Once this occurs, the issue persists.

    3. The IC is powered by 5V from a 12 to 5V Buck converter - TPS54521RHLR

    I will try the simulation you mentioned and get back to you. 

    Thank you,

    Bala

  • 0 in reply to Balasubramanian Srikanthan
    TI__Mastermind 26855 points

    Hello Bala,

      Thank you for the additional information. I would suggest to check or monitor the power supply to the device from the buck converter. After increasing the output resistors, can you share a scope shot of the output? Also, what is the input range to the device and the output range you are seeing? 

    Thank you,
    Sima