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PGA113: Noise generation at shock/vibration

Azamat Agzamov
Prodigy 20 points
Part Number: PGA113

Good day. We have some issues with programmable gain amplifier PGA113. The circuit block of this IC starts to generate noise as the PCB takes shock or vibration. Amplitude of noise depends on impact force and on some level have its maximum from AVDD (+5V) to GND.

VOCM is +2.5 Volts. JMP2 not used. мкФ - uF, Ом - Ohm. VOCM buffered by AD8616ARZ. Also we've tryied to use Vref from MSP430F2619SPM instead of VOCM.

Shock waveform at 2V/10 ms div.

  • 0
    TI__Guru 52696 points

    Hello Azamat,

    What type of capacitor are you using for C3 and C6 on your circuit above?

    Most dielectrics of multi-layer ceramic capacitors exhibit a piezoelectric effects than can cause unexpected signals; when vibrations created on the board can create electrical signals within the ceramic capacitor.  The piezoelectric effect is the creation of a voltage due to an applied mechanical stress. Please see attached blog note: "Stress-induced outbursts: Microphonics in ceramic capacitors (Part 1)"

    A possible solution is to use a different type of capacitors, for example, aluminum, al-polymer, film capacitors, as this piezoelectric effect is unique to ceramic.

    Thank you and Regards,

    Luis

  • 0 in reply to Luis Chioye
    Prodigy 20 points

    Yes, this is X7R ceramic capacitors. We thought about these yesterday too. Probably this is the most reasonable cause. 

    Thank you for participation.