ADA4528-2ACPZ exposed pad

Hi, I am using ADA4528-2ACPZ in a design where The exposed pad has been connected to ground. Data sheet suggest connecting the pad to V- or to leave it opened. The circuit is simply used as a buffer (non inverting gain 1). However the input voltage is attenuated at its output to +/- 40mV peak. In put is +1V peak sinewave with frequencies swept from 1 to 1000Hz.

I have got the ground connecting vias disconnected (by pcb manufacturer using back-drilling technique used on high speed pcb designs). The results is the same. The power rails are +/- 2.5V.

Could the cip be damaged?

With thanks and regards, Vic

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  • Hi Donnie, It happens that the output is run through :Coaxial Connectors Micro Switch PCB Strt Jack Surf Mnt 50 ohm (Amphenol 902-9235), thus the measurement has been done without a load or in situ with 8k resistor connected to ADA4528 amplifier as part of LPF. Checked out the resistivity path to ground and is about 40K. Kind regards, Vic

  • 0
    •  Analog Employees 
    on Jun 11, 2020 11:17 AM 7 months ago in reply to Vic

    Hi Vic,

    Could you try probing the outputs of the ADA4528 directly? The attenuation could be a result of an impedance mismatch between the PCB coaxial jack and the scope/measuring equipment that you're using.

    If you could provide a sample schematic or connection diagram between the ADA4528 and the measuring equipment you're using then that would greatly help.

    Thanks,

    Donnie

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  • 0
    •  Analog Employees 
    on Jun 11, 2020 11:17 AM 7 months ago in reply to Vic

    Hi Vic,

    Could you try probing the outputs of the ADA4528 directly? The attenuation could be a result of an impedance mismatch between the PCB coaxial jack and the scope/measuring equipment that you're using.

    If you could provide a sample schematic or connection diagram between the ADA4528 and the measuring equipment you're using then that would greatly help.

    Thanks,

    Donnie

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