AD8556 Evaluation board is not working

Hello ,

I have purchased sdp - s board and evaluation board AD8556 programmable gain signal amplifier .

I have downloaded user manual of evaluation board from following  analog devices website

http://www.analog.com/static/imported-files/eval_boards/AD8556-EVAL.pdf

I have followed basic initial setup steps as per user manual but it is not working .

The steps which i have followed is

1. Connect the AD8556-EVALZ evaluation board to the SDP board, which is connected to the USB port of your PC system using USB mini-B cable.

2. Position manual switches to VPOS P2 and VNEG P1.

3. Jumper the VCLAMP connector pin to the VDD connector pin.

4. Apply 1 mV dc signal between the +VIN dc and −VIN dc connectors, and monitor the VOUT dc output using a voltmeter.

5. Place an AD8556-EVALZ part in the SOIC socket, connect the VCLAMP pin to the VDD pin, and apply dc power to the board using an external power supply (±2.5 V).

Expected = When you complete this procedure, the output should be 70 mV, with the board in this configuration consuming roughly 4 mA.

but when I complete this procedure it gives output 1.55 v instead of expected 70mV .

can anyone suggest what will be the issue with this eval board  ???

Thanks and Regards

Dipak Khairnar

AD8556-EVAL.pdf
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  • 0
    •  Analog Employees 
    on Feb 18, 2014 10:44 PM

    Hi Dipak,

    Apology for late response.

    I have evaluated the board and it seems that there was some mistake on the instructions. Instructions 2 say that the switches should be position to VPOS P2 and VNEG P1. In this configuration the input pins DUT IN - and DUT IN+ will be shorted while the amplifier will only see for the difference between its inputs.

    You can position the switches on this combination: VPOS P1 and VNEG P1 or VPOS P2 and VNEG P2.

    Another thing is that before the  initial hardware setup and output verification you should adjust for differential input offset.

    Let me know if this will work.

    Thanks!

    Philip

  • Hi Philip,

    unluckily, I also experienced some difficulties in getting the system working. Thanks for the corrected switch positions you mentioned before.

    The prior notice "Adjusting for 0 V differential input" in the data sheet seems to have no information about the two switches. Any idea?

    Secondly, the sheet says, I should monitor the output voltmeter at the V_OUTDC pin. Am I right the voltmeter should read 0 V? I got V_SS = -2,5 V.

    Missing information on JP3 and JP2:

    Neglecting JP3 and JP2, I experienced quite high currents on my +-2,5 V, when connecting to the µC board. The data sheet does not stress the issue of using power from the attached µC board while attaching external power to the pins VDD, GND, and VSS. And how about using +5 V to GND?

    I assume open JP2 and JP3, then connect the µC board. Finally attach external +-2,5 V and GND. Bringing the AD8556-EVALZ is not so easy for beginners. ;-)

    Any advice is appreciated! Please let me know.

    Camfix

Reply
  • Hi Philip,

    unluckily, I also experienced some difficulties in getting the system working. Thanks for the corrected switch positions you mentioned before.

    The prior notice "Adjusting for 0 V differential input" in the data sheet seems to have no information about the two switches. Any idea?

    Secondly, the sheet says, I should monitor the output voltmeter at the V_OUTDC pin. Am I right the voltmeter should read 0 V? I got V_SS = -2,5 V.

    Missing information on JP3 and JP2:

    Neglecting JP3 and JP2, I experienced quite high currents on my +-2,5 V, when connecting to the µC board. The data sheet does not stress the issue of using power from the attached µC board while attaching external power to the pins VDD, GND, and VSS. And how about using +5 V to GND?

    I assume open JP2 and JP3, then connect the µC board. Finally attach external +-2,5 V and GND. Bringing the AD8556-EVALZ is not so easy for beginners. ;-)

    Any advice is appreciated! Please let me know.

    Camfix

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