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Question about the PGA281EVM

user6513054
Prodigy 10 points
Part Number: PGA281EVM
Other Parts Discussed in Thread: PGA281

We have a Texas Instruments PGA281EVM module. During each measurement the LED (error) lights up. Everything is powered by +/- 15V (J5, J10, J9). During the initial tests, we connected +15V to TP1, 10 ohm resistor between TP1 and TP4, 1 kilo ohm resistor between TP4 and ground. At the output of the amplifier, we observed voltage changes depending on the set gain (although not in accordance with the gain ratio). When +15V voltage is not applied to TP1 then the LED goes out. Please help us solve this problem.

Kind regards,
Pawel

  • 0 in reply to kai klaas69
    TI__Guru 54396 points

    HI Pawel,

    When you connect TP1 (INP) of the PGA281 to the +15V supply, the input of the instrumentation amplifier is outside the allowed input voltage range. 

    Both (INP) and (INN) PGA281 inputs must remain inside the allowed input range, which is at least 2.5 Volts from the VSP/VSN supply rails.  As Kai has highlighted, the PGA281 input voltage range specification is shown on the post above. If you are powering the device with VSP=+15V and VSN=-15V, the INP and INN absolute voltage must not exceed the condition:

    (VSN)+2.5V < INP < (VSP)-2.5V or equivalently -12.5 < INP < +12.5V

    In this case, since you are connecting INP to +15V and have set the supply VSP = +15V, the PGA281 is outside the allowed input voltage range, and the error flag turns on.

    Thank you and Regards,

    Luis