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PGA281: PGA281 alternative

jeno.zhang
Genius 3635 points

Part Number: PGA281
Other Parts Discussed in Thread: PGA280, PGA206, INA851

HI TI，

Since PGA281 is out of stock now, it is necessary to find an alternative.

Is there any recommended circuit scheme using operational amplifier or instrument amplifier?

  • 0
    TI__Guru 55466 points

    Hello, 

    We do not have a direct pin-to-pin replacement for the PGA281.  The closest device would be the PGA280 which is currently out of stock.  Unfortunately, we do not offer a reference design to replace  PGA281 since this would be a very complex, expensive discrete circuit.  The PGA281 is a highly integrated device offering low offset, low gain error and ultra low drift offering 8 binary gains ranging for 128-V/V to attenuation of 1/8-V/V.  

    One possibility is to use an instrumentation amplifier and switch a couple of different RG gain resistors using low on-resistance, low capacitance photo-mos relays or mechanical relays.   Keep in mind, the circuit will become expensive as you add more gain options. 

    There is also the PGA206 offering binary gains 1 to 8, that may fit your application depending on your common-mode voltage and gain requirements. If you require fully-differential output, you could follow the PGA206 with a fully-differential amplifier.

    What sensor or circuit are you measuring? What is the common-mode voltage range? what is the differential voltage?  What is the gain error target? Do you require a fully differential output? What gain and attenuations settings do you require? 

    Thank you and Regards,

    Luis

       

  • 0 in reply to Luis Chioye
    TI__Guru 55466 points

    Hello,   

    There are several possibilities, if you require differential output, below find a couple possibilities:

    1) One possible solution requires to drive a fully-differential ADC, one possibility is to use the INA851, a number of analog switches, 4- precision amplifiers and a number of high precision, low-drift resistors or matched resistor networks. The number of resistors and channels on each switch depends on the number of gains required.  The accuracy of the solution will be directly related to the drift matching of the resistor network. Below is a block diagram.   

    2) Another simpler solution is using the PGA206 followed with a Fully-differential amplifier to perform single-ended to differential conversion; this may meet the requirement depending on your gain and/or common-mode voltage needs,

    If you require more detailed answer, please answer the questions:

    A) A similar E2E query was submitted yesterday in the link below.  Kindly clarify if this is this the same duplicate case/request, or if this is a separate/unrelated case.  See below:

    PGA281: Replace PGA281

    B) If this is not the same case, What sensor or circuit are you measuring? What is the common-mode voltage range? what is the differential voltage?  What is the gain error/accuracy error target and resolution? Do you require a fully differential output? What gain and attenuations settings do you require? 

    Thank you and Regards,

    Luis