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ADS8588H: need PGA for ADS8588H

Part Number: ADS8588H
Other Parts Discussed in Thread: INA188, TMUX6219, OPA2197, TMUX6236

Dear TI,

We need a programmable Gain amplifier which should have gains of 10 and 50,

input to ADC AD8588H is being fed from current transformer, and we want PGA to be inserted in between ADC and Current Transformer,

Input voltage to PGA will be 50Hz AC signal of amplitude +/-1V maximum, output voltage maximum will be +/-10V from PGA and being fed to ADS8588H,

may you please suggest any suitable part

  • Hi I,

    I'm not an expert in PGAs so I'll have to loop in another team. I think we'll be hard pressed to find +/-10V and G = 50, but I'll let the other experts help us out.

    Can you confirm that you need the gain switching to be dynamic and programmable or are you open to discreet solutions as well? We have other reference designs that use instrumentation amplifiers or discreet, check out this referenced design: High Accuracy Analog Front End Using 16-Bit SAR ADC with ±10V Measurement Range Reference Design -> 



  • Dear Cole Macias,

    Gain switching needs to be dynamic / software configurable(like toggling a gpio to select 10 or 50 gain or send command over SPI interface etc)

    open to discrete solutions as well

    yes i followed TIDA000834 for fixed gains , and now we need to change gain dynamically

  • HI I,

    What is the gain error target on the application? 

    A) One simple solution, depending on the gain error requirement in the application, is to use an instrumentation amplifier such as the INA188 with a 2:1 analog switch:

    • We can split the instrumentation amplifier RG gain resistor into 3 segments, and use an analog switch to short the middle resistor to increase gain.
    • If we use 3 series resistors for RG = 511Ω + 4.53kΩ + 511Ω = 5,552Ω, the INA188 gain is ~10.005V/V with the analog switch on the S2 position (OPEN)
    • A low resistance (RON=~2Ω typical) analog switch such as TMUX6219  supporting 36V supplies (or similar) can be used to short the 4.53kΩ middle resistor, to obtain RG = 511Ω + ~2.1Ω + 511Ω = 1,024Ω gain of approximately ~49.84V/V with the switch on S1 position (closed)s.
    • The gain error at G=50x, when the switch is closed is a function of the RG resistor tolerances, and the RON switch resistance variation.  The RON resistance variation is approximately ~3 Ohm across voltage, hence the gain error due to RON is roughly ~3/1024Ω*100%= ~0.3%.  We could also use multiple channel switches in parallel to reduce the RON resistance.  

    INA188 circuit:  INA188_TINA.TSC

    B) If you require very low gain error, and excellent linearity, another possibility is using the instrumentation amplifier followed by a dual op-amp programmable gain stage built with analog switches using Kelvin Sense connections. 

    • In this circuit, the INA188 is set a fixed gain of 5x
    • The second programmable gain amplifier stage uses a dual op-amp (OPA2197) and a 2-channel, 2:1 (TMUX6236).  This stage offer programmable gains of 2x and 10x.
    • This OPA2197+TMUX6236 circuit provides accurate Kelvin connection sensing the gain resistors for each gain. Since the input bias current of the buffer operational amplifier is minimal, less than ~10 pA, the voltage drop across the switch RON resistance is negligible.
    • This circuit will provide very low gain error, and excellent linearity.

    Let me know which approach is preferred in your application.

    Thank you and Kind Regards,


  • Dear Luis, we are evaluating the suggested solutions 

    thanks you very much for detailed explanation with diagrams, it helped lot to understand better, thanks

  • HI I,

    Glad to help,

    Thank you very much,

    Kind Regards,