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PGA281: Operation of PGA281 for Min Input voltage supply

Rajesh Kaliyaperumal
Intellectual 930 points
Part Number: PGA281
Other Parts Discussed in Thread: PGA280, PGA112, PGA116

Hi ,

I am using PGA281 with input stage supply of 10 volts Nominal (VSP=10 V and VSN=0V). But in my system, the supply voltage may vary upto 9.5 Volts ( 10 +/- 5% worst case).

In the least case of 9.5 Volts supply, How will be performance of PGA281 ?? We want to confirm as you have mentioned  in the datasheet that min. supply voltage of 10 V for PGA281 (Shown below)

Or could you suggest us the equivalent part to PGA281 with the following features:

1) Operating input supply voltage of 7 to 18 V

2) Gain is programmable by GPIOs from microcontroller.

3) Output type is differential similar to PGA281

Appreciate your help at the earliest. Thanks in Advance!

Regards,

Rajesh K

  • 0
    TI__Guru 55466 points

    HI Rajesh,

    If the nominal supply used is VSP=10V and VSN=0V, with 5% variation, with a minimum supply of 9.5V, the device will function.

    However, keep in mind the input voltage range is delimited by the VSP/VSN supplies, therefore the inputs must always be within the range (VSN) +2.5V and (VSP) -2.5V at all times.  Unfortunately, there are no other equivalent devices with the same GPIO functionality and gain for a lower supply voltage range.

    Best Regards,

    Luis 

  • 0 in reply to Luis Chioye
    Intellectual 930 points

    Hi Luis,

    Thanks for the confirmation on working of the PGA281 at minimum voltage of 9.5 Volts. Our Input ranges will be around 5 Volts hence it will be an issue.

    Regarding the alternate for PGA281: Even I2C Interface amplifiers (for programming gain) would be fine for us. Meanwhile I will also try to find the alternate parts.Will get back to you if I find one.

    Also I have query that " what is the best way to give excitation voltage to the Full bridge Wheatstone type of sensor ?? Either from LDO or From DC-DC Buck Boost converters which is better ??

    Because we are concerned about the Ripple Voltage at the output of DC- DC converter would inject noise in the measurements of parameters from sensor.

    Appreciate your help at the earliest!!

    Regards,

    Rajesh K

  • 0 in reply to Rajesh Kaliyaperumal
    TI__Guru 55466 points
    HI Rajesh,

    When performing precision measurements, Wheatstone bridges require the use of a low noise, low drift, and stable voltage excitation; since the output of the sensor is proportional to both the change in resistance in the sensor and the excitation voltage. Precision voltage references are often used as voltage excitations sources for Wheatstone bridges. As you have mention, the DC-DC converter ripple and drift may degrade the noise performance and repeatability of the measurement.

    Thank you and Regards,

    Luis
  • 0 in reply to Luis Chioye
    TI__Guru 55466 points
    HI Rajesh,

    The PGA280 and PGA281 are the only differential input and differential output precision programmable amplifier; but they require the minimum 10V nominal supply.

    We offer the PGA112 and PGA116 that offer binary gains and will work at a lower supply voltage, but these are single-ended input and single-ended output, so they are not equivalent.

    Thank you and Regards,

    Luis Chioye
  • 0 in reply to Luis Chioye
    Intellectual 930 points
    Hi Luis Chioye,

    Thanks for the clarification.

    Regards,

    Rajesh