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ADS1230: Input common mode voltage range @VDD=3V

Kuramochi Tadahiko
Guru 28715 points
Part Number: ADS1230

Hi,

Input common mode voltage range is specified "AGND+1.5V~VDD-1.5V".

If VDD=3V, this voltage range is nothing.

Could you show me the correct voltage range at VDD=3V?

Best Regards,

Kuramochi

  • 0
    TI__Guru** 112725 points
    Hi Kuramochi-san,

    The specification you are referring to is the common-mode input voltage range. At 3V VDD, the common-mode voltage is specified at 1.5V only and there is no range of common-mode voltages as can be used with larger supply voltages. The common-mode voltage of the sensor output is (AINP + AINN)/2 (or the average of the 2 absolute input voltages with respect to AGND).

    The absolute input range for the ADS1230 is the common-mode input voltage +/- (0.5Vref/GAIN). As the ADS1230 was designed primarily for making bridge measurements, such as a load cell) the common-mode from the bridge is 1/2 of the excitation supply. If the excitation supply is also used as the reference supply (making a ratiometric measurement) then there should be no issue.

    Best regards,
    Bob B
  • 0 in reply to Bob Benjamin
    Guru 28715 points
    Bob-san,

    Thank you for your information.

    How about the case of VDD=2.7V?
    Is common voltage range nothing?

    Best Regards,
    Kuramochi
  • 0 in reply to Kuramochi Tadahiko
    TI__Guru** 112725 points
    Hi Kuramochi-san,

    The 2.7V supply case is similar to the 3.0V supply. The amplifier will maintain linearity when the common-mode input is at 1/2 of the analog supply. If the common-mode deviates the output of the amplifier may try to drive to the rail which it cannot do. This will show up as a linearity error.

    It can be assumed that a safe operating region is when the common-mode is 1/2 of AVDD. With higher supplies, the common-mode can deviate safely within the range of AVDD-1.5V and AGND+1.5V.

    Best regards,
    Bob B