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Original question:

ADS1675: ADS1675 DVDD To GND

ADS1675: ADS1675

Blanche Duan
Prodigy 250 points
Part Number: ADS1675

Hi,

There are two question about ADS1675: 

1. PIN 40 (OTRA), Is it an input pin or an output pin？

2、 What is the analog input range of AD1675？ 

According to the manual, the analog input range is ±VREF=±3V, and the common mode input is ±2.5V. Then the range of ADC input will be - 0.5V~5.5V, while the voltage of ADC is only 5V. Does the range of analog input voltage not exceed the power supply range of ADC? Is it unreasonable?

  • 0
    TI__Mastermind 41200 points
    Hi Blanche,

    For question 1, both the OTRA and OTRD pins are digital outputs. The Terminal Functions table is incorrect.

    For question 2, the inputs AINP and AINN should not exceed AVDD or go below ground (0V). These inputs should only have positive voltages applied to them. Since the ADS1675 uses differential inputs, the full scale DIFFERENTIAL input range is +/-VREF.

    As an example with VREF=3V and the average input voltage (common mode input voltage) = 2.5V.

    AINP=+4V, AINN=+1V, (AINP-AINN)=+3V or +VREF, the conversion result will be 0x7FFFFFh, or positive full scale equal to +VREF.
    AINP=+1V, AINN=+4V, (AINP-AINN)=-3V or -VREF, the conversion result will be 0x800000h, or negative full scale equal to -VREF.

    In both of the above cases, the average, or common-mode, voltage will equal 2.5V. You could drive the inputs at a different common mode voltages from 1.5V to 3.5V, but the guaranteed specifications are valid for 2.5V only.

    Regards,
    Keith N.
    Precision ADC Applications
  • 0 in reply to Keith Nicholas
    Prodigy 250 points

    Hi Keith ，

    got it,  thanks for your support!