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ADS1284: Doubt about voltages

Michele Bertoni1
Intellectual 340 points
Part Number: ADS1284

Hi to all users!
I'm planning to design ADC for seismic purposes.
Taking a look to ADS1284 datasheet I can see I can power ADS1284 with dual supply +/-2.5V.

Datasheet:

AVSS = from -2.6  to 0.0 [Volt]
AVDD = from AVSS+4.75 to AVSS+5.25 [Volt]
AINP or AINN = from AVSS+ 0.7 to AVDD– 1.25 [Volt]

If I choose AVSS = -2.5V, AVDD = +2.5V, I get AINP or AINN from -1.8 to 1.0 Volt, is this correct?

In this case I have these two options:
1) single ended, bipolar input signal
 AINN to AVSS, AINP = from -1.0 to +1.0 Volt (so Vin = AINP-AINN = from -1.0 to +1.0 = 2Vpeak-to-peak)

2) differential bipolar input signal
AINN and AINP = from -1.0 to +1.0 Volt (so Vin = AINP-AINN = from -2.0 to +2.0 = 4Vpeak-to-peak)

Working with dual power supply I supposed negative range mirrired to positive range to cover full range....
Thanks.

  • 0
    TI__Mastermind 40950 points

    Hello Michele,

    The maximum input voltage for AINP and AINN will be +1.25V with AVDD=+2.5V.

    AINP or AINN = from AVSS+ 0.7 to AVDD– 1.25 [Volt]

    With a PGA gain of 1, and Vref=5V, this allows a full scale input range of +/-2.5V differential (AINN=-/+1.25V and AINP=+/-1.25V) when operating from +/-2.5v supplies.

    Singled ended bipolar will support up to +/-1.25V, or 2.5Vpeak-to-peak and differential bipolar will support up to +/-2.5V, or 5Vpeak-to-peak.

    Regards,
    Keith Nicholas
    Precision ADC Applications