ADS1283IRHFR.B datasheet(53/67 Pages) TI2

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ADS1283

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SBAS565C – JANUARY 2014 – REVISED AUGUST 2019

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Typical Applications (continued)

The geophone input signal is filtered by both a differential filter (components C4 and R1 to R4) and by common-

mode filters (components C2, C3 and R1, R2). The differential filter removes high-frequency normal-mode

components from the input signal. The common-mode filters remove high-frequency components that are

common to both input leads. The input filters are not required for all applications; check the system requirements

for each application.

Resistors R5 and R6 bias the signal input to the midsupply point (ground). For single-supply operation, set the

bias to a low impedance midsupply point (AVDD / 2 = 2.5 V).

Optional diode clamps protect the ADS1283 inputs from high-level voltage transients and overloads. The diodes

provide additional protection if possible high-level input transients and surges exceed the ADC internal ESD

diode rating.

The REF5050 5-V reference provides the reference to the ADC. An optional filter network (R7 and C5) reduces

the in-band reference noise for improved dynamic performance. However, the RC filter network increases the

filter settling-time (from seconds to possibly minutes) depending on the dielectric absorption properties of

capacitor C5. Capacitor C7 is mandatory and provides high-frequency bypassing of the reference inputs; place C7

as close as possible to the ADS1283 pins. Resistor R7 (1 kΩ) results in a 1% systematic gain error. Multiple

ADCs can share a single reference, but if shared, use independent reference filters for each ADC.

As an alternative, the REF5045 (4.5 V) reference can be used. The REF5045 reference has the advantage of

operating directly from the 5-V (total) power supply; however, the 4.5-V reference reduces signal range by 10%

and results in a 1-dB loss of SNR.

Capacitor C6 (10 nF) filters the PGA output glitches caused by sampling of the modulator. This capacitor also

forms an antialias filter with a low-pass cutoff frequency of 26 kHz.

ADS1283IRHFR.B Datasheet(PDF) 53 Page - Texas Instruments