CDB5378 Datasheet, PDF (16/72 Pages) Cirrus Logic – Single-channel Seismic Evaluation System

CDB5378
Land Common Mode Filter Specification
Common Mode Capacitance
Common Mode Resistance
Common Mode -3 dB Corner @ 6 dB/octave
Land Differential Filter Specification
Differential Capacitance
Differential Resistance
Differential -3 dB Corner @ 6 dB/octave
Marine Common Mode Filter Specification
Hydrophone Group Capacitance
Common Mode Resistance
-3 dB Corner @ 6 dB/octave
Marine Differential Filter Specification
Differential Capacitance
Differential Resistance
-3 dB Corner @ 6 dB/octave
Value
10 nF + 10%
200 Ω
80 kHz + 10%
Value
10 nF + 10%
200 Ω + 200 Ω = 400 Ω
40 kHz + 10%
Value
128 nF + 10%
825 kΩ || 825 kΩ = 412 kΩ
3 Hz + 10%
Value
10 nF + 10%
200 Ω + 200 Ω = 400 Ω
40 kHz + 10%
2.2.1.6 Common Mode Bias
Differential analog signals into the CS3301/02 amplifiers are required to be biased to the center of the
power supply voltage range, which for bipolar supplies is near ground potential. This common mode bias
voltage is created by buffering the voltage reference, which is nominally +2.5 V relative to the VA- power
supply.
By default, CDB5378 uses the CS3301 differential geophone amplifier and so the common mode bias re-
sistors on the INA inputs are set for land applications. Marine applications using the CS3302 amplifier will
need to modify the default common mode bias resistors.
Resistors to create the common mode bias are normally selected based on the sensor impedance and
may need to be modified from the CDB5378 defaults depending on the sensor used. Refer to the recom-
mended operating bias conditions for the selected sensor, which are available from the sensor manufac-
turer.
Specification
Geophone Sensor Bias Resistance
Hydrophone Sensor Bias Resistance
Value
20 kΩ || 20 kΩ = 10 kΩ
18 MΩ || 18 MΩ = 9 MΩ
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DS639DB3