CDB5374 Cirrus Logic Inc, CDB5374 Datasheet - Page 15

• Manufacturer Part Number: CDB5374
• Description: Audio Modules & Development Tools 2-Ch DS Modulator & Hydrophone Demo Brd
• Manufacturer: Cirrus Logic Inc

Specifications of CDB5374

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

2.2.1.4
Sensor inputs must have circuitry to protect the analog electronics from voltage spikes as hydrophones
can produce large voltage spikes if located near an air gun source.
Discrete switching diodes quickly clamp the analog inputs to the power supply rails when the input voltage
spikes. These diodes are reverse biased in normal operation and have low reverse bias leakage and ca-
pacitance characteristics to maintain high linearity on the analog inputs.
2.2.1.5
Following the diode clamps is an RC filter network that bandwidth limits the sensor inputs into the ampli-
fiers to “chop the tops off” residual voltage spikes not clamped by the discrete diodes. In addition, all Cirrus
Logic component ICs have built in ESD protection diodes guaranteed to 2000 V HBM / 200 V MM (JEDEC
standard). The small physical size of these ESD diodes restricts their current capacity to 10 mA.
For marine applications that use the CS3302A amplifier, the inherent capacitance of the piezoelectric sen-
sor is combined with large resistors to create an analog high-pass RC filter to eliminate the low-frequency
components of ocean noise.
2.2.1.6
Differential analog signals into the CS3301A/02A 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.
Resistors to create the common mode bias are selected based on the sensor impedance and may need
to be modified from the CDB5374 defaults depending on the sensor to be used. Refer to the recommend-
ed operating bias conditions for the selected sensor, which are available from the sensor manufacturer.
DS862DB1
Marine Differential Filter Specification
Hydrophone Group Capacitance
Differential Resistance
-3 dB Corner @ 6 dB/octave
Specification
Dual Series Switching Diode - ON Semiconductor
Surface Mount Package Type
Non-Repetitive Peak Forward Current (1 µs, 1 ms, 1 s)
Reverse Bias Leakage (25 C to 85 C)
Reverse Bias Capacitance (0 V to 5 V)
Specification
Hydrophone Sensor Bias Resistance
Input Protection
Input RC Filters
Common Mode Bias
Value
128 nF + 10%
412 kΩ + 2 kΩ = 400 Ω
40 kHz + 10%
Value
18 MΩ || 18 MΩ = 9 MΩ
Value
BAV99LT1
SOT-23
2.0 A, 1.0 A, 500 mA
0.004 µA - 0.4 µA
1.5 pF - 0.54 pF
CDB5374
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