Cirrus Logic CDB5374 - Manual (Page 14)

CDB5374
14 DS862DB1
2.2 Analog Hardware
2.2.1 Analog Inputs
2.2.1.1 External Inputs - INA, INB, BNC
External signals into CDB5374 are typically from piezoelectric hydrophones, which are high-impedance
sensors optimized to measure pressure in marine applications.
External signals connect to CDB5374 through screw terminals on the left side of the PCB. For each chan-
nel (CH1, CH2, CH3, CH4), these screw terminals make connections to two external differential inputs,
INA and INB. In addition, GND and GUARD connections are provided for connecting sensor cable shields,
if present.
2.2.1.2 GUARD Output, GND Connection
The CS5374 hydrophone amplifier provides a GUARD signal output designed to actively drive the cable
shield of a high impedance sensor with the common mode voltage of the sensor differential signal. This
GUARD output on the cable shield minimizes leakage by minimizing the voltage differential between the
sensor signal and the cable shield.
The GUARD signal is output to screw terminals on the left side of the PCB and a separate GND connec-
tion screw terminal for each channel is also provided if a ground connection to the sensor cable shield is
preferred.
2.2.1.3 Internal Inputs - DAC_OUT, DAC_BUF
The CS4373A test DAC has two high-performance differential test outputs, a precision output
(DAC_OUT) and a buffered output (DAC_BUF). These test outputs can be connected to the INA or INB
inputs of any channel through the input selection jumpers.
By default, CDB5374 is populated with passive RC filter components on the INA inputs, and no filter com-
ponents on the INB inputs (though the component footprints are present on the INB inputs). Because the
CS4373A precision output will not tolerate significant loading, on CDB5374 the DAC_OUT signal should
only jumper to the INB inputs. The CS4373A buffered outputs are less sensitive to the RC filter load and
DAC_BUF can be jumper-ed to either the INA or INB inputs.
Signal Input Screw Terminal
CH1 INA J32
CH1 INB J41
CH2 INA J232
CH2 INB J241
CH3 INA J332
CH3 INB J341
CH4 INA J432
CH4 INB J441
Table 7. Screw Terminal Input Connectors