Cirrus-logic CDB5374 Manual de usuario descargar pdf (Pagina 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

1 2 ... 9 10 11 12 13 14 15 16 17 18 19 ... 77 78

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Cirrus-logic CDB5374 Manual de usuario Pagina 14