Cirrus Logic CRD5376 - Manual (Page 16)

CRD5376
16 DS612RD2
2.2.2 Differential Amplifiers
The CS3301A/02A amplifiers act as a low-noise gain stage for internal or external differential analog sig-
nals.
2.2.2.1 MCLK/2 Input vs. GUARD Output
By default, channels 1 and 2 of CRD5376 use the CS3301A geophone amplifier while channels 3 and 4
use the CS3302A hydrophone amplifier. The CS3301A amplifier is chopper stabilized and connects pin
13 to a clock source (MCLK/2) to run the chopper circuitry synchronous to the modulator analog sampling
clock. The CS3302A device is not chopper stabilized (with 1/f noise typically buried below the low-fre-
quency ocean noise) to achieve very high input impedance. To minimize leakage from high impedance
sensors connected to the CS3302A amplifier, pin 13 produces a GUARD signal output to actively drive a
sensor cable shield with the common mode voltage of the sensor signal.
Comparing the CS3301A and CS3302A amplifiers, the functionality of pin 13 (CLK input vs. GUARD out-
put) is the only external difference. CRD5376 can be converted to use any combination of CS3301A and
CS3302A amplifiers by replacing the amplifier device and properly installing the pin 13 jumpers. Only one
set of pin 13 jumpers should be installed per channel (either CS3301A or CS3302A), and the others re-
moved.
Common amplifier configurations for CRD5376 include 3x or 4x CS3301A amplifiers for land applications,
4x CS3302A amplifiers for marine streamer applications, and 3x CS3301A amplifiers plus 1x CS3302A
amplifier for seabed reservoir monitoring applications. Replacement amplifiers can be requested as sam-
ples from the local Cirrus Logic sales representative.
Analog Signals Description
INA Sensor analog input
INB Test DAC analog input
OUTR, OUTF Analog rough / fine outputs
GUARD CS3302A guard output (jumper selection)
Digital Signals
Description
MUX[0..1] Input mux selection
GAIN[0..2] Gain range selection
PWDN Power down mode enable
CLK CS3301A clock input (jumper selection)
Amplifier CS3301A CS3302A
CH1 U16 R128 + R84 R129
CH2 U2 R86 + R92 R87
CH3 U33 R95 + R132 R94
CH4 U3 R58 + R100 R59
Table 6. Amplifier Pin 13 Jumper Settings