Cirrus Logic CRD5378 - Manual (Page 18)

CRD5378
18 DS639RD2
2.2.4 Delta-Sigma Test DAC
The CS5373A test DAC creates differential analog signals for system tests. Multiple test modes are avail-
able and their use is described in the CS5373A data sheet.
2.2.4.1 Precision Output - DAC_OUT
The CS5373A test DAC has a precision output (DAC_OUT) that is routed directly to the amplifier INB in-
puts. The input impedance of the CS3301A/02A INB amplifier inputs are high enough that the precision
output can be directly connected to the INB inputs.
2.2.4.2 Buffered Output - DAC_BUF
The CS5373A test DAC has a buffered output (DAC_BUF) that is routed to the amplifier INA inputs. This
output is less sensitive to loading than the precision outputs, and can drive a sensor attached to the am-
plifier INA inputs provided the sensor meets the impedance requirements specified in the CS5373A data
sheet.
2.2.5 Voltage Reference
A voltage reference on CRD5378 creates a precision voltage from the regulated analog supplies for the
modulator and test DAC VREF inputs. Because the voltage reference output is generated relative to the
negative analog power supply, VREF+ is near GND potential for bipolar power supplies.
Analog Signals Description
OUT Precision differential analog output
BUF Buffered differential analog output
CAP Capacitor connection for internal anti-alias filter
VREF Voltage reference analog inputs
Digital Signals
Description
TDATA Delta-sigma test data input
MCLK Clock input
SYNC Synchronization input
MODE[0..2] Test mode selection
ATT[0..2] Attenuation range selection
Specification Value
Precision Reference - Linear Tech
LT1019AIS8-2.5
Surface Mount Package Type SO-8
Output Voltage Tolerance +/- 0.05%
Temperature Drift 10 ppm / degC
Quiescent Current 0.65 mA
Output Voltage Noise, 10 Hz - 1 kHz 4 ppm
RMS
Ripple Rejection, 10 Hz - 200 Hz > 100 dB