Cirrus Logic CDB5571 - Manual (Page 7)

CDB5571
DS768DB4 7
The analog inputs are designed for connections to single-ended input signals referenced to ground. The
usable input voltage range is -2.048 V to +2.048 V. The theoretical input frequency range of the CS5571
is from DC to the Nyquist frequency of 50 kHz. The analog input buffer amplifiers are configured for a cut-
off frequency of 16.8 kHz to band-limit noise into the ADC. Changing the cutoff frequency will change the
noise bandwidth accordingly.
3.3.2 Multiplexer
Analog input channel selection is controlled through the multiplexer. The multiplexer is configured with a
pull-down resistor on the MUX control line to enable input channel labeled "INPUT A" by default. To select
channel B, apply 3.3 V to the multiplexer input control line (MUX).
Signal levels for controlling the multiplexer that selects between analog input channels A and B is shown
in Table 3.
During multiplexing, the maximum sample rate for each channel is half that of the ADC’s maximum sam-
ple rate. Additionally, the Nyquist frequency for each channel is half of the ADC’s Nyquist frequency.
3.3.3 ADC Reset
The CS5571 ADC makes use of an externally generated power-on reset. Therefore, after power is ap-
plied to the ADC, the reset pin must be driven low then released. Pressing the Reset button generates a
reset cycle. A reset cycle can be generated at any time during ADC operation. The ADC RST pin (active
low) is held inactive through a pull-up resistor.
3.3.4 Voltage Reference
The voltage reference IC provided generates a 4.096 V precision reference.
3.3.5 ADC Reference Frequency
The reference frequency for the CS5571 ADC is provided by a 16.000 MHz oscillator.
Table 3. Analog Input Channel Selection
Multiplexer
Control Input (MUX)
Input Channel
Enabled
0 V A
3.3 V B