Cirrus-logic CDB5560 User Manual download pdf (Page 7)

CDB5560

DS713DB4 7

For detailed information on the LMP7732 precision industrial op-amps, please visit National Semiconduc-

tor’s website at www.national.com

The analog inputs are designed for connections to differential input signals. The usable input voltage

range is -4.096 V to +4.096 V. The theoretical input frequency range of the CS5560

is from DC to the

Nyquist frequency of 25 kHz. The analog input buffer amplifiers are configured for a cutoff 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 CS5560 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 CS5560 ADC is provided by a 16.000 MHz oscillator.

Table 3. Analog Input Channel Selection

Multiplexer

Control Input (MUX)

Input Channel

Enabled

0V A

3.3 V B

1 2 3 4 5 6 7 8 9 10 11 12 ... 25 26

No comments

Cirrus-logic CDB5560 User Manual Page 7