CS5397 datasheet(12/40 Pages) CIRRUS

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CS5396 CS5397

DS229PP2

GENERAL DESCRIPTION

The CS5396/97 is a 24-bit, stereo A/D converter

designed for stereo digital audio applications. The

analog input channels are simultaneously sampled

by separate, patented, 7th-order tri-level delta-sig-

ma modulators at either 128 or 64 times the output

sample rate (64

× Fs or 128× Fs) of the device. The

resulting serial bit streams are digitally filtered,

yielding pairs of 24-bit values at output sample

rates (Fs) of up to 100 kHz. This technique yields

nearly ideal conversion performance independent

of input frequency and amplitude. The converter

does not require difficult-to-design or expensive

anti-alias filters, and it does not require external

sample-and-hold amplifiers or voltage references.

Only normal power supply decoupling compo-

nents, voltage reference bypass capacitors and a

single resistor and capacitor on each input for anti-

aliasing are required, as shown in Figure 1. An on-

chip voltage reference provides for a differential

input signal range of 4.0 Vpp. The device also con-

tains a high pass filter, implemented digitally after

the decimation filter, to completely eliminate any

internal offsets in the converter or any offsets

present at the input circuitry to the device. Output

data is available in serial form, coded as 2’s com-

plement 24-bit numbers. For more information on

delta-sigma modulation techniques see the refer-

ences at the end of this data sheet.

Stand-Alone vs. Control Port Mode

The CS5396/97 can operate in either Stand-Alone

or Control Port Mode. The functionality of pins 17,

18 and 19 is established upon entering either the

Stand-Alone or Control Port mode, as described in

the Pin Description section.

The Control Port Mode requires a micro-controller

and allows access to many additional features,

which include:

•

128

× Oversampling Mode

•

Reduction of 24-bit data to 20, 18 or 16-bit data

with psychoacoustically optimized dither

•

Programmability of psychoacoustic filter coef-

ficients

•

Peak Input Signal Level Monitor with either

High Resolution or Bar Graph mode selection

•

Signal inversion

•

High pass filter defeat

•

Mute

•

Access to the digital filter to allow the input of

external digital audio data to produce a two-to-

one decimated output and/or psychoacoustic bit

reduction.

STAND-ALONE MODE

Master Clock - Stand-Alone Mode

The master clock is the clock source for the delta-

sigma modulator sampling (MCLKA) and digital

filters (MCLKD). The required MCLKA/D fre-

quency is determined by the desired Fs and must be

256

× Fs. Table 1 shows some common master

clock frequencies.

Table 1. Common Clock Frequencies for Stand-Alone

Mode

Serial Data Interface - Stand-Alone Mode

The CS5396/97 supports two serial data formats

which are selected via the digital format select pin,

DFS. The digital output format determines the rela-

tionship between the serial data, left/right clock and

serial clock. Figures 2 and 3 detail the interface for-

LRCK

(kHz)

MCLKA/D

(MHz)

SCLK

(MHz)

8.192

2.048

44.1

11.2896

2.822

12.288

3.072

16.384

4.096

88.2

22.5792

5.6448

24.576

6.144

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