CS4364 Datasheet, PDF (24/50 Pages) Cirrus Logic – 103 dB, 192 kHz 6-Channel D/A Converter

3.3.3
CS4364
TDM
The TDM serial audio interface format operates in single, double, or quad-speed mode and will slave to
SCLK at 256 Fs. Data is received most significant bit first on the first SCLK after an LRCK transition and
is valid on the rising edge of SCLK. LRCK identifies the start of a new frame and is equal to the sample
rate, Fs. LRCK is sampled as valid on the rising SCLK edge preceding the most significant bit of the first
data sample and must be held valid for one SCLK period. Each time slot is 32 bits wide, with the valid data
sample left justified within the time slot with the remaining bits being zero padded.
LRCK
SCLK
SDIN1
256 clks
MSB
LSB MSB
LSB MSB
LSB
DAC_A1
DAC_A2
DAC_A3
32 clks
32 clks
32 clks
32 clks
MSB
LSB MSB
LSB MSB
LSB
DAC_B1
DAC_B2
DAC_B3
32 clks
32 clks
32 clks
32 clks
Data
MSB
LSB
zero
Figure 17. Format 12 - TDM Mode
3.4 Oversampling Modes
The CS4364 operates in one of three oversampling modes based on the input sample rate. Mode selection
is determined by the M4, M3 and M2 pins in hardware mode or the FM bits in software mode. Single-Speed
mode supports input sample rates up to 50 kHz and uses a 128x oversampling ratio. Double-Speed mode
supports input sample rates up to 100 kHz and uses an oversampling ratio of 64x. Quad-speed mode sup-
ports input sample rates up to 200 kHz and uses an oversampling ratio of 32x.
The auto-speed mode detect feature allows for the automatic selection of speed mode based off of the in-
coming sample rate. This allows the CS4364 to accept a wide range of sample rates with no external inter-
vention necessary. The auto-speed mode detect feature is available in both hardware and software mode.
3.5 Interpolation Filter
To accommodate the increasingly complex requirements of digital audio systems, the CS4364 incorporates
selectable interpolation filters for each mode of operation. A “fast” and a “slow” roll-off filter is available in
each of Single, Double, and Quad-Speed modes. These filters have been designed to accommodate a va-
riety of musical tastes and styles. The FILT_SEL bit is used to select which filter is used (see the “Parameter
Definitions” on page 47 for more details).
When in hardware mode, only the “fast” roll-off filter is available.
Filter specifications can be found in Section 2, and filter response plots can be found in Figures 26 to 49.
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DS619A1