18

DS691F1

CS4350

4. APPLICATIONS

4.1

Sample Rate Range and Oversampling Mode Detect

The device operates in one of three oversampling modes based on the input sample rate. In Control Port

Mode, the allowed sample rate range in each mode will depend on how the FM[1:0] bits are configured. In

Stand-Alone Mode, the sample rate range will be according to Table 1.

4.1.1

Sample Rate Auto-Detect

The Auto-Detect feature is enabled by default. In this state, the CS4350 will auto-detect the correct mode

when the input sample rate (Fs), defined by the LRCK frequency, falls within one of the ranges shown in

Table 1. Sample rates outside the specified range for each mode are not supported when Auto-Detect is

enabled.

In Control Port Mode, the Auto-Detect feature can be disabled by the Functional Mode (FM[1:0]) bits in

the control port register 02h. In this state, the CS4350 will not auto-detect the correct mode based on the

input sample rate (Fs). The operational mode must then be set manually according to one of the ranges

referred to in Section 8.2.3. Sample rates outside the specified range for each mode are not supported.

In Stand-Alone Mode it is not possible to disable auto-detect of sample rates.

4.2

System Clocking

The device requires external generation of the left/right (LRCK) and serial (SCLK) clocks. The left/right clock

frequency is equal to the input sample rate (Fs).

Refer to Section 4.3 for the required SCLK-to-LRCK timing associated with the selected digital interface for-

mat, and “Switching Specifications - Serial Audio Interface” on page 13 for the maximum allowed clock fre-

quencies.

4.2.1

Recovered Master Clock (RMCK)

The CS4350 generates a high-frequency master clock (RMCK) which it derives from the LRCK input,

available on the RMCK pin. In Stand-Alone Mode, the frequency of RMCK is equal to 256 x LRCK in Sin-

gle-Speed and Double-Speed Mode; and 128 x LRCK in Quad-Speed Mode. In Control-Port Mode, the

frequency of the RMCK signal can be selected through register 08h (see Section 8.7 on page 34 for more

details).

Input Sample Rate (Fs)

Mode

30 kHz - 54 kHz

Single-Speed Mode

60 kHz - 108 kHz

Double-Speed Mode

120 kHz - 216 kHz

Quad-Speed Mode

Table 1. CS4350 Auto-Detect