System Clock

(SCK)

"L"

"H"

0.3*DVDD

0.7*DVDD

PCM5100, PCM5101, PCM5102

www.ti.com

SLAS764B – MAY 2011 – REVISED SEPTEMBER 2012

System Clock Input

The PCM510x requires a system clock to operate the digital interpolation filters and advanced segment DAC

modulators. The system clock is applied at the SCK input (pin 12) and supports up to 50MHz. The PCM510x

system-clock detection circuit automatically senses the system-clock frequency. Common audio sampling

frequencies of 8kHz, 16kHz, 32kHz - 44.1kHz - 48kHz, 88.2kHz - 96kHz, 176.4kHz -192kHz, and 384kHz with

±4% tolerance are supported. The sampling frequency detector sets the clock for the digital filter, Delta Sigma

Modulator (DSM) and the Negative Charge Pump (NCP) automatically. Table 3 shows examples of system clock

frequencies for common audio sampling rates.

SCK rates that are not common to standard audio clocks, between 1MHz and 50MHz, are only supported in

software mode, available only in the PCM512x and PCM514x devices, by configuring various PLL and clock-

divider registers. Software mode allows the device to become a clock master and drive the host serial port with

LRCK and BCK, from a non-audio related clock; for example, using 12MHz to generate 44.1kHz (LRCK) and

2.8224MHz (BCK).

Figure 12 shows the timing requirements for the system clock input. For optimal performance, it is important to

use a clock source with low phase jitter and noise.

Table 3. System Master Clock Inputs for Audio Related Clocks

Sampling

Frequency

8 kHz

2.0480

3.0720

4.0960

6.1440

8.1920

9.2160

12.2880

16.3840

24.5760

16 kHz

4.0960

6.1440

8.1920

12.2880

16.3840

18.4320

24.5760

36.8640

49.1520

32 kHz

8.1920

12.2880

16.3840

24.5760

32.7680

36.8640

49.1520

44.1 kHz

11.2896

16.9344

22.5792

33.8688

45.1584

48 kHz

12.2880

18.4320

24.5760

36.8640

49.1520

88.2 kHz

16.9344

22.5792

33.8688

45.1584

96 kHz

18.4320

24.5760

36.8640

49.1520

176.4 kHz

22.5792

33.8688

45.1584

192 kHz

24.5760

36.8640

49.1520

384 kHz

24.5760

49.1520

(1)

This system clock rate is not supported for the given sampling frequency.

(2)

This system clock rate is supported by PLL mode.

Figure 12. Timing Requirements for SCK Input

Table 4. Timing Requirements for SCK Input

Parameters

Min

Max

Unit

System clock pulse cycle time

20

1000

ns

System clock pulse width, High

9

ns

System clock pulse width, Low

9

ns

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