[AK4421]

MS0945-E-01

2008/08

- 9 -

OPERATION OVERVIEW

The external clocks required to operate the AK4421 are MCLK, LRCK, and BICK. The master clock (MCLK) should be

synchronized with LRCK, but the phase is not critical. The MCLK is used to operate the digital interpolation filter and the

delta-sigma modulator. Sampling speed and MCLK frequency are detected automatically, and then the internal master

clock is set to the appropriate frequency (Table 1).

The AK4421 is automatically placed in power saving mode when MCLK and LRCK stop during normal operation mode,

and the analog output goes to 0V(typ). When MCLK and LRCK are input again, the AK4421 is powered up. After exiting

reset following power-up, the AK4421 is not fully operational until MCLK and LRCK are input.

LRCK

MCLK (MHz)

fs

128fs

192fs

256fs

384fs

512fs

768fs

1152fs

Sampling

Speed

32.0kHz

-

-

-

-

16.3840

24.5760

36.8640

44.1kHz

-

-

-

-

22.5792

33.8688

-

48.0kHz

-

-

-

-

24.5760

36.8640

-

Normal

88.2kHz

-

-

22.5792

33.8688

-

-

-

96.0kHz

-

-

24.5760

36.8640

-

-

-

Double

176.4kHz

22.5792

33.8688

-

-

-

-

-

192.0kHz

24.5760

36.8640

-

-

-

-

-

Quad

Table 1. System Clock Example

When MCLK= 256fs/384fs, the Auto Setting Mode supports sampling rate of 32kHz~96kHz (Table 1). But, when the

sampling rate is 32kHz~48kHz, DR and S/N will degrade by approximately 3dB as compared to when MCLK=

512fs/768fs (Table 2).

MCLK

DR,S/N

256fs/384fs

99dB

512fs/768fs

102dB

Table 2. Relationship between MCLK frequency and DR, S/N (fs= 44.1kHz)

The audio data is shifted in via the SDTI pin using the BICK and LRCK inputs. The DIF pin can select between two serial

data modes as shown in Table 3. In all modes the serial data is MSB-first, two’s complement format and it is latched on

the rising edge of BICK. In one cycle of LRCK, eight “H” pulses or more must not be input to the DIF pin.

Mode

DIF

SDTI Format

BICK

Figure

0

L

24bit MSB justified

≥48fs

Figure 3

1

H

≥48fs

Figure 4

Table 3. Audio Data Formats