
[AK4345] 
OPERATION OVERVIEW 
■
 System Clock 
The external clocks, which are required to operate the AK4345, are MCLK, BICK and LRCK. 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. The MCLK frequency is detected from the relation between MCLK and LRCK 
automatically. The Half speed, the Normal speed and the Double speed mode are selected with the DFS1-0 bits (Table 1). 
The sampling speed mode is set depending on the MCLK frequency automatically for Auto mode (DFS1 bit = DFS0 bit = 
“1”) (Table 2). 
The AK4345 is automatically placed in the reset mode when MCLK stops in the normal operation mode (PDN pin = “H”), 
and the analog output becomes the VCOM voltage. After MCLK is input again, the AK4345 is powered up. After exiting 
reset by PDN pin at power-up etc., the AK4345 is in the reset mode until MCLK and LRCK are input. 
Mode 
DFS1 
DFS0 
Normal Speed 
0 
0 
Double Speed 
0 
1 
Half Speed 
1 
0 
Auto 
1 
1 
Table 1. System Clock Example 
MCLK Frequency 
Sampling Speed Mode 
512/768fs 
Normal Speed 
128/192/256/384fs 
Double Speed 
1024/1536fs 
Half Speed 
Table 2. Auto Mode 
■
 Audio Interface Format 
The Data is shifted in via the SDTI pin using BICK and LRCK inputs. The DIF1-0 bits as shown in Table 3 can select four 
serial data modes. In all modes the serial data is MSB-first, 2’s compliment format and is latched on the rising edge of 
BICK. Mode 3 can be used for 16bit I
2
S Compatible format by zeroing the unused LSBs at BICK 
≥
 48fs or BICK = 32fs. 
Mode 
DIF1 
DIF0 
0 
0 
0 
16bit, LSB justified 
1 
0 
1 
24bit, LSB justified 
2 
1 
0 
24bit, MSB justified 
3 
1 
1 
16/24bit, I
2
S Compatible
Table 3. Audio Interface Format 
fs 
MCLK Frequency 
256/384/512/768fs 
128/192/256/384fs 
512/768/1024/1536fs 
Table 2
8 
~
 48kHz 
48 
~
 96kHz 
8 
~
 24kHz 
8 
~
 96kHz 
Fs 
8 
~
 48kHz 
48 
~
 96kHz 
8 
~
 24kHz 
SDTI Format 
BICK 
≥
 32fs 
≥
 48fs 
≥
 48fs 
Figure 
Figure 10
Figure 11
Figure 12
Figure 13
≥
 48fs or 32fs 
MS0635-E-00 
2007/06 
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