AK7755EN_16 Datasheet, PDF (27/109 Pages) Asahi Kasei Microsystems – DSP with Mono ADC Stereo CODEC + Mic/Lineout Amp

[AK7755]
2-1. Master Mode (CKM mode 0, 1: Using XTI Input Clock)
fs: Sampling Frequency
CKM CKM XTI
Input Frequency Range
Use of Chrystal
mode [2:0] _{fs:48kHz series fs:44.1kHz series} (MHz)
Oscillator
0
000 12.288MHz 11.2896MHz
11.0 to 12.4
Available
1
001 18.432MHz 16.9344MHz
16.7 to 18.6
Available
Input system clock to the XTI pin by setting BITFS[1:0] bits. The internal counter which is synchronized to
XTI generates LRCK(1fs) and BICK(64fs, 48fs, 32fs, 256fs). BICK frequency can be selected by
BITFS[1:0] bits. The BICK output will be in two different frequencies if setting BITFS[1:0] bits = 1h
(48kHz) when the sampling frequency is 12kHz, 24kHz, 48kHz or 96kHz (DFS[2:0]). LRCK and BICK are
not output during system reset.
XTI
XTI
External Clock
XTO
AK7755
Figure 17. Using Crystal Oscillator (CKM mode 0/1)
XTO
AK7755
Using External Clock (CKM mode 0/1)
2-2. Slave Mode1 (CKM mode 2: XTI Input Clock）
fs: sampling frequency
CKM CKM XTI
mode [2:0] _fs:48kHz
fs:44.1kHz
Input Frequency Range Use of Chrystal
(MHz)
Oscillator
2
010 12.288MHz 11.2896MHz 11.0 to 12.4
Not Available
Required System Clocks are XTI, LRCK and BICK. XTI and LRCK must be synchronized, but the phase
between these clocks is not important. The system sampling rate is controlled by DFS[2:0] bits. The
sampling frequency of BICK is set by BITFS[1:0] bits.
2-3. Slave Mode 2 (CKM mode 3: BICK Input Clock)
In CKM mode 3, required system clocks are BICK and LRCK. In this mode, BICK is used for clock source
instead of XTI. This clock is multiplied directly by a PLL to generate the master clock (MCLK). Therefore
BICK with two different frequencies cannot be used. BICK and LRCK must be synchronized. Set BICK
frequency for LRCK by BITFS[1:0] bits. The sampling rate is determined by DFS[2:0] bits setting. In
applications which do not need the XTI pin of the AK7755, leave this pin open.
014006643-E-00
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2014/10