ASAHI KASEI
[AK4387]
OPERATION OVERVIEW
System Clock
The external clocks, which are required to operate the AK4387, 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. There are two methods to set MCLK frequency. In Manual Setting Mode (ACKS bit
= “0”: Register 00H), the sampling speed is set by DFS0/1(Table 1). The frequency of MCLK at each sampling speed is
set automatically. (Table 2~4). After exiting reset (RSTN pin = “ ”), the AK4387 is in Auto Setting Mode. In Auto
↑
Setting Mode (ACKS bit = “1”: Default), as MCLK frequencyis detected automatically (Table 5), and the internal master
clock becomes the appropriate frequency (Table 6), it is not necessary to set DFS0/1.
All external clocks (MCLK, BICK and LRCK) should always be present whenever the AK4387 is in the normal operation
mode (RSTN pin = ”H”). If these clocks are not provided, the AK4387 may draw excess current and may fall into
unpredictable operation. This is because the device utilizes dynamic refreshed logic internally. The AK4387 should be
reset by RSTN pin = “L” after threse clocks are provided. If the external clocks are not present, the AK4387 should be in
the power-down mode (RSTN pin = “L”). After exiting reset at power-up etc., the AK4387 is in the power-down mode
until MCLK and LRCK are input.
DFS1
DFS0
Sampling Rate (fs)
Default
0
0
1
0
1
0
Normal Speed Mode
8kHz~48kHz
60kHz~96kHz
120kHz~192kHz
Double Speed Mode
Quad Speed Mode
Table 1. Sampling Speed (Manual Setting Mode)
LRCK
fs
MCLK
512fs
BICK
64fs
8.1920MHz 12.2880MHz 16.3840MHz 24.5760MHz 36.8640MHz 2.0480MHz
256fs
384fs
768fs
1152fs
32.0kHz
44.1kHz 11.2896MHz 16.9344MHz 22.5792MHz 33.8688MHz
48.0kHz 12.2880MHz 18.4320MHz 24.5760MHz 36.8640MHz
N/A
N/A
2.8224MHz
3.0720MHz
Table 2. System Clock Example (Normal Speed Mode @Manual Setting Mode)
LRCK
fs
MCLK
BICK
64fs
128fs
192fs
256fs
384fs
88.2kHz 11.2896MHz 16.9344MHz 22.5792MHz 33.8688MHz 5.6448MHz
96.0kHz 12.2880MHz 18.4320MHz 24.5760MHz 36.8640MHz 6.1440MHz
Table 3. System Clock Example (Double Speed Mode @Manual Setting Mode)
MS0429-E-00
2005/09
- 8 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
