參數(shù)資料
型號: AK4561
廠商: Asahi Kasei Microsystems Co.,Ltd
元件分類: Codec
英文描述: 16bit CODEC with built-in ALC and MIC/HP-Amp
中文描述: 16位編解碼器在ALC和內置麥克風/惠普放大器
文件頁數(shù): 38/48頁
文件大小: 332K
代理商: AK4561
ASAHI KASEI
AKM CONFIDENTIAL
[AK4561]
Rev. 0.9
2000/09
- 38 -
n
ALC Operation
1. ALC Limiter Operation
During the ALC limiter operation, when either Lch or Rch exceed ALC limiter detection level (LMTH), IPGA value is
attenuated by ALC limiter ATT step (LMAT1-0) automatically. Then the IPGA value is changed commonly for L/R
channels.
In case of ZELM = “0”, timeout period is set by LTM1-0 bits. The operation for attenuation is done continuously until the
input signal level becomes LMTH or less. After finishing the operation for attenuation, if ALC bit does not change into
“0”, the operation of attenuation repeats when the input signal level exceed LMTH. (Refer to Figure 26)
In case of ZELM = “1”, timeout period is set by ZTM1-0 bits. The IPGA value is attenuated by zero crossing detection
automatically. (Refer to Figure 27)
When FR bit is “0”, the ALC operation corresponds to the impulse noise in additional to the ALC operation of AK4516A.
When the impulse noise is input, the ALC recovery operation becomes the faster period than a normal recovery operation.
When FR bit is “1”, the ALC operation in AK4561 is the same as AK4516A’s.
[Explanation for ALC operation]
Recovery waiting counter
reset level (LMTH)
Limiter detection level(LMTH)
ATT level (LMAT1-0)
(1) 2dB
ATT level (LMAT1-0)
ATT level (LMAT1-0)
Limiter update period (LTM1-0)
Limiter finish
Limiter starts
Figure 26. Disable ALC zero crossing detection (ZELM = “0”)
(1). When the signal is input between 2dB, the AK4561 does not operate the ALC limiter and recovery.
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