AK4632 Datasheet, PDF (38/70 Pages) Asahi Kasei Microsystems – 16-Bit ΔΣ Mono CODEC with ALC & MIC/SPK/Video-AMP

ASAHI KASEI
[AK4632]
„ SPK-ALC Operation
The ALC (Automatic Level Control) operation of speaker output is done by ALC2 block when ALC2 bit is “1”. Input
resistance of the ALC2 is 24kΩ (typ) and centered around VCOM voltage. The ALC2 level diagram is shown in Figure
37 ~Figure 40.
The limiter detection level is proportional to SVDD voltage. The output level is limited by the ALC2 circuit when the
input signal exceeds –7.1dBV (@SPKG1 bit = “0”, SVDD=3.3V or @SPKG1 bit = “1”, SVDD = 5V). When a
continuous signal of –7.1dBV or greater is input to the ALC2 circuit, the change period of the ALC2 limiter operation is
250µs (=2/fs@fs=8kHz) and the attenuation level is 0.5dB/step.
The ALC2 recovery operation uses zero crossings and gains of 1dB/step. The ALC2 recovery operation is done until the
input level of the Speaker-amp goes to –9.1dBV (@SPKG1 bit = “0”, SVDD=3.3V or @SPKG1 bit = “1”, SVDD = 5V).
Maximum gain of the ALC2 recovery operation is set by RFS5-0 bits.
When the input signal is between –9.1dBV and –7.1dBV, the ALC2 limiter or recovery operations are not done.
When the PMSPK bit changes from “0” to “1”, the initilization cycle (512/fs = 64ms @fs=8kHz at ROTM bit = “0”) starts.
The ALC2 is disabled (The ALC2 gain is fixed to “-3.5dB”.) during the initilization cycle and the ALC2 starts from
“–2dB” after completing the initilization cycle. The ROTM bit and RFS5-0 bits set during the PMSPK bit = “0”.
When the ALC2 is disable, a gain of the ALC2 block is fixed to -3.5dB. Therefore, a gain of internal speaker block is
shown in Table 22.
Parameter
ALC2 Limiter operation
ALC2 Recovery operation
Operation Start Level
−5.2dBV
−7.2dBV
Period
fs=8kHz
fs=16kHz
2/fs = 250µs
2/fs = 125µs
512/fs=64ms
512/fs=32ms
Zero-crossing Detection
No
Yes (Timeout = Period Time)
ATT/GAIN
0.5dB step
1dB step
Table 21. Limiter /Recovery of ALC2 (ROTM bit = “0”)
SPKG1-0 bits
Gain
00
+4.4dB
01
+6.4dB
10
+10.6dB
11
+12.7dB
Table 22. Gain of Speaker-Amp at ALC2 OFF(Full-differential Output)
MS0396-E-00
- 38 -
2005/06