AK4632VN AKM [Asahi Kasei Microsystems], AK4632VN Datasheet - Page 38

• Manufacturer Part Number: AK4632VN
• Description: 16-Bit ?? Mono CODEC with ALC & MIC/SPK/Video-AMP
• Manufacturer: AKM [Asahi Kasei Microsystems]

ASAHI KASEI
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
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.
MS0396-E-00
SPK-ALC Operation
~
Figure 40.
Operation Start Level
Period
Zero-crossing Detection
ATT/GAIN
Table 22. Gain of Speaker-Amp at ALC2 OFF(Full-differential Output)
Parameter
fs=16kHz
fs=8kHz
Table 21. Limiter /Recovery of ALC2 (ROTM bit = “0”)
SPKG1-0 bits
00
01
10
11
ALC2 Limiter operation
2/fs = 250µs
2/fs = 125µs
0.5dB step
−5.2dBV
- 38 -
No
+10.6dB
+12.7dB
+4.4dB
+6.4dB
Gain
Yes (Timeout = Period Time)
ALC2 Recovery operation
512/fs=64ms
512/fs=32ms
−7.2dBV
1dB step
[AK4632]
2005/06