AK4640VG Asahi Kasei Microsystems, AK4640VG Datasheet - Page 40

• Manufacturer Part Number: AK4640VG
• Description: 16BIT CODEC WITH MIC /HP/SPK-AMPl
• Manufacturer: Asahi Kasei Microsystems

ASAHI KASEI
Input resistance of the ALC2 (MIN pin) is 24kΩ (typ) and centered around VCOM voltage. (see Figure 29. 0dBV=1Vrms
=2.828Vpp)
The limiter detection level is proportional to HVDD. The ALC2 circuit limits the output level when the input signal
exceeds –5.2dBV (=FS−1.9dB@HVDD=3.3V). When a continuous signal of –5.2dBV or greater is input to the ALC2
circuit, the change period of the ALC2 limiter operation is set by the ROTM bit 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 –7.2dBV(=FS-3.9dB@HVDD=3.3V). The ROTM bit sets the ALC2 recovery
operation period.
When the input signal is between –5.2dBV and –7.2dBV, the ALC2 limiter or recovery operations are not done.
When the PMSPK bit changes from “0” to “1”, the initilization cycle (2048/fs = 46.4ms @fs=44.1kHz at ROTM bit =
“0”, 512/fs = 11.4ms @fs=44.1kHz at the ROTM bit = “1”) starts. The ALC2 is disabled during the initilization cycle and
the ALC2 starts after completing the initilization cycle.
MS0273-E-00
ALC2 Operation
Operation Start Level
Period
Zero-crossing Detection
ATT/GAIN
FS
FS-12dB
Figure 29. Speaker-amp Output Level Diagram (HVDD=3.3V, DATT=−8.0dB, ALC2= “1”)
Parameter
ROTM bit = “0”
ROTM bit = “1”
-15.3dBV
-3.3dBV
-8dB
DATT
DAC
-8dB
Table 23. Limiter /Recovery of ALC2 at HVDD=3.3V
-3.3dBV
-11.3dBV
-15.3dBV
-23.3dBV
2/fs = 181µs@fs=11.025kHz
2/fs = 45µs@fs=44.1kHz
ALC2 Limiter operation
+4.1dB
ALC2
-1.9dB
0.5dB step
+16.1dB
−5.2dBV
FS-1.9dB = -5.2dBV
Disabled
- 40 -
+8.1dB
FS-3.9dB = -7.2dBV
+8.2dB
SPK-AMP
+2.2dB
+2.2dB
+8.2dB
512/fs = 46.4ms@fs=11.025kHz
2048/fs = 46.4ms@fs=44.1kHz
Enabled (Timeout = 2048/fs)
-3.0dBV
-5.0dBV
3.0dBV(250mW@8ohm)
1.0dBV
ALC2 Recovery operation
-10dBV
-20dBV
-30dBV
−7.2dBV
1dB step
0dBV
Full-differential
Single-ended
[AK4640]
2004/03