ak4538 AKM Semiconductor, Inc., ak4538 Datasheet - Page 36

• Manufacturer Part Number: ak4538
• Description: 16bit ?? Codec With Mic/hp/spk-amp
• Manufacturer: AKM Semiconductor, Inc.

ASAHI KASEI
n ALC2 Operation
Input resistance of the ALC2 is 24k (typ) and centered around VCOM voltage, and the input signal level is –3.1dBV. (see
Figure 31. 0dBV=1Vrms=2.828Vpp)
The limiter detection level is proportional to HVDD. The output level is limited by the ALC2 circuit 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.
MS0198-E-01
FS-12dB
FS
Operation Start Level
Period
Zero-crossing Detection
ATT/GAIN
Figure 31. Speaker-amp Output Level Diagram (HVDD=3.3V, DATT= 8.0dB)
Parameter
ROTM bit = “0”
ROTM bit = “1”
-15.3dBV
Table 24. Limiter /Recovery of ALC2 at HVDD=3.3V
-3.3dBV
-8dB
ATT+DAC
-8dB
2/fs = 180 s (at 11.025kHz)
-11.3dBV
2/fs = 45 s (at 44.1kHz)
ALC2 Limiter operation
-23.3dBV
-15.3dBV
-3.3dBV
0.5dB step
+4.1dB
- 36 -
5.2dBV
No
-1.9dB
ALC2
FS-1.9dB = -5.2dBV
+16.1dB
+8.1dB
+5.6dB
SPK-AMP
FS-3.9dB = -7.2dBV
-0.4dB
512/fs=46.4ms (at 11.025kHz)
Yes (Timeout = Period Time)
2048/fs=46.4ms (at 44.1kHz)
ALC2 Recovery operation
0.4dBV
-5.6dBV
-1.6dBV
1dB step
7.2dBV
-10dBV
-20dBV
-30dBV
0dBV
Full-differential
Single-ended
[AK4538]
2003/5