AK4213 Datasheet, PDF (17/38 Pages) Asahi Kasei Microsystems – Mono Class-D SPK-Amp with Stereo Cap-less HP-Amp

[AK4213]
■ ALC Operation
The ALC (Automatic Level Control) operation of speaker-amp output is operated by ALC block when ALC bit = “1”.
When ALC bit is “0”, the speaker volume depends on the setting value of SPGA5-0 bits.
(1) ALC Limiter Operation
During the ALC limiter operation, when ALC output level exceeds the ALC limiter detection level (LMTH bit), the
SPGA value is attenuated automatically to the amount defined by ALC limiter ATT step (LMTH1-0 bits).
When ZELMN bit is set to “0” (zero crossing detection is enabled), the SPGA value is changed by the ALC limiter
operation at the zero crossing point or at the zero crossing timeout. ZTM1-0 bits set the zero crossing timeout periods of
both the ALC limiter and recovery operation.
When ZELMN bit = “1” (zero crossing detection is disabled), SPGA value is immediately (period: typ. 125μs, max.
200μs) changed by ALC limiter operation. Attenuation step is fixed to 1 step regardless of the setting of LMAT1-0 bits.
The attenuate operation is executed continuously until the ALC output level becomes ALC limiter detection level or less.
After completing the attenuate operation, unless ALC bit is changed to “0”, the operation repeats when the input signal
level exceeds LMTH bit.
LMTH bit ALC Limiter Detection Level ALC Recovery Waiting Counter Reset Level
0
ALC Output ≥ -7.5dBV
−7.5dBV > ALC Output ≥ −9.5dBV
1
ALC Output ≥ -11.5dBV
−11.5dBV > ALC Output ≥ −13.5dBV
Note: ALC limiter detection level and ALC recovery waiting counter reset level do not depend
on operation voltage.
Table 5. ALC Limiter Detection Level / Recovery Counter Reset Level
(default)
ZELMN bit
0
1
LMAT1 LMAT0
ALC Limiter ATT Step
0
0
1 step
0.5dB
0
1
2 step
1.0dB
1
0
4 step
2.0dB
1
1
8 step
4.0dB
x
x
1step
0.5dB
Table 6. ALC Limiter ATT Step (x: Don’t care)
(default)
ZTM1 bit ZTM0 bit
Zero Crossing Timeout
typ.
max
0
0
16.4ms
26.3ms
0
1
32.8ms
51.5ms (default)
1
0
65.6ms
105.0ms
1
1
131.2ms
210.0ms
Table 7. ALC Zero Crossing Timeout Period
MS0949-E-01
- 17 -
2008/07