
ASAHI KASEI 
[AK4702EQ] 
MS0424-E-00 
2005/09 
- 19 - 
 Zero-cross Detection and Offset Calibration 
To minimize the click noise when changing the gain of volume#1, the AK4702 has a zero-cross detection and an offset 
calibration function. 
1. Zero-cross detection function 
When the ZERO bit = “1”, the zero-cross detection function is enabled. The gain of volume#1 changes at the first 
zero-cross point from the acknowledgement of a volume changing command or when the zero-cross is not detected within 
the time set by ZTM1-0 bits (256/fs to 2048/fs). The zero-cross counter is initialized whenever a gain is issued. The 
zero-cross is detected on L/R channels independently. To disable this function, set the ZERO bit to “0”. 
ZERO: Zero-cross detection enable for volume#1 
  0   :   Disable. The volume value changes immediately without zero-cross. 
  1   :   Enable (default). The volume value changes at a zero-crossing point or when timeout (ZTM1-0 bit 
setting) occurs. 
The internal comparator for zero-cross detection has a small offset. Therefore, the gain of volume #1 may change due to 
a zero-cross timeout before the comparator-based zero-cross detection occurs. 
When the new gain value 1EH(-2dB) is written while the gain of both Lch and Rch are 1FH(0dB), if the Lch detects the 
zero-cross prior to Rch, only the gain of Lch changes to 1EH(-2dB) while Rch waits for a zero-cross. After that, if the gain 
is set to 1DH(-4dB) before either a zero-cross or zero-cross timeout, the Rch keeps the same value and changes from 1FH 
to 1DH at next zero-cross or timeout. 
WR[Gain=1EH] 
WR[Gain=1DH]
1FH
Lch Gain 
Rch Gain 
Gain Registers 
Zero-cross 
1FH
1EH
1DH 
1DH
1EH
1FH
1DH
zero-cross timer initialized 
Timeout;  
 (may have click noise)
Timer (256/fs to2048/fs) 
Figure 6. Zero-cross Operation (ZERO= “1”) 
2. Offset calibration function 
Offset calibration is enabled when the CAL bit = “1”. This function begins when the TVOUT source is switched to DAC 
after the STBY bit is changed to “0”. It takes 1664/fs to execute the offset calibration cycle. During the offset calibration 
cycle, the analog outputs are muted. Once the offset calibration is executed, the calibration memory is held until PDN= 
“L” or the new calibration is executed. When the switch is changed from DAC to VCR during calibration, the calibration 
is discontinued, and resumed when TVOUT is switched back to DAC. If volume#1 gain is changed during calibration, the 
change takes place after calibration is complete. 
 Standby Mode 
When the MUTE bit = “0” and the STBY bit = “1”, the AK4702 is forced into TV-VCR loop through mode. In this mode, 
the sources of TVOUTL/R and MONOOUT are fixed to VCRINL/R, the sources of VCROUTL/R are fixed to TVINL/R 
respectively. The gain of volume#1 is fixed to 0dB. Since all registers are NOT initialized by STBY= “1”, a register 
switch configuration requires standby mode (STBY= “0”).