CXA1782CQ/CR
Tracking Automatic Adjustment for Gain/Balance
µ-CON
TZC DFCT FZC
SENS
BUFFER
AMP
Balance OK
Gain OK
24
23
100k
150k
LPF
LPF
HPF
42
43
LPFI
TEO
C. OUT
Frequency
check
–
+
Balance
Gain
Resistance
switching
The CXA1782 has balance control, gain control, and comparator circuits required to perform tracking
automatic adjustment. LPF is set externally at approximately 100Hz.
• Balance adjustment
This adjustment is performed by routing the tracking error signal (TE signal) through the LPF, extracting the
offset DC, and comparing it to the reference level.
However, the TE signal frequency distribution ranges form DC to 2kHz. Merely sending the signal through
the LPF leaves lower frequency components, and the complete DC offset can not be extracted. To extract it,
monitor the TE signal frequency at all times, and perform adjustment only when, a frequency that can lower a
sufficient gain appears on the LPF. Use the C. OUT output to check this frequency.
• Gain adjustment
This adjustment is performed by passing the TE signal through the HPF and comparing the AC component to
the reference level. The HPF signal is implemented by taking the difference between the TE signal and the
LPF component input to Pin 43.
The comparison signal is output from Pin 24 (SENS). Address 3 selects the automatic adjustment
comparator output, and HPF for data (D3) = 1 or LPF for data (D3) = 0 is selected.
• The anti-shock circuit always operates in the CXA1782 so that TG1 and TG2 (address 1 : D3) should be set
to 1 for tracking adjustment to prevent this effect.
When the anti-shock function is not used, Pin 45 (ATSC) should be fixed to VC.
– 16 –
ETC [ ETC ]
