LA9702W Datasheet, PDF (5/10 Pages) Sanyo Semicon Device – DVD Player Front End Processor

LA9702W
7. FE amplifier
The signal input from either pins 3, 4, 5, and 6 or pins 8 and 9 is first passed through an offset adjustment circuit and is
then passed through a balance adjustment VCA. Then either the calculation <(pin 3 + pin 5) – (pin 4 + pin 6)> or <pin
8 – pin 9> is performed. The result is passed through the servo gain adjustment VCA and output from pin 29. The gain
of the balance adjustment VCA is adjusted by the DC voltage input to pin 19. The offset adjustment can be adjusted by
the DC voltage applied to pin 23. The VCA that adjusts the servo gain is controlled by the DC voltage applied to pin
18.
Note that when the pin 76 input is high, pins 3, 4, 5, and 6 are selected, and when low, pins 8 and 9 are selected.
8. TE amplifier (for three-beam operation)
The current signal input to pin 10 and 11 is converted from a current to a voltage, passed through an offset adjustment
circuit, and passed through a balance adjustment VCA. Then the calculation <pin 11 – pin 10> is performed and the
result passed through a servo gain adjustment VCA. The result is output from pin 30 after band switching. The offset
adjustment can be adjusted by the DC voltage applied to pin 24. The gain of the balance adjustment VCA can be
adjusted by the DC voltage applied to pin 20. The VCA that adjusts the servo gain is controlled by the DC voltage
applied to pin 18. The band switching circuit is a low-pass filter with a cutoff frequency of 30 kHz when pin 57 is high
and 100 kHz when pin 57 is low. When pin 53 is low, pin 30 operates in hold mode.
Note that the three-beam TE is used when pin 68 is low.
9. DPD circuit
The phases of the signals input to pins 1 and 2, and the signals input to pins 3, 4, 5, and 6 are compared and the result
outputs from pin 30.
The phase comparison result signal is output as a current by the pin 38 constant-current charge pump and converted to
a voltage level by the external capacitor and resistor on pin 38. The voltage-converted signal is passed through a buffer
amplifier, is band limited by a band switching circuit, and is output from pin 30. The charge pump is turned off when
pin 51 is high. The band switching circuit is a low-pass filter with a cutoff frequency of 30 kHz when pin 57 is high
and 100 kHz when pin 57 is low. When pin 53 is low, pin 30 operates in hold mode.
Note that the DPD circuit is used when pin 63 will be high.
10. PP amplifier
The signals input to pins 3, 4, 5, and 6 are passed first through an offset adjustment circuit and then through a balance
adjustment VCA. The calculation <(pin 3 + pin 6) – (pin 4 – pin 5)> is performed. The result is passed through a servo
gain adjustment VCA and is output from pin 35 after band switching. The offset adjustment can be adjusted by the DC
voltage applied to pin 24. The gain of the balance adjustment VCA can be adjusted by the DC voltage applied to pin
20. The VCA that adjusts the servo gain is controlled by the DC voltage applied to pin 18.
Note that the PP amplifier is used when pin 68 will be high.
11. Wobble bandpass filter
The signal input to pin 34 is passed through a bandpass filter and output from pin 32. The frequency fo for the
bandpass filter can be modified with the external resistor on pin 33. When the pin 33 external resistor is 62 kΩ, fo will
be about 200 kHz.
12. APC circuit
A servo loop that holds the laser power fixed can be formed by inputting a monitor signal to pin 14 and connecting the
laser driver to pin 13. The laser can be turned off by setting pin 72 low.
Note that there are two APC systems, with the other system consisting of pin 16 as the monitor input pin, pin 15 as the
drive pin, and pin 70 as the laser off control pin.
13. Reference circuit
A voltage that is created by resistor dividing V_CC by 2 is output from pin 26. The pin 26 voltage is buffered and output
from pins 79 and 27. The pin 79 voltage is a special-purpose reference voltage only for use by the pickup, and the pin
27 voltage is a reference supplied to the DSP and other systems.
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