cxa1992br Sony Electronics, cxa1992br Datasheet - Page 30

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cxa1992br

Manufacturer Part Number
cxa1992br
Description
Rf Signal Processing Servo Amplifier
Manufacturer
Sony Electronics
Datasheet

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1-1. FS4
This switch is provided between the focus error input and the focus phase compensation, and is in charge of
turning the focus servo ON and OFF.
1-2. Procedure of focus activation
For description, suppose that the polarity is as described below.
a) The lens is searching the disc from far to near;
b) The output voltage (Pin 6) is changing from negative to positive; and
c) The focus S-curve is varying as shown below.
The focus servo is activated at the operating point indicated by A in Fig. 3. Ordinarily, focus searching and the
turning the focus servo switch ON are performed during the focus S-curve transits the point A indicated in Fig.
3. To prevent misoperation, this signal is ANDed with the focus OK signal.
In this IC, FZC (Focus Zero Cross) signal is output from the SENS1 pin (Pin 25) as the point A transit signal.
In addition, focus OK is output as a signal indicating that the signal is in focus (can be in focus in this case).
Following the line of the above description, focusing can be well obtained by observing the following timing
chart.
$00
Focus off
Drive voltage
Focus error
Focus OK
SENS1
(FZC)
$08
Focus on
($00)
(20ms) (200ms)
$02
Fig. 4. Focus ON timing chart
$03
Fig. 3. S-curve
– 30 –
The instant when the signal is brought into focus.
$08
A
t
The broken lines in the figure
indicate the voltage assuming
the signal is not in focus.
CXA1992BR

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