Samsung DVD-E234, Manual

Page: 41 / 64

Circuit Operating Descriptions
Samsung Electronics 7-11
7-4-3 Operation
1) FOCUSING SERVO
(1) FOCUS INPUT
The focus loop is changed from open loop to closed loop, and the triangular waveform moves the object lens up
and down (at pin 13 of SIC1 during Focus SERVO ON.) At that time, S curve is input to pin 8 of SIC1.
ABCD (pin 34 of RIC1) signal, summing signal of PD A, B, C, D, is generated, and zero cross(1.65V) point occurs
when S curve is focused and ABCD signal exceeds a preset,constant value. The focus loop is changed to
closed loop, and the object lens follows the disc movement, maintaining a constant distance from the disc.
(these operations are same in CD and DVD).
Fig. 7-16
Vref
Vref
1.5V
Pin13 of SIC1 (FOD)
Pin8 of RIC1 (ABCD)
Pin39 of SIC1 (FEL)
(2) PLAY
When focus loop closes the loop during focus servo on, both pin 65 and pin 75 of SIC1 are controlled by VREF
voltage (approx. 1.65V), and pin 26, 27 of SIC3 are approximately 2.5V.
2) TRACKING SERVO
(1) NORMAL PLAY MODE
ΠFor DVD
Composite : The signal output from PD A, B, C, D of Pick-up, the tracking error signal (pin31 of RIC1) uses the
phase difference of A+C and B+D in RIC1, and inputs to terminal 3 of SIC1. Then, it is output to SIC1 pin 14 via
digital equalizer, and applied to the tracking actuator through SIC3.
Pin 14 of SIC1 is controlled by VREF(approx. 1.65V) during normal play.
Meanwhile, DVD repeats the track jump from 1 to 4 in inner direction at normal play (because data- read speed
from disc is faster than data output speed on screen).
´ For CD, VCD
Receive the signal output through E, F of Pick-up, from RIC1. The tracking error signal is similar to DVD.