Samsung DVD-P355B/XEH, DVD-P355B/XEU, DVD-P355B/XEG Operation, Focusing Servo, Tracking Servo

Circuit Operating Descriptions

13-4-3 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 167 of ZIC1 during Focus SERVO ON.) At that time, S curve is input to pin 181 of ZIC1.

PZ (pin 183 of ZIC1) 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).

Pin 167 of ZIC1 (FOD) Vref

Pin 181 of ZIC1 (FE) Vref

Pin 183 of ZIC1 (AAF_PZ) 1.5V

Fig. 13-15

(2) PLAY

When focus loop closes the loop during focus servo on, both are controlled by VREF voltage (approx. 1.65V).

2) TRACKING SERVO

(1) NORMAL PLAY MODE

ŒFor DVD

Composite : The signal output from PD A, B, C, D of Pick-up, the tracking error signal (pin39 of RIC1) uses the phase difference of A+C and B+D in RIC1, and inputs to ZIC1. Then, it is output to ZIC1 pin 169 via digital equalizer, and applied to the tracking actuator through FIC3.

Pin 69 of ZIC1 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 ZIC1. The tracking error signal is similar to DVD.

Samsung Electronics 13-11