Samsung DVD-907 Service Manual page 71

7-2 RF circuit description
7-2-1 RIC1(TA1236F)
TA1236F is combined with TA1253FN, TC9240F and TC90A19F as bipolar IC developed for DVD SERVO system.
Main features include DVD waveform equalizing, CD waveform equalizing, focus error signal generation, 3-beam
tracking error signal generation, laser power control, etc. after receiving the pick-up output converted into I/V.
7-2-1(a) Basic potentiometer
TA1236F uses a single power method and each circuit is based on V
symmetrical about GND for V because V
REF REF
and 2V output(pin18).
REF
7-2-1(b) RF signal
Fig. 7-11 shows the flow of signal generated by the pick-up.
A, B, C, D signals detected from pick-up are converted in to RF signal(A+B+C+D) via RF summing AMP.
RF signal is inputted to RFN(pin55) among input terminals and RFP(pin54) is used for AC ground.
PICK-UP
RC12
104
RC10
104
D A
PD
C B
RC15
104
RC14
104
I-V AMP
Fig. 7-12 shows the waveform-equalizing block diagram for the RF signal.
It outputs to EQout(pin 46) terminal by initially changing switching AMP gain of DVD and CD, and then
adjusting the level in VCA. It controls VCA gain by means of RF gain(pin 48) and interfaces with PWM signal,
(output from RFGC terminal of TC9420F, via low-pass filter to constitute a loop for adjustment of constant
amplitude). The gain in EQout is 1.0 for DVD and 1.67 for CD.
EQout terminal is connected with EQin(pin 45) externally, and inputs into DVD EQ and CD EQ(Waveform
equalizing circuit).
7-6
of 2.1V. Note :
REF
(pin20) terminal is needed for IC, which uses the peripheral V
SUMMING AMP
RR18
1.2K
RR20
RIC3 OPA650
1K
RC11
2
–
104
6
3
+ +5A
RR19
1K
RR23
10K
RR50
5.6K
Vref
RR24
RR51
1K
5.6K
RR22
1K
RC22 RR33
104 10K
Vref
Fig. 7-11
Samsung Electronics
REF
The control parameters of DVD EQ and CD EQ are as follows.
1) DVD EQ control parameter
- DVDEQ(pin 43)
- DVDTIME(pin 41) : Changes the peak frequency with EQ frequency characteristic. Convert PWM signal,
55 RFN
- S/Dse1(pin 64)
- MCK(pin 15)
RIC1
- DVDGD(pin 25)
TA1236
2) CD EQ control parameter
RFP
54
- CD EQ(pin 40)
- CD TIME(pin 42) : Changes the peak frequency with EQ frequency characteristic. The constant DC is
- S/Qse1(pin 44)
CD and DVD signals are equalized according to the above control parameters ,and then output to CD
EQ OUT (pin39) and DVD EQ OUT (pin34). Then, CD signal is transferred to TC9420F (pin 38), DVD
signal is sent to TC90A19F(pin 50) and detected.
Samsung Electronics
CD CD
DVDsel RFgain EQout EQin
EQ TIME
47 48 46 45 40 42
55
RFN
ATT CD EQ
VCA
54
RFP
DVD EQ
RIC1
TA1236F
64 41 43
SDsel DVD DVD
TIME EQ
Fig. 7-12
: Changes the gain of peak frequency with EQ frequency characteristic. Convert PWM
signal, output from TC90A19F, into DC via low-pass filter.
output from TC90A19F, into DC via low-pass filter.
: Changes the peak frequency (like DVD TIME) as 2d control. ( Switched according to
regeneration speed ratio of single/double layer).
: Input the base clock and link the peak frequency with it. The amplitude of MCK might be
small (500mVp-p).
: Changes the group delay characteristics with EQ frequency characteristic.
: Changes the gain of peak frequency with EQ frequency characteristic. The constant DC
is supplied to a resistive voltage divider.
supplied to a resistive voltage divider.
: Changes the peak frequency (such as CD TIME) as 2d control. (Switched according to
play linear velocity ratio of quadruple/single rate. Set to '0' because only one rate is
vaild in this system).
Circuit Descriptions
SQsel
44
39
CD EQ OUT
25
DVD G/D
34
DVD EQ OUT
GEN.
T/CON
15
MCK
7-7