Technics SL-P222A - Page 43

3-2 TDA8809 RADIAL ERROR PROCESSOR
TDA8809
Gain Control
Circuit
eo
Rel Rel Re2 Re2
2 2
Rel + Re2
Input Mirror
Vref 5V
eThe resistor R3535 sets the amount of
output current of the DAC signal.
eThe other components’ setting the
oscillator frequency are R3530, R3531,
C2530, C2531.
@®The inputs BO - B3 are used to control
the operations which have to be
performed by the radial error
processor.
eThe DAC output is a current source
output used to move the radial arm.
The normal control is RE, but to jump
beyond tracks and to compensate bumps
the DAC signal is used.
®The RE lag output gives the loop a
more powerful control.
This output is only activated during
normal playback.
eThe RE dig is a 11-bit quantized
version of the RE signal. The function
of RE dig is not in all sets the same.
Below is the function in a _ audio
Player explained. If a TL occurs the
Microprocessor looks to RE dig, the
value of RE dig indicates whether the
microprocessor has to compensate for a
right or left bump via DAC . The
Maximum hold range of RE is normally
— 53 —
=> o> @)
SP I lh
SL-P222A
Circuit
i
£0
Radial 9
Radial Motor
p&—-Current Selector for
Optical Arm (4 bit Data)
1/4 track pitch due to the sinusoidal
form of the radial error signal. By
means of TL and RE dig the hold range
is extended to 3/4 track pitch.
eFor high speed track crossing, four
dived RE dig signal is given by
pulling Div 4 input to low level.
3-2-1 Radial processing
The
radial
error
processor
has
to
process
the
basic
input
signals
RE1
and
RE2
and
to
generate
the
full
radial
error
signal
RE.
The
RE
ssignal
is
the
basic
signal
to
keep
the
reading
beam
on
track.
RE1
and
RE2
are
caused
by
more
az
less
light
of
the
laser
failing
onto
diodes
D1,
D2
or
D3,
D4
(see
figure
below)
RADIAL
TRRACKING
tRRROR
0) 14+D2) —
(03+D4)
Di D2 D3 D4
PIT
TRACK
SHIFTS
LEFT
ON TRACK D.
3
iF . SIGNALS
D4 (1 +D2+D3+D4
TRACK SHIFTS RIGHT
RE1 = 11412 and RE2 = i3+i4