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PDF TDA1302T Data sheet ( Hoja de datos )
| Número de pieza | TDA1302T | |
| Descripción | Data amplifier and laser supply circuit for CD player and read only optical systems | |
| Fabricantes | NXP Semiconductors | |
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TDA1302_1 2 Wed Sep 14 13:30:56 1994
Philips Semiconductors
Data amplifier and laser supply circuit for
CD player and read only optical systems
Preliminary specification
TDA1302T
FEATURES
• Six input buffer amplifiers with low-pass filtering and with
virtually no offset
• HF data amplifier with a high or low gain mode
• Two built-in equalizers for single or double-speed mode
ensuring high performance in both modes
• Fully automatic laser control including stabilization and
an ON/OFF switch, plus a separate supply (VDDL) for
power reduction
• Adjustable laser bandwidth and laser switch-on current
slope
• Protection circuit to prevent laser damage due to supply
voltage dip
• Optimized interconnectiion between pick-up detector
and digital servo processor (TDA1301T)
• Wide supply voltage range
• Wide temperature range
• Low power consumption.
GENERAL DESCRIPTION
The TDA1302T is a data amplifier and laser supply circuit
for three-beam pick-up detectors applied in a wide range
of mechanisms for Compact Disc and read only optical
systems. The device contains 6 amplifiers which amplify
and filter the focus and radial diode signals and provides
an equalized RF signal suitable for single or double speed
mode; the mode can be switched by means of the speed
control pin. The device can accommodate astigmatic,
single foucault and double foucault detectors and can be
applied to all N-sub laser/monitor diode units even though
the circuit has been optimized for the Philips CDM12
mechanisms and the digital servo controller TDA1301T.
After a single initial adjustment the circuit will maintain
control over the laser diode current thus resulting in a
constant light output power which is independent of
ageing. The IC is mounted in a small-outline package to
enable it to be mounted close to the laser pick-up unit on
the sledge.
QUICK REFERENCE DATA
SYMBOL
PARAMETER
VDD supply voltage (pin 18)
Diode current amplifiers
Gdn
Ios(d)
B
amplification
diode output offset current
3 dB bandwidth
RFE amplifier (built-in equalizer)
td(eq)
td(f)
equalization delay
flatness delay
Laser supply
Io(l) output current
CONDITIONS
MIN. TYP. MAX. UNIT
3.4 −
5.5 V
Ii(d) = 1.67 µA
− 1.55 − dB
− − 100 nA
50 − − kHz
fi = 0.3 MHz
double-speed
− 320 − ns
− 5 − ns
VDDL = 3 V
− − −100 mA
ORDERING INFORMATION
TYPE NUMBER
TDA1302T
NAME
SO24
PACKAGE
DESCRIPTION
plastic small outline package; 24 leads; body width 7.5 mm
VERSION
SOT137-1
September 1994
2
1 page  
TDA1302_1 6 Wed Sep 14 13:30:56 1994
Philips Semiconductors
Data amplifier and laser supply circuit for
CD player and read only optical systems
Preliminary specification
TDA1302T
FUNCTIONAL DESCRIPTION
The TDA1302T can be divided into two main sections, the
laser control circuit and the photo diode signal filter and
amplification section.
Laser control circuit
The main function of the laser control circuit is to control
the laser diode current in order to achieve a constant light
output power which is based on the current of the monitor
diode which is continuously monitored. The circuit is built
up into three parts.
The first part is the input stage which compares the
monitor diode current with a current which is 10 times the
value of the adjustable current. The adjustable current is
derived from a bandgap reference source, to be
temperature independent, and can be further adjusted by
the external resistor RADJ in order to adapt the circuit to the
parameters of the laser/monitor diode unit to be used. The
difference is fed to the second part.
The second part is the integrator stage which makes use
of an external capacitor CL. This capacitor has two
different functions.
During switch-on of the laser current, it provides a current
slope of typically: dILO/dt ≅ 10−6/CL (A/s).
After switch-on it ensures that the bandwidth conforms to
the typical formula: fB ≅ K × Aext × 90−9/(CL × IMON) (Hz).
where Aext represents the AC gain of an extra loop
amplifier, if applied, and K = dImonitor/dIlaser which is
determined by the laser/monitor unit.
IMON is the average current (pin 17) at typical light
emission power of the laser diode.
The third part is the power output stage, its input being the
integrator output signal. This stage has a separate supply
voltage (VDDL) thereby offering the possibility of reduced
power consumption by supplying this pin with the minimum
voltage necessary.
It also has a laser diode protection circuit which is enabled
prior to the output drive transistor becoming saturated due
to a large voltage dip on VDDL. Saturation will result in a
lower current from the laser diode, which is normally
followed immediately by an increment of the voltage from
the external capacitor CL, which could cause damage to
the laser diode at the end of the voltage dip. The protection
circuit prevents an increment of the capacitor voltage and
thus offers full protection to the laser diode under these
circumstances.
Photo diode signal filter and amplification section
This section has 6 identical current amplifiers. Amplifiers 1
to 4 are designed to amplify the focus photo diode signals.
Each amplifier has two outputs, an LF output and an
internal RF output. Amplifiers 5 and 6 are used for the
radial photo diode currents and have only an LF output. All
6 output signals are low-pass filtered with a corner
frequency at 65 kHz. The internal RF output signals are
summed together and converted into a voltage by means
of a selectable transresistance of 120 kΩ or 240 kΩ. This
signal is available directly at pin 10, however, there is also
an unfiltered signal available at pin 9. The equalization
filter used has 2 different filter curves, one for single-speed
mode and one for double-speed mode.
Table 1 Operational modes.
SWITCH
IF NOT
PIN CONNECTED
DEFAULT
Control pin
HG
LS
LDON
1
1
1
Note
1. Where X = don’t care.
GAIN
HIGH
1
X
X
LOW
0
X
X
MODE(1)
SPEED
SINGLE
X
1
X
DOUBLE
X
0
X
LASER
ON OFF
XX
XX
10
September 1994
6
5 Page 
TDA1302_1 12 Wed Sep 14 13:30:56 1994
Philips Semiconductors
Data amplifier and laser supply circuit for
CD player and read only optical systems
INTERNAL PIN CONFIGURATION
Preliminary specification
TDA1302T
September 1994
Fig.8 Equivalent internal pin diagrams.
12
11 Page | ||
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| PDF Descargar | [ Datasheet TDA1302T.PDF ] | |
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