Philips TDA1302T Datasheet

TDA1302_1 2 Wed Sep 14 13:30:56 1994

Philips Semiconductors Preliminary speciﬁcation

Data ampliﬁer and laser supply circuit for CD player and read only optical systems

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 (V

DDL

) 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

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.

TDA1302T

• Low power consumption.

QUICK REFERENCE DATA

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

supply voltage (pin 18) 3.4 − 5.5 V

Diode current ampliﬁers

os(d)

B 3 dB bandwidth I

ampliﬁcation − 1.55 − dB diode output offset current − − 100 nA

= 1.67 µA 50 − − kHz

i(d)

RFE ampliﬁer (built-in equalizer)

d(eq)

d(f)

equalization delay fi= 0.3 MHz − 320 − ns ﬂatness delay double-speed − 5 − ns

Laser supply

o(l)

output current V

= 3 V − − −100 mA

DDL

ORDERING INFORMATION

TYPE NUMBER

NAME DESCRIPTION VERSION

PACKAGE

TDA1302T SO24 plastic small outline package; 24 leads; body width 7.5 mm SOT137-1

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Philips Semiconductors Preliminary speciﬁcation

Fig.1 Schematic diagram for CD player.

Data ampliﬁer and laser supply circuit for CD player and read only optical systems

SCHEMATIC DIAGRAM

TDA1302T

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TDA1302_1 3 Wed Sep 14 13:30:56 1994

TDA1302_1 4 Wed Sep 14 13:30:56 1994

Fig.2 Block diagram.

Philips Semiconductors Preliminary speciﬁcation

Data ampliﬁer and laser supply circuit for CD player and read only optical systems

BLOCK DIAGRAM

TDA1302T

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TDA1302_1 5 Wed Sep 14 13:30:56 1994

Fig.3 Pin configuration.

Philips Semiconductors Preliminary speciﬁcation

Data ampliﬁer and laser supply circuit for CD player and read only optical systems

PINNING

SYMBOL PIN DESCRIPTION

O4 1 output of diode current ampliﬁer 4 O6 2 output of diode current ampliﬁer 6 O3 3 output of diode current ampliﬁer 3 O1 4 output of diode current ampliﬁer 1 O5 5 output of diode current ampliﬁer 5 O2 6 output of diode current ampliﬁer 2 LDON 7 control pin for switching the laser

ON and OFF

DDL

RFE 9 equalized output voltage of sum

RF 10 unequalized output HG 11 control pin for gain switch LS 12 control pin for speed switch CL 13 external capacitor ADJ 14 reference input normally

GND 15 0 V supply; substrate connection

LO 16 current output to the laser diode MI 17 laser monitor diode input V

I2 19 photo detector input 2 (central) I5 20 photo detector input 5 (satellite) I1 21 photo detector input 1 (central) I3 22 photo detector input 3 (central) I6 23 photo detector input 6 (satellite) I4 24 photo detector input 4 (central)

8 laser supply voltage

signal of ampliﬁers 1 to 4

connected to ground via a resistor

(ground)

18 ampliﬁer supply voltage

TDA1302T

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TDA1302_1 6 Wed Sep 14 13:30:56 1994

Philips Semiconductors Preliminary speciﬁcation

Data ampliﬁer and laser supply circuit for CD player and read only optical systems

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 R 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 × A

where A

represents the AC gain of an extra loop

ext

amplifier, if applied, and K = dI determined by the laser/monitor unit.

is the average current (pin 17) at typical light

MON

emission power of the laser diode.

in order to adapt the circuit to the

ADJ

× 90−9/(CL × I

ext

monitor

/dI

laser

MON

which is

) (Hz).

TDA1302T

The third part is the power output stage, its input being the integrator output signal. This stage has a separate supply voltage (V 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 V 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.

) thereby offering the possibility of reduced

DDL

. Saturation will result in a

DDL

Table 1 Operational modes.

IF NOT

SWITCH PIN

CONNECTED

DEFAULT

GAIN SPEED LASER

HIGH LOW SINGLE DOUBLE ON OFF

HG 1 1 0 X X X X

Control pin

LS 1 X X 1 0 X X LDON 1 X X X X 1 0

Note

1. Where X = don’t care.

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MODE

(1)

TDA1302_1 7 Wed Sep 14 13:30:56 1994

Philips Semiconductors Preliminary speciﬁcation

Data ampliﬁer and laser supply circuit for CD player and read only optical systems

TDA1302T

LIMITING VALUES

In accordance with the Absolute Maximum Rating System (IEC 134).

SYMBOL PARAMETER MIN. MAX. UNIT

tot

stg

amb

supply voltage − 8.0 V total power dissipation − 300 mW storage temperature −65 +150 °C operating ambient temperature −40 +85 °C

HANDLING

Classification A: human body model; C = 100 pF; R = 1500 Ω; V = ± 2000 V. Charge device model: C = 200 pF; L = 2.5 µH; R = 0 Ω; V = 250 V.

THERMAL RESISTANCE

SYMBOL PARAMETER THERMAL RESISTANCE

th j-a

from junction to ambient in free air 60 K/W

QUALITY SPECIFICATION

In accordance with

“SNW-FQ-611 part E”

Reference Handbook”

. The handbook can be ordered using the code 9398 510 63011.

. The numbers of the quality specification can be found in the

“Quality

CHARACTERISTICS

VDD= 3.4 V; V (R

= 750 Ω, C

ext

= 2.5 V; T

DDL

= 47 pF) at pin 9; unless otherwise speciﬁed.

ext

= 25 °C; R

amb

= 48 kΩ; HG = logic 1; LS = logic 1; with an external LP ﬁlter

ADJ

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

Supply

DDL

diss

ampliﬁer supply current laser OFF − 8 − mA ampliﬁer supply voltage 3.4 − 5.5 V laser control supply voltage 2.5 − 5.5 V power dissipation laser OFF; VDD= 3.4 V − 27 − mW

Diode current ampliﬁers (1 to 6)

i(d)

o(d)

os(d)

o(d)

B 3 dB bandwidth I G

diode input current note 1 − − 10 µA equivalent noise input − 1 − pA/√Hz diode input voltage I

= 1.67 µA − 0.9 − V

i(d)

diode output voltage −0.2 − VDD− 1 V ampliﬁcation I

diode output offset current I output impedance Idi= 1.67 µA; V

mismatch in ampliﬁcation Idi= 1.67 µA;

= 1.67 µA;

i(d)

= 0 V; note 2

o(dn)

= I

csin

i(d)

= 0; note 3 − − 100 nA

tsin

o(dn)

= 1.67 µA 50 68 − kHz

1.43 1.55 1.67 dB

= 0 V 500 − − kΩ

− − 3 %

= V

o(dn)

o(dm)

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