1998 Oct 30

Philips Semiconductors

Product specification

Data amplifier and laser supply circuit for CD
audio and video optical systems (ADALAS)

TZA1024

FEATURES

Supports a wide range of voltage output mechanisms

RF amplifier designed for audio and video applications
with data rates up to a maximum of n = 4 times speed

Programmable RF gain for CD-Audio/Video (CD-A/V)
and CD-Read/Write (CD-R/W) discs

Adjustable equalizer for n = 1 or n = 2 times speed

Fully Automatic Laser Power Control (ALPC) including
stabilization plus a separate laser supply voltage for
power efficiency

Adjustable current range of ALPC output

Automatic N- or P-substrate monitor diode selection

Adjustable laser bandwidth and laser switch-on current
slope using external capacitor

Protection circuit to prevent laser damage due to laser
supply voltage dip

Optimized interconnection between data amplifier and
Philips' digital signal processor CD10 (SAA7324)

Wide supply voltage range

Power-down switch to reduce power consumption
during standby

Low power consumption.

GENERAL DESCRIPTION

The TZA1024 is a data amplifier and laser supply circuit for
voltage output mechanisms found in a wide range of audio
and video CD systems. The device contains an RF
amplifier and an automatic laser power control circuit.

The preamplifier forms a versatile, programmable
interface for voltage output CD mechanisms to the Philips'
digital signal processor CD10 (SAA7324).

The RF bandwidth allows this device to be used in CD-A/V
and CD-R/W applications with a data rate up to a
maximum of n = 4 times speed. The RF gain can be
adapted for CD-A/V discs or CD-R/W discs by means of
the gain select signal.

The equalizer can be adjusted for n = 1 or n = 2 times
speed with the equalizer/speed select signal. For n = 4
times speed the RF is not equalized.

The TZA1024 can be adapted to a wide range of voltage
output mechanisms by means of external resistors.

The ALPC circuit will maintain control over the laser diode
current. With an on-chip reference voltage generator, a
constant and stabilized output power is ensured
independent of ageing. The ALPC can accommodate
N- or P-substrate monitor diodes.

A separate supply voltage connection for the laser allows
the internal power dissipation to be reduced by connecting
a low voltage supply. The laser output current range can
be optimized to fit the requirements of the laser diode by
means of one external resistor. When a DC-to-DC
converter is used, in combination with the control loop of
the ALPC, the adjustable output current range provides
the possibility to compensate for the extra gain a DC-to-DC
converter introduces in the control loop.

1998 Oct 30

Philips Semiconductors

Product specification

Data amplifier and laser supply circuit for CD
audio and video optical systems (ADALAS)

TZA1024

QUICK REFERENCE DATA

ORDERING INFORMATION

SYMBOL

PARAMETER

CONDITIONS

MIN.

TYP.

MAX.

UNIT

Supplies

supply voltage

2.4

5.5

supply current

DD(L)

laser supply voltage

2.4

5.5

RF amplifier

d(f)(RF)

RF flatness delay

EQSEL = LOW; n = 1

EQSEL = HIGH; n = 2

EQSEL = open-circuit;
n = 4; non equalized

2.5

Laser supply circuit

o(LASER)(max)

maximum laser output current

DD(L)

o(LASER)

= 0.55 V 80

i(mon)

monitor input voltage

N-substrate monitor diode

0.150

P-substrate monitor diode

0.150

Temperature range

oper

operating temperature

TYPE

NUMBER

PACKAGE

NAME

DESCRIPTION

VERSION

TZA1024T

SO14

plastic small outline package; 14 leads; body width 3.9 mm

SOT108-1

1998 Oct 30

Philips Semiconductors

Product specification

Data amplifier and laser supply circuit for CD
audio and video optical systems (ADALAS)

TZA1024

PINNING

FUNCTIONAL DESCRIPTION

The TZA1024 consists of two sections, the RF amplifier
and the automatic laser power control circuit.

RF amplifier

The RF amplifier consists of a current input amplifier, an
equalizer/bandwidth section and a transimpedance output
amplifier with an external feedback resistor of 10 k

(fixed

value).

SYMBOL

PIN

DESCRIPTION

current output to laser diode

DD(L)

laser supply voltage

CFIL

external filter capacitor

MON

laser monitor diode input

DIN

central diode input

GND

ground

PWRON

power-on select input

CMFB

common mode feedback voltage
input

RFFB

external RF feedback resistor

RFEQO

RF amplifier output

CDRW

gain select input for CD-A/V, CD-R/W

EQSEL

equalizer/speed select input
(n = 1, 2 or 4)

supply voltage

RGADJ

external laser supply gain adjust
resistor

Fig.2 Pin configuration.

handbook, halfpage

MGR518

TZA1024

VDD(L)

CFIL

MON

DIN

GND

PWRON

CMFB

RFFB

RFEQO

CDRW

EQSEL

VDD

RGADJ

The gain of the RF amplifier can be adjusted by the
external input resistors. Fig.3 shows the simplified
schematic which can be used to determine the RF gain.
The signal is AC coupled to the RF amplifier. The formula
to determine the gain is shown below:

(1)

where:

is the RF amplifier gain

n is the number of input resistors

tr(RF)

is the transimpedance of the amplifier (

)

R2 is the value of the input resistors (

The gain can be increased by a factor 4 by making
pin CDRW HIGH. The value of Z

tr(RF)

is 9.8 k

for CD-A/V

(CDRW = LOW) and 38 k

for CD-R/W (CDRW = HIGH).

The equalizer/bandwidth section can be switched between
n = 1, n = 2 (inclusive the corresponding equalizer) or
n = 4 (inclusive the required bandwidth limitation) times
speed.

The DC output level of the amplifier can be set by applying
a DC voltage on the common mode feedback pin CMFB.
Since the input signal is AC-coupled the RF output voltage
will swing (symmetrically) around this DC level.

The coupling of the TZA1024 to the signal processor
(SAA7324) can be either AC or DC. When an AC-coupling
is chosen (see Fig.8) the minimum supply voltage can be
applied. When a DC-coupling is chosen (see Fig.9) a
minimum supply voltage of 2.8 V is required.

tr RF

(

)

------------------

Fig.3 Simplified schematic.

handbook, halfpage

CDRW

RFEQO

10 k

Vin

R2(1)

R2(2)

R2(n)

Vin

MGL530

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