Philips tza1024 DATASHEETS

INTEGRATED CIRCUITS
DATA SH EET
TZA1024
Data amplifier and laser supply circuit for CD audio and video optical systems (ADALAS)
Product specification File under Integrated Circuits, IC01
1998 Oct 30
Philips Semiconductors Product specification
Data amplifier and laser supply circuit for CD audio and video optical systems (ADALAS)

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.
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.
TZA1024

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).
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 2
Philips Semiconductors Product specification
Data amplifier and laser supply circuit for CD
TZA1024
audio and video optical systems (ADALAS)

QUICK REFERENCE DATA

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT
Supplies
V
DD
I
DD
V
DD(L)
RF amplifier
t
d(f)(RF)
Laser supply circuit
I
o(LASER)(max)
V
i(mon)
Temperature range
T
oper
supply voltage 2.4 5.5 V supply current 3 mA laser supply voltage 2.4 5.5 V
RF flatness delay EQSEL = LOW; n = 1 −− 10 ns
EQSEL = HIGH; n = 2 −− 5ns EQSEL = open-circuit;
−− 2.5 ns
n = 4; non equalized
maximum laser output current V
DD(L)
V
o(LASER)
= 0.55 V 80 −−mA
monitor input voltage
N-substrate monitor diode 0.150 V P-substrate monitor diode V
0.150 V
DD
operating temperature 0 70 °C

ORDERING INFORMATION

TYPE
NUMBER
NAME DESCRIPTION VERSION
PACKAGE
TZA1024T SO14 plastic small outline package; 14 leads; body width 3.9 mm SOT108-1
1998 Oct 30 3
Philips Semiconductors Product specification
Data amplifier and laser supply circuit for CD audio and video optical systems (ADALAS)

BLOCK DIAGRAM

handbook, full pagewidth
CDRW
DIN
11
5
V
DD
13
1×
4×
TZA1024
V
DD
12
EQSEL
9
RFFB
10
RFEQO
MON
2×
250
TZA1024
V/I
4
GND
V
GAP
(1)
V/I
26
V
DD(L)
kHz
V
DD
14
MGR517
8
CMFB
1
LD
RGADJ
3
CFIL
7
PWRON
(1) Band gap reference voltage.
Fig.1 Block diagram.
1998 Oct 30 4
Philips Semiconductors Product specification
Data amplifier and laser supply circuit for CD audio and video optical systems (ADALAS)

PINNING

SYMBOL PIN DESCRIPTION
LD 1 current output to laser diode V
DD(L)
2 laser supply voltage CFIL 3 external filter capacitor MON 4 laser monitor diode input DIN 5 central diode input GND 6 ground PWRON 7 power-on select input CMFB 8 common mode feedback voltage
input RFFB 9 external RF feedback resistor RFEQO 10 RF amplifier output CDRW 11 gain select input for CD-A/V, CD-R/W EQSEL 12 equalizer/speed select input
(n = 1, 2 or 4) V
DD
13 supply voltage
RGADJ 14 external laser supply gain adjust
resistor
handbook, halfpage
LD
V
DD(L)
CFIL
MON
DIN
GND
PWRON
1 2 3 4 5 6 7
TZA1024
MGR518
14 13 12 11 10
9 8
RGADJ V
DD
EQSEL CDRW RFEQO RFFB CMFB
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:
G
where:
The gain can be increased by a factor 4 by making pin CDRW HIGH. The value of Z (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.
Z
tr RF()
n
×=
RF
-----------------­R2
GRF is the RF amplifier gain n is the number of input resistors Z
is the transimpedance of the amplifier ()
tr(RF)
R2 is the value of the input resistors ().
is 9.8 k for CD-A/V
tr(RF)
TZA1024
(1)
Fig.2 Pin configuration.

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).
1998 Oct 30 5
handbook, halfpage
V
in
V
in
V
in
R2(1) R2(2)
R2(n)
10 k
C2
CDRW
Fig.3 Simplified schematic.
RFEQO
MGL530
Philips Semiconductors Product specification
Data amplifier and laser supply circuit for CD audio and video optical systems (ADALAS)

Automatic laser power control circuit

The ALPC stabilises the laser output power thereby reducing the effect of ageing of the laser.
The TZA1024 automatically detects when an N- or P-substrate monitor diode is used and selects the correct reference voltage. A simplified diagram for the use of an N- or P-substrate monitor diode is given in Fig.4.
The gain of the loop can be controlled (reduced) by adding an external resistor between pins RGADJ and GND. The loop gain then becomes:
G
loop
G
× G
ALPCGlm
×
con
250
×=
------------------------------------­250 R
+
RGADJ
where:
G
is the loop gain
loop
G
is the ALPC transfer (60 A/V)
ALPC
Glm is the laser-to-monitor transfer (V/A) G
is the extra gain introduced when a DC-to-DC
con
converter is used in the loop; G
= 1 when no
con
DC-to-DC converter is used 250 is a fixed internal resistor value () R
is the value of the external resistor ().
RGADJ
The minimum available output current is also reduced when an external resistor is used. The formula to determine the minimum available output current is shown in equation (3).
I
oIo(LASER)(max)
250
×=
------------------------------------­250 R
+
RGADJ
where:
The bandwidth of the loop is determined by the external filter capacitor C determine the bandwidth is shown in equation (4).
τ
-3dB
(2)
where:
The TZA1024 has a protection circuit to prevent laser damage that can occur due to a dip of V occurs the output transistor (see Fig.4) will go into saturation making it unable to supply the required laser current. Without the protection circuit the ALPC would still try to supply the required laser current by charging the filter capacitor C would create a large output current during the few milliseconds it needs to discharge the capacitor to a normal level. The protection circuit monitors the output transistor and switches off the ALPC when saturation occurs by discharging the capacitor. The ALPC will automatically restart within a few milliseconds after the dip
(3)
has passed.
is output current (mA)
I
o
I
o(LASER)(max)
is the maximum laser output current (mA)
250 is a fixed internal resistor value () R
C G
is the value of the external resistor ().
RGADJ
and the loop gain. The formula to
CFIL
C
=
----------------------------------------- -
is the value of the capacitor (F)
CFIL
is the loop gain.
loop
16 106⋅×
CFIL
G
loop
. After the dip a fully charged capacitor
CFIL
TZA1024
. When a dip
DD(L)
(4)
handbook, full pagewidth
150 mV
V
DD(L)
C
CFIL
DC-TO-DC
CONVERTER
a. N-substrate monitor diode. b. P-substrate monitor diode.
Fig.4 Automatic Laser Power Control (ALPC) loop.
1998 Oct 30 6
VDD 150 mV
V
DD(L)
C
CFIL
DC-TO-DC
CONVERTER
V
DD
MGR519
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