Philips TZA1024T-V2, TZA1024T-N1 Datasheet

DATA SH EET
Product specification File under Integrated Circuits, IC01
1998 Oct 30
INTEGRATED CIRCUITS
TZA1024
Data amplifier and laser supply circuit for CD audio and video optical systems (ADALAS)
1998 Oct 30 2
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 3
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
V
DD
supply voltage 2.4 5.5 V
I
DD
supply current 3 mA
V
DD(L)
laser supply voltage 2.4 5.5 V
RF amplifier
t
d(f)(RF)
RF flatness delay EQSEL = LOW; n = 1 −− 10 ns
EQSEL = HIGH; n = 2 −− 5ns EQSEL = open-circuit;
n = 4; non equalized
−− 2.5 ns
Laser supply circuit
I
o(LASER)(max)
maximum laser output current V
DD(L)
V
o(LASER)
= 0.55 V 80 −−mA
V
i(mon)
monitor input voltage
N-substrate monitor diode 0.150 V P-substrate monitor diode V
DD
0.150 V
Temperature range
T
oper
operating temperature 0 70 °C
TYPE
NUMBER
PACKAGE
NAME DESCRIPTION VERSION
TZA1024T SO14 plastic small outline package; 14 leads; body width 3.9 mm SOT108-1
1998 Oct 30 4
Philips Semiconductors Product specification
Data amplifier and laser supply circuit for CD audio and video optical systems (ADALAS)
TZA1024
BLOCK DIAGRAM
Fig.1 Block diagram.
(1) Band gap reference voltage.
handbook, full pagewidth
MGR517
250 kHz
8
4×
2×
1×
TZA1024
14
3 7
10
1
12
9
V/I
V/I
V
DD(L)
V
DD
V
DD
GND
26
V
GAP
MON
4
(1)
DIN
5
CDRW
11
V
DD
13
LD
CFIL
PWRON
RGADJ
CMFB
RFFB
RFEQO
EQSEL
1998 Oct 30 5
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
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
Fig.2 Pin configuration.
handbook, halfpage
MGR518
TZA1024
1 2 3 4 5 6 7
8
14 13 12 11 10
9
LD
V
DD(L)
CFIL
MON
DIN
GND
PWRON
CMFB
RFFB
RFEQO
CDRW
EQSEL
V
DD
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:
GRF is the RF amplifier gain n is the number of input resistors Z
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.
G
RF
n
Z
tr RF()
R2
------------------
×=
Fig.3 Simplified schematic.
handbook, halfpage
CDRW
RFEQO
C2
10 k
V
in
R2(1) R2(2)
R2(n)
V
in
V
in
MGL530
1998 Oct 30 6
Philips Semiconductors Product specification
Data amplifier and laser supply circuit for CD audio and video optical systems (ADALAS)
TZA1024
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:
(2)
where:
G
loop
is the loop gain
G
ALPC
is the ALPC transfer (60 A/V) Glm is the laser-to-monitor transfer (V/A) G
con
is the extra gain introduced when a DC-to-DC
converter is used in the loop; G
con
= 1 when no
DC-to-DC converter is used 250 is a fixed internal resistor value () R
RGADJ
is the value of the external resistor ().
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).
(3)
G
loop
G
ALPCGlm
× G
con
×
250
250 R
RGADJ
+
-------------------------------------
×=
I
oIo(LASER)(max)
250
250 R
RGADJ
+
-------------------------------------
×=
where:
I
o
is output current (mA)
I
o(LASER)(max)
is the maximum laser output current (mA) 250 is a fixed internal resistor value () R
RGADJ
is the value of the external resistor ().
The bandwidth of the loop is determined by the external filter capacitor C
CFIL
and the loop gain. The formula to
determine the bandwidth is shown in equation (4).
(4)
where:
C
CFIL
is the value of the capacitor (F)
G
loop
is the loop gain.
The TZA1024 has a protection circuit to prevent laser damage that can occur due to a dip of V
DD(L)
. When a dip 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
CFIL
. After the dip a fully charged capacitor 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 has passed.
τ
-3dB
C
CFIL
16 106⋅×
G
loop
----------------------------------------- -
=
Fig.4 Automatic Laser Power Control (ALPC) loop.
a. N-substrate monitor diode. b. P-substrate monitor diode.
handbook, full pagewidth
MGR519
DC-TO-DC
CONVERTER
C
CFIL
C
CFIL
V
DD(L)
150 mV
DC-TO-DC
CONVERTER
V
DD(L)
V
DD
VDD 150 mV
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