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PDF TZA1025 Data sheet ( Hoja de datos )
| Número de pieza | TZA1025 | |
| Descripción | Data amplifier and laser supply circuit for CD audio and video optical systems ADALASLC | |
| Fabricantes | NXP Semiconductors | |
| Logotipo |  |
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INTEGRATED CIRCUITS
DATA SHEET
TZA1025
Data amplifier and laser supply
circuit for CD audio and video
optical systems (ADALASLC)
Product specification
File under Integrated Circuits, IC01
1998 Oct 30
1 page  
Philips Semiconductors
Data amplifier and laser supply circuit for CD
audio and video optical systems (ADALASLC)
Product specification
TZA1025
Automatic laser power control circuit
The ALPC stabilises the laser output power thereby
reducing the effect of ageing of the laser.
The TZA1025 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:
Gloop = GALPC × Glm × Gcon × 2----5---0-----+--2---R-5---0-R---G----A---D----J-
(2)
where:
Gloop is the loop gain
GALPC is the ALPC transfer (60 A/V)
Glm is the laser-to-monitor transfer (V/A)
Gcon is the extra gain introduced when a DC-to-DC
converter is used in the loop; Gcon = 1 when no
DC-to-DC converter is used
250 is a fixed internal resistor value (Ω)
RRGADJ is the value of the external resistor (Ω).
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).
Io = Io(LASER)(max) × 2----5---0-----+--2---R-5---0-R---G----A---D----J-
(3)
where:
Io is output current (mA)
Io(LASER)(max) is the maximum laser output current (mA)
250 is a fixed internal resistor value (Ω)
RRGADJ is the value of the external resistor (Ω).
The bandwidth of the loop is determined by the external
filter capacitor CCFIL and the loop gain. The formula to
determine the bandwidth is shown in equation (4).
τ-3dB = C-----C----F---I-L-G---×--l--o-1--o--6p----⋅---1----0---6-
(4)
where:
CCFIL is the value of the capacitor (F)
Gloop is the loop gain.
The TZA1025 has a protection circuit to prevent laser
damage that can occur due to a dip of VDD(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 CCFIL. 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.
handbook, full pagewidVtDh D(L)
150 mV
DC-TO-DC
CONVERTER
CCFIL
VDD(L)
VDD − 150 mV
DC-TO-DC
CONVERTER
CCFIL
VDD
a. N-substrate monitor diode.
MGR519
b. P-substrate monitor diode.
Fig.4 Automatic Laser Power Control (ALPC) loop.
1998 Oct 30
5
5 Page 
Philips Semiconductors
Data amplifier and laser supply circuit for CD
audio and video optical systems (ADALASLC)
Product specification
TZA1025
The application for the TZA1025 (ADALASLC) with the SAA7325 (CD10LC) without a coupling capacitor is shown in
Fig.7. A minimum supply voltage (VDD) is required for optimal performance.
handbook, full pagewidth
VDD(LASER)
VDD(5)
from
microprocessor(2)
LD
MON
VCOM
LD
1
100 nF
VDD(L)
2
10 nF CFIL
3
RGADJ RRGADJ(1)
14
VDD
13
GND
12
VDD
MON 4 (ATDZAAL1A0S2L5C)11 CDRW
DIN RFEQO
5 10
GND
6
PWRON
7
RFFB
9
CMFB
8
10 kΩ(3)
100 nF
1 kΩ
47 pF
HFIN
HFREF
OPU
C2(4)
100 nF
ISLICE
100 nF
LDON
VRIN
SAA7325
(CD10LC)
R2 (4×)
D1
D2
D3
D4
S1
S2
D1
D2
D3
D4
S1
S2
LF FILTER
6 × 220 pF
MBK904
(1) See equation (3) to calculate the value of this resistor.
(2) Pin CDRW can be controlled by the CD10LC or a microprocessor but can also be fixed or switched by any other means.
(3) The 10 kΩ feedback resistor between pins 9 and 10 is a fixed value.
(4) The high-pass filter (AC-coupling) is placed at the input of the preamplifier. The −3 dB point (f = 10 kHz) is at -R----2-----(---Ω-----)----4×-----C-----2----(---F----)-
(5) The minimum supply voltage (VDD) without using a coupling capacitor is 2.8 V.
Fig.7 Application diagram with SAA7325 (CD10LC) without coupling capacitor.
1998 Oct 30
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet TZA1025.PDF ] | |
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