TZA1026T

Manufacturer Part NumberTZA1026T
DescriptionData amplifier and laser supply circuit for CD audio and video optical systems ADALASAuto
ManufacturerPhilips Semiconductors
TZA1026T datasheet
 
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Philips Semiconductors
Data amplifier and laser supply circuit for CD
audio and video optical systems (ADALASAuto)
PINNING
SYMBOL
PIN
DESCRIPTION
LD
1
current output to laser diode
V
2
laser supply voltage
DD(L)
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
13
supply voltage
DD
RGADJ
14
external laser supply gain adjust
resistor
handbook, halfpage
LD
1
V DD(L)
2
CFIL
3
MON
4
TZA1026
DIN
5
6
GND
PWRON
7
MBK890
Fig.2 Pin configuration.
FUNCTIONAL DESCRIPTION
The TZA1026 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
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
=
RF
where:
G
RF
n is the number of input resistors
Z
tr(RF)
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
(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.
14
RGADJ
The coupling of the TZA1026 to the signal processor
(SAA7326) can be either AC or DC. When an AC-coupling
V DD
13
is chosen (see Fig.8) the minimum supply voltage can be
12
EQSEL
applied. When a DC-coupling is chosen (see Fig.9) a
minimum supply voltage of 2.8 V is required.
11
CDRW
10
RFEQO
9
RFFB
8
CMFB
handbook, halfpage
5
Product specification
Z
tr RF
n
------------------
R2
is the RF amplifier gain
is the transimpedance of the amplifier ( )
is 9.8 k for CD-A/V
tr(RF)
10 k
R2(1)
V in
R2(2)
V in
C2
R2(n)
V in
CDRW
Fig.3 Simplified schematic.
TZA1026
(1)
RFEQO
MGL530