TZA1026 Datasheet, PDF (5/20 Pages) NXP Semiconductors – Data amplifier and laser supply circuit for CD audio and video optical systems ADALASAuto

Philips Semiconductors
Data amplifier and laser supply circuit for CD
audio and video optical systems (ADALASAuto)
Product specification
TZA1026
PINNING
SYMBOL PIN
DESCRIPTION
LD
1 current output to laser diode
V_DD(L)
CFIL
2 laser supply voltage
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
RGADJ
13 supply voltage
14 external laser supply gain adjust
resistor
handbook, halfpage
LD 1
VDD(L) 2
CFIL 3
MON 4
DIN 5
GND 6
PWRON 7
14 RGADJ
13 VDD
12 EQSEL
TZA1026 ¹¹ CDRW
10 RFEQO
9 RFFB
8 CMFB
MBK890
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 = –n × ^Z----t--R^r---⁽--^R_2---^F---⁾-
(1)
where:
G_RF is the RF amplifier gain
n is the number of input resistors
Z_tr(RF) is the transimpedance of the amplifier (Ω)
R2 is the value of the input resistors(Ω).
The gain can be increased by a factor 4 by making
pin CDRW HIGH. The value of Z_tr(RF) is 9.8 kΩ for CD-A/V
(CDRW = LOW) and 38 kΩ 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 TZA1026 to the signal processor
(SAA7326) 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.
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 kΩ (fixed
value).
handbook, halfpage
Vin
Vin
Vin
R2(1)
R2(2) _C2
10 kΩ
R2(n)
CDRW
RFEQO
MGL530
Fig.3 Simplified schematic.
1998 Oct 30
5