TZA3001BHL Philips Semiconductors, TZA3001BHL Datasheet - Page 6

• Manufacturer Part Number: TZA3001BHL
• Description: SDH/SONET STM4/OC12 laser drivers
• Manufacturer: Philips Semiconductors

Philips Semiconductors
FUNCTIONAL DESCRIPTION
The TZA3001AHL, TZA3001BHL and TZA3001U laser
drivers accept a 622 Mbits/s STM4 Non-Return to Zero
(NRZ) input data stream and generate an output signal
with sufficient current to drive a solid state Fabry Perot
(FP) or Distributed FeedBack (DFB) laser. They also
contain dual loop control circuitry for stabilizing the true
laser optical power levels representing logic 1 and logic 0.
The input buffers present a high impedance to the data
stream on the differential inputs (pins DIN and DINQ).
The input signal can be at CML level of approximately
200 mV (p-p) below the supply voltage, or at PECL level
up to 800 mV (p-p). The inputs can be configured to accept
CML signals by connecting external 50
between pins DIN and DINQ to V
compatibility is required, the usual Thevenin termination
can be applied.
For ECL signals (negative and referenced to ground) the
inputs should be AC-coupled to the signal source.
If AC-coupling is applied, a constant input signal (either
low of high) will bring the device in an undefined state.
To avoid this, it is recommended to apply a slight offset to
the input stage. The applied offset must be higher than the
specified value in Chapter “Characteristics”, but much
lower than the applied input voltage swing.
1999 Aug 24
handbook, full pagewidth
SDH/SONET STM4/OC12 laser drivers
V CC(G)
MONIN
TZERO
TONE
BGAP
GND
GND
GND
CC(R)
1
2
3
4
5
6
7
8
. If PECL
Fig.4 Pin configuration of TZA3001BHL.
pull-up resistors
TZA3001BHL
6
The RF path is fully differential and contains a differential
preamplifier and a main amplifier. The main amplifier is
designed to handle large peak currents required at the
output laser driving stage and is insensitive to supply
voltage variations. The output signal from the main
amplifier drives a current switch which supplies a
guaranteed maximum modulation current of 60 mA at
pins LA and LAQ. Pin BIAS delivers a guaranteed
maximum DC bias current of up to 90 mA for adjusting the
optical laser output to a level above its light emitting
threshold.
Automatic laser control
A laser with a Monitor PhotoDiode (MPD) is required for
the laser control circuit (see Figs 6 and 7).
The MPD current is proportional to the laser emission and
is applied to pin MONIN. The MPD current range is from
100 to 1000 A (p-p). The input buffer is optimized to cope
with MPD capacitances up to 50 pF. To prevent the input
buffer breaking into oscillation with a low MPD
capacitance, it is required to increase the capacitance to
the minimum value specified in Chapter “Characteristics”
by connecting an extra capacitor between pin MONIN and
V
CC(G)
.
TZA3001AHL; TZA3001BHL;
19
18
17
MGK272
24
23
22
21
20
GND
ZERO
ONE
V CC(R)
DLOOPQ
DLOOP
V CC(R)
GND
Preliminary specification
TZA3001U