tza3031ahl NXP Semiconductors, tza3031ahl Datasheet - Page 15

• Manufacturer Part Number: tza3031ahl
• Description: Sdh/sonet Stm1/oc3 Laser Drivers
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Loop mode for TZA3031BHL
The loop mode allows the total system application to be
tested. It allows for uninhibited optical transmission
through the fibre front-end (from the MPD through the
transimpedance stage and the data and clock recovery
unit, to the laser driver and via the laser back to the fibre).
Note that the optical receiver used in conjunction with the
TZA3031BHL must have a loop mode output in order to
complete the test loop.
The loop mode is selected by a HIGH level on pin ENL.
By default, pin ENL is pulled to a LOW level by a 25 k
pull-down resistor (see Fig.16).
Power supply connections
Refer to application diagrams Figs 18 and 19. Three
separate supply domains (labelled V
V
the high-current outputs, and the PECL or CML inputs.
Each supply domain should be connected to a central V
via separate filters as shown in Figs 18 and 19. All supply
pins must be connected. The voltage supply levels
should be equal to, and in accordance with, the values
specified in Chapter “Characteristics”.
2002 Aug 13
handbook, halfpage
CC(R)
SDH/SONET STM1/OC3 laser drivers
) provide isolation between the MPD current input,
ENL
600
Fig.16 ENL input.
GND
25 k
MGS912
CC(G)
V CC(R)
, V
CC(B)
, and
CC
15
To maximize power supply isolation, the cathode of the
MPD should be connected to V
laser diode should be connected to V
recommended that the laser diode anode is also
connected to a separate decoupling capacitor C9.
Generally, the inverted laser modulation output (pin LAQ)
is not used. To correctly balance the output stage, an
equalization network (Z1) with an impedance comparable
to the laser diode is connected between pin LAQ and
V
All external components should be surface mounted
devices, preferably of size 0603 or smaller.
The components must be mounted as close to the IC as
possible.
It is especially recommended to mount the following
components very close to the IC:
Bare die ground
In addition to the separate V
contains three corresponding ground (GND) domains.
Isolation between the GND domains is limited due to the
finite substrate conductance.
Mount the die preferably on a large and highly conductive
grounded die pad. All GND pads must be bonded to the
die pad. The external ground is thus ideally combined with
the die ground to avoid ground bounce problems.
Layout recommendations
Layout recommendations for the TZA3031AHL and
TZA3031BHL can be found in application note “AN98090
Fiber optic transceiverboard STM1/4/8, OC3,12,24,
FC/GE” .
CC(B)
Power supply decoupling capacitors C2, C3 and C4
Input matching network on pins DIN, DINQ, DLOOP and
DLOOPQ
Capacitor C5 on pin MONIN
Output matching network Z1 at the unused output
The laser.
.
TZA3031AHL; TZA3031BHL;
CC
CC(G)
domains, the bare die
and the anode of the
Product specification
CC(B)
TZA3031U
. It is