OQ2545BHP Philips Semiconductors, OQ2545BHP Datasheet - Page 11

• Manufacturer Part Number: OQ2545BHP
• Description: SDH/SONET STM16/OC48 laser drivers
• Manufacturer: Philips Semiconductors

Philips Semiconductors
RF connections
A coupled stripline or microstrip with an odd mode
characteristic impedance of 50
be used for the differential RF connections on the PCB.
This applies to the CML differential line pairs on pins CIN
and CINQ, DIN and DINQ, CLOOP and CLOOPQ,
DLOOP and DLOOPQ, and MON and MONQ.
In addition, the following lines should not differ in length by
more than 10 mm:
ESD protection
In order to achieve high frequency performance, it has
been necessary to make adjustments to the standard ESD
protection scheme. Inputs on pins DIN, DINQ, CIN, CINQ,
DLOOP, DLOOPQ, CLOOP and CLOOPQ and outputs on
pins MON and MONQ are protected by a reduced ESD
structure. The outputs on pins LA and LAQ have no
protection against ESD, so extra care should be taken
with these pins.
Power consumption
The total power consumption of the OQ2545(B)HP
depends strongly on the application. A rough guideline is
given to estimate the power consumption for a specific
application.
The total power dissipation (P
terms:
P
where
1. P
2. P
1999 Aug 24
tot
Lines to pins DIN, DINQ, CIN and CINQ
Lines to pins CLOOP, CLOOPQ, DLOOP
and DLOOPQ.
SDH/SONET STM16/OC48 laser drivers
= P
terms corresponding with the supplies V
required for the digital section and the TTL interfaces.
These 2 terms are application independent and only
depend on the process spread and supply voltages.
Values can be found in Chapter “Characteristics”.
consumption of the analog section, including the
modulation current and bias current. It is mainly
determined by the magnitude of the modulation
current and bias current and the additional biasing
currents of the preamplifier and emitter followers.
The supply current is the summation:
I
+ 55
EE2
VEE1
VEE2
VEE1
= 55 mA + 1.5
and P
= I
I
EFADJ
+ P
EE2
VCC
VCC
V
+ P
represent the power consumption
EE2
VEE2
I
mod
represents the power
+ I
tot
(P
) consists of the following
IBIAS
LA
(nominal value) should
+ P
+ 3
LAQ
+ P
I
AMPADJ
EE1
IBIAS
and V
)
CC
,
11
3. P
Example
Consider the following example to illustrate the calculation
of P
3 mW (optical high), i.e. an extinction ratio of 10 dB.
For this laser type this requires I
I
The series resistance of the laser is 30 . Therefore the
ratio is:
Consequently, a total I
be generated by the IC.
The impedance connected to pin LAQ is 30
As a result also I
(see Fig.9).
In first instance the eye pattern is of adequate quality and
the preamplifier and emitter follower do not need additional
bias current, i.e. pins AMPADJ and EFADJ can be left
open-circuit.
LA(ext)
where I
pins AMPADJ and EFADJ, respectively.
These figures are valid for nominal supply voltage and
temperature and are given for rough indication only.
external load (laser or EAM), caused by the
modulation and bias current. The expressions are:
P
P
P
The factor 0.5 represents the fact that, for a
(scrambled) random data pattern, the modulation
switch will be switched to either side 50% of the time
integrated over many cycles.
V
when the modulation current flows through pins LA
and LAQ, respectively and the values depend on the
external laser or EAM supply voltage, the forward
diode voltage drop and additional loads.
To increase the dissipation in the external load and
thereby decreasing the dissipation in the IC, the values
of V
additional external resistors. A minimum value of V
and V
A similar argument is valid for power consumption due
to the bias current. It should be noted that this is
important, because it provides an easy way to lower
the power dissipation of the IC.
tot
LA
LA
LAQ
IBIAS
LA
. A laser diode operates at 0.3 mW (optical low) and
= 40 mA (see Fig.8).
, P
= 0.5
and V
----------------- -
I
I
LA
LA ext
= 0.5
LA int
LAQ
LAQ
= I
AMPADJ
or V
IBIAS
is required for proper operation of the IC.
LAQ
and P
I
OQ2545HP; OQ2545BHP
LA(ext)
=
LAQ(ext)
I
LAQ(ext)
are the voltages on pins LA and LAQ
LAQ
and I
--------- -
100
30
IBIAS
V
IBIAS
mod
can be increased by adding
EFADJ
= 40 mA and I
represent the dissipation in the
V
= (130/100)
LA
.
V
LAQ
are the currents through
,
BIAS
and
= 20 mA and
Product specification
LAQ(int)
40 = 52 mA will
= 12 mA
as well.
LA