oq2545hp NXP Semiconductors, oq2545hp Datasheet - Page 12

• Manufacturer Part Number: oq2545hp
• Description: Sdh/sonet Stm16/oc48 Laser Drivers
• Manufacturer: NXP Semiconductors

Philips Semiconductors
The current I
high RF resistance and a low DC resistance (e.g. 5 ).
When the laser is in the high (emitting) state, the voltage
drop across the diode and the modulation current of 40 mA
in combination with the bias current of 20 mA through the
30
V
No current through the 30
When the laser is in the low (dark) state, the bias current
of 20 mA results in V
The modulation current of 40 mA through the 30
sets the value V
The RF choke causes V
the average value of V
across the choke (bias current of 20 mA through 5 ):
V
Table 1 Estimate total power consumption
Note
1. 153 mA = I
1999 Aug 24
handbook, full pagewidth
P
P
P
P
P
P
P
LA
IBIAS
VEE1
VCC
VEE2
LA
LAQ
IBIAS
tot
SDH/SONET STM16/OC48 laser drivers
= 1.2
laser resistance results in:
= 0.5
70 mA
2 mA
153 mA
0.5
0.5
20 mA
P
VEE1
(P
BIAS
30
LA
( 3.0
40 mA
40 mA
EE2
+ P
LAQ
+ P
5 V
(1)
is supplied through an RF choke with a
(0.040 + 0.020) = 3.0 V
4.5 V
(55 + 1.5
2.5 V
VCC
LAQ
= 30
LA
1.8)
6.5 V
LA
+ P
= 1.2
+ P
IBIAS
3.0 V
1.2 V
minus the small voltage drop
VEE2
0.040 = 1.2 V
IBIAS
0.020
resistor gives V
to be stationary and equal to
52 + 20 + 3
)
30
5 = 2.5 V
0.020 = 1.8 V
OQ2545
100
Fig.8 Laser high ‘light emitting’.
LAQ
0 + 55
1186 mW
I LA(int)
100
= 0 V.
315 mW
995 mW
10 mW
60 mW
24 mW
50 mW
resistor
V EE2
I mod
0).
12
I bias
Thermal requirements and cooling
The maximum allowed junction temperature for normal
operation is 125 C. With an application specific estimated
power dissipation and the maximum ambient temperature,
the required thermal resistance from junction to ambient
R
PCB layout for the IC. It is highly recommended to use
copper area fills around the 8 corner leads (pins V
the IC. If a single copper layer PCB with a copper
thickness of 0.034 mm is used, square copper area fills of
10
approximate value for R
originates from model calculations and is for indication
only. Lower values for R
multilayer PCBs.
If the required power dissipation is not known, but the
maximum ambient temperature is fixed, the maximum
allowed dissipation as a function of R
namely:
The maximum allowed dissipation to prevent overheating
as a function of the thermal resistance that is achieved in
the application is shown in Fig.12.
The maximum ambient temperature in this application is
85 C (i.e. 125
low R
th(j-a)
IBIAS
GND
LA
LAQ
MGL736
I LA(ext)
10 mm around the corner leads will result in an
th(j-a)
can be derived. This value strongly depends on the
30
P
EMI choke
tot
is recommended.
=
1.2 V
30
OQ2545HP; OQ2545BHP
125 T
----------------------------------------- -
85 = 40 C temperature head room). A
R
–
laser
I BIAS
th j a
th(j-a)
amb max
th(j-a)
–
= 35 K/W. This value
can be obtained with
Product specification
th(j-a)
can be derived,
EE2
) of