Philips oq2545hp, oq 2545bhp DATASHEETS

INTEGRATED CIRCUITS

DATA SH EET

OQ2545HP; OQ2545BHP

SDH/SONET STM16/OC48
laser drivers

Product specification
Supersedes data of 1997 Nov 27
File under Integrated Circuits, IC19

1999 Aug 24

Philips Semiconductors Product specification

SDH/SONET STM16/OC48 laser drivers OQ2545HP; OQ2545BHP

FEATURES

• Differential 50 Ω inputs for direct connection to
Current-Mode Logic (CML) outputs

• Internal retiming to minimize jitter (OQ2545HP only)

• Input clock phase margin of 320° at 2.5 Gbits/s

(OQ2545HP only)

• RF output current sinking capability of 60 mA

• Bias output current sinking capability of 100 mA

• TTL compatible control inputs

• Loop mode for system testing

• Continuous output monitoring

• Power dissipation <1500 mW (for typical application)

• Low cost LQFP48 plastic package.

APPLICATIONS

• Digital fibre optical modulation driver in STM16/OC48
short, medium and long haul optical transmission
systems

• Optical modulation driver in high-speed data networks

• High current driver for electro-optical converters

• High current electrical line driver.

GENERAL DESCRIPTION

The OQ2545 is a driver IC intended to be used with a
directly modulated laser diode or with an Electro
Absorption Modulator (EAM) in SDH/SONET 2.5 Gbits/s
optical transmission systems.

The IC features differentialdata inputs. Loop mode inputs
are provided for system testing, along with an output for
continuous monitoring. In addition, the OQ2545HP
features differential clock inputs for internal retiming
resulting in a better jitter performance.

The IChas bias and modulating currentoutputs, the levels
of which can be set separately. As an additional safety
measure, the active HIGH-level input for automatic laser
shutdown (pin ALS) can be used to switch off the laser
modulation and bias currents.

Although the IC is intended for 2.5 Gbits/s optical
transmission systems, it can be used in any application
requiring high current drive at high frequencies.

The IC is transparent from input to output.

ORDERING INFORMATION

TYPE

NUMBER

OQ2545HP
OQ2545BHP

NAME DESCRIPTION VERSION

LQFP48 plastic low profile quad flat package; 48 leads; body 7 × 7 × 1.4 mm SOT313-2

PACKAGE

1999 Aug 24 2

Philips Semiconductors Product specification

SDH/SONET STM16/OC48 laser drivers OQ2545HP; OQ2545BHP

BLOCK DIAGRAMS

handbook, full pagewidth

DIOA

DINQ

DLOOP

DLOOPQ

CINQ

CLOOP

CLOOPQ

DIN

CIN

3

33
34

22
21

30
31

28
27

BAND GAP

REFERENCE

BGCAP

DIGITAL SECTION

4543 17

ENL SMOD V

ANALOG SECTION

MONITOR

BUFFER

OQ2545HP

FF

42 16 15 44

EE1

PRE-

AMPLIFIER

EMITTER

FOLLOWERS

AMPADJ EFADJ ALS

MODULATION

DRIVER

(1)

8

V

EE2

GND

40

MON

39

MONQ

10

IBIAS

19

SIBIAS

5, 6
7, 8

(2)

46

14

V

CC

LA
LAQ

18

SIMOD

MGK368

(1) Pins 1, 12, 13, 24, 25, 36, 37 and 48.
(2) Pins 2, 4, 9, 11, 14, 20, 23, 26, 29, 32, 35, 38, 41 and 47.

Fig.1 Block diagram of OQ2545HP.

1999 Aug 24 3

Philips Semiconductors Product specification

SDH/SONET STM16/OC48 laser drivers OQ2545HP; OQ2545BHP

handbook, full pagewidth

DIOA

DINQ

DLOOP

DLOOPQ

DIN

i.c.
i.c.

i.c.
i.c.

3

33
34

22
21

30
31

28
27

BAND GAP

REFERENCE

BGCAP

DIGITAL SECTION

4543 17

ENL SMOD V

ANALOG SECTION

MONITOR

BUFFER

OQ2545BHP

FF

42 16 15 44

EE1

PRE-

AMPLIFIER

EMITTER

FOLLOWERS

AMPADJ EFADJ ALS

MODULATION

DRIVER

(1)

8

V

EE2

GND

40

MON

39

MONQ

10

IBIAS

19

SIBIAS

5, 6
7, 8

(2)

46

14

V

CC

LA
LAQ

18

SIMOD

MGL727

(1) Pins 1, 12, 13, 24, 25, 36, 37 and 48.
(2) Pins 2, 4, 9, 11, 14, 20, 23, 26, 29, 32, 35, 38, 41 and 47.

Fig.2 Block diagram of OQ2545BHP.

1999 Aug 24 4

Philips Semiconductors Product specification

SDH/SONET STM16/OC48 laser drivers OQ2545HP; OQ2545BHP

PINNING

SYMBOL

PIN

TYPE

(1)

DESCRIPTION

OQ2545HP OQ2545BHP

V

EE2

1 1 S supply voltage for analog section (−6.5 V)
GND 2 2 S ground supply
DIOA 3 3 A temperature sensing diode array connection
GND 4 4 S ground supply
LA 5 5 O laser modulation current output
LA 6 6 O laser modulation current output
LAQ 7 7 O inverted laser modulation current output
LAQ 8 8 O inverted laser modulation current output
GND 9 9 S ground supply
IBIAS 10 10 O laser bias current control output
GND 11 11 S ground supply
V

EE2

V

EE2

12 12 S supply voltage for analog section (−6.5 V)

13 13 S supply voltage for analog section (−6.5 V)
GND 14 14 S ground supply
EFADJ 15 15 AI input for emitter follower current adjustment
AMPADJ 16 16 AI input for preamplifier current adjustment
SMOD 17 17 I input for data polarity switch
SIMOD 18 18 I input for RF modulated output current control
SIBIAS 19 19 I input for DC output current control
GND 20 20 S ground supply
DLOOPQ 21 21 I inverted loop mode data input
DLOOP 22 22 I loop mode data input
GND 23 23 S ground supply
V

EE2

V

EE2

24 24 S supply voltage for analog section (−6.5 V)

25 25 S supply voltage for analog section (−6.5 V)
GND 26 26 S ground supply
CLOOPQ 27 − I inverted loop mode clock input
i.c. − 27 − internally connected; internal resistance of 50 Ω to GND
CLOOP 28 − I loop mode clock input
i.c. − 28 − internally connected; internal resistance of 50 Ω to GND
GND 29 29 S ground supply
CIN 30 − I clock input
i.c. − 30 − internally connected; internal resistance of 50 Ω to GND
CINQ 31 − I inverted clock input
i.c. − 31 − internally connected; internal resistance of 50 Ω to GND
GND 32 32 S ground supply
DIN 33 33 I data input
DINQ 34 34 I inverted data input

1999 Aug 24 5

Philips Semiconductors Product specification

SDH/SONET STM16/OC48 laser drivers OQ2545HP; OQ2545BHP

SYMBOL

PIN

TYPE

(1)

DESCRIPTION

OQ2545HP OQ2545BHP

GND 35 35 S ground supply
V

EE2

V

EE2

36 36 S supply voltage for analog section (−6.5 V)

37 37 S supply voltage for analog section (−6.5 V)
GND 38 38 S ground supply
MONQ 39 39 O inverted monitor data output
MON 40 40 O monitor data output
GND 41 41 S ground supply
V

EE1

42 42 S supply voltage for digital section (−4.5 V)
BGCAP 43 43 A connection for band gap reference decoupling capacitor
ALS 44 44 I automatic laser shutdown control input
ENL 45 45 I loop mode enable input (active LOW)
V

CC

46 46 S positive supply voltage for TTL interface (+5 V)
GND 47 47 S ground supply
V

EE2

48 48 S supply voltage for analog section (−6.5 V)

Note

1. Pin type abbreviations: O = output, I = input, S = power supply and A = analog function.

handbook, full pagewidth

V

EE2

GND

DIOA

GND

LA

LA
LAQ
LAQ

GND

IBIAS

GND

V

EE2

CC

EE2

V

GND
47

14

GND

46

15

EFADJ

ENL

ALS

45

44

OQ2545HP

16

17

SMOD

AMPADJ

V
48

1
2
3
4
5
6
7
8

9
10
11
12

13

EE2

V

EE1

V

BGCAP
43

42

18

19

SIBIAS

SIMOD

GND
41

20

GND

MON

MONQ

40

39

21

22

DLOOP

DLOOPQ

GND
38

23

GND

EE2

V

24 37

EE2

V

36
35
34
33
32
31
30
29
28
27
26
25

MGK367

V

EE2

GND
DINQ
DIN
GND
CINQ
CIN
GND
CLOOP
CLOOPQ
GND
V

EE2

Fig.3 Pin configuration of OQ2545HP.

1999 Aug 24 6

Philips Semiconductors Product specification

SDH/SONET STM16/OC48 laser drivers OQ2545HP; OQ2545BHP

handbook, full pagewidth

V
48

EE2

GND
47

CC

V

ENL

ALS

46

45

44

EE1

V

BGCAP
43

42

GND
41

MON
40

MONQ
39

GND
38

EE2

V

V

EE2

GND

DIOA

GND

LA

LA
LAQ
LAQ

GND

IBIAS

GND

V

EE2

1
2
3
4
5
6
7
8

9
10
11
12

13

14

EE2

GND

V

15

EFADJ

16

AMPADJ

OQ2545BHP

17

18

19

SMOD

SIBIAS

SIMOD

Fig.4 Pin configuration of OQ2545BHP.

20

GND

21

22

DLOOP

DLOOPQ

23

GND

24 37

EE2

V

36
35
34
33
32
31
30
29
28
27
26
25

MGL728

V

EE2

GND
DINQ
DIN
GND
i.c.
i.c.
GND
i.c.
i.c.
GND
V

EE2

1999 Aug 24 7

Philips Semiconductors Product specification

SDH/SONET STM16/OC48 laser drivers OQ2545HP; OQ2545BHP

FUNCTIONAL DESCRIPTION

The OQ2545(B)HP can be divided into two functional
blocks (see Fig.1):

• A digital section on the input side

• An analog section on the output side.

The data input buffers present an impedance of 50 Ω to
the data stream on the differential data inputs (see Fig.5).
The input data is then fed to a multiplexer where normal
mode (pin ENL = HIGH-level) or loop mode
(pin ENL = LOW-level) inputs are selected. For driving an
EAM, a second multiplexer inverts the input signals when
pin SMOD is connected to V

EE1

.

An external clock (OQ2545HP only) connected to a
master-slave flip-flop is then used to retime the data. This
reduces jitter on the data signal to a minimum.

Thepreamplifierbooststhesignaltoasuitable level for the
modulation driver. Two emitter followers provide the
necessary signal isolation between the preamplifier and
the high current modulation driver. The bias currents for
thepreamplifierandtheemitterfollowerscontainanoutput
level dependent component, along with an independent
component. The output level dependent component is
controlledvia the signal on pin SIMODand the operational
amplifier, which also sets the modulation driver level.
The independent component is adjusted by means of the
signal on pin AMPADJ (preamplifier) and pin EFADJ
(emitter followers).

The signal on pin AMPADJ also controls the shape of the
output signal on pins LA and LAQ.

An independent adjustable on-chip bias current source is
provided to drive directly a modulated laser diode.
Pin SIBIAS is used to set the bias current level. Theoutput
current at pin IBIAS will be approximately 106 times the
input current at pin SIBIAS. A similar arrangement is used
to control the modulation current at pins LA and LAQ.
The output current at pins LA and LAQ is proportional to
the input current at pin SIMOD. The coefficient depends
on the load impedance on pins LA and LAQ and on the
voltage setting of pin SMOD (see section ‘Modulation
current setting’).

Pin ALS is a TTL compatibleinput and at HIGH-level itcan
be used to switch off all current sources. This function
makes it possible to implement safety measures that will
switch off the circuit in the event of an optical system
malfunction.

The buffered differential 50 Ω outputs (pins MON
and MONQ) can be used to monitor the optically
modulated data.

Loop mode

Theloopmodeisprovidedforsystemtesting.ALOW-level
on pin ENL selects the loop mode. When pin ENL is left
open-circuit, it is pulled to a HIGH-level (TTL) by an
internal pull-up resistor.

andbook, full pagewidth

DIN, DLOOP
CIN, CLOOP

V

EE1

Fig.5 Schematic for CML differential inputs.

1999 Aug 24 8

50 Ω50 Ω

MGL731

DINQ, DLOOPQ,
CINQ, CLOOPQ

Philips Semiconductors Product specification

SDH/SONET STM16/OC48 laser drivers OQ2545HP; OQ2545BHP

Automatic laser shutdown

A HIGH-level (TTL) on pin ALS switches off the laser
modulation and bias currents. This function allows the
circuit to be switched off in the event of an optical system
malfunction or for system maintenance. When not
connected, pin ALS is pulled to a LOW-level (TTL) by an
internal pull-down resistor.

Data monitoring

Pins MON and MONQ can be used as data monitor
outputs. They need to be AC-coupled, e.g. to a 50 Ω
matched RF amplifier with sufficient bandwidth.

Output polarity selection

Pin SMOD is used to set the correct logic assignment
between the data input on pins DIN and DINQ (or
pins DLOOP and DLOOPQ) and the data output on
pins LA, LAQ, MON and MONQ. This is necessary
because a directly modulated laser diode and an EAM
have different output voltage requirements.

Ifa laser diode is used and connected between pin LAand
ground, a high current through pin LA corresponds to a
logic HIGH, while a low current through pin LA
corresponds to a logic LOW.

The opposite is the case with an EAM, where a high
current (i.e. a large voltage across the load) activates the
EAM, thereby causing a logic LOW. Therefore, an
inversion is needed between input and output. This
happens in the second multiplexer when pin SMOD is
connected to V

. When left open-circuit, pin SMOD is

EE1

pulled-up to ground, which is the laser diode setting.

Modulation current setting

Pin SIMOD is used to adjust the modulation current on
pins LA and LAQ (see Fig.6). This is achieved by
regulating the internal current mirror, which serves as a
reference current for the modulation driver. The reference
port of the control operational amplifier is connected to
ground through an internal 4 kΩ resistor, thus establishing
a ‘virtual earth’ on pin SIMOD (DC level is 0 V).
An external (approximately) 4 kΩ resistor connected to an
adjustable voltage source is needed to regulate the
internal current mirror. This adjustable voltage source can
be a part of the laser current control box (see Fig.15).

Theratio between the current intopin SIMOD and the total
modulation current depends on the polarity setting via
pin SMOD. When pin SMOD=0V the value of
I

=92× I

mod

pin SMOD = V

(approximately) and whereas

SIMOD

the value of I

EE1

mod

= 107 × I

SIMOD

(approximately).

handbook, full pagewidth

4 kΩ 100 Ω 100 Ω

V

EE2

SIMOD

(1) k = 1.3 when pin SMOD = 0 V.

k = 1.5 when pin SMOD = V

EE1

I

SIMOD

.

Fig.6 Schematic of laser modulation outputs.

1999 Aug 24 9

k × I

+

SIMOD

−

71 × k × I

MGL733

LA

LAQ

SIMOD

(1)