Philips oq2545hp, oq 2545bhp DATASHEETS

INTEGRATED CIRCUITS

DATA SHEET

OQ2545HP; OQ2545BHP

SDH/SONET STM16/OC48 laser drivers

Product specification

1999 Aug 24

Supersedes data of 1997 Nov 27

File under Integrated Circuits, IC19

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.

ORDERING INFORMATION

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 differential data 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 IC has bias and modulating current outputs, 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.

	TYPE		PACKAGE
	NUMBER	NAME	DESCRIPTION	VERSION
	OQ2545HP	LQFP48	plastic low profile quad flat package; 48 leads; body 7 × 7 × 1.4 mm	SOT313-2
	OQ2545BHP

1999 Aug 24

2

Philips Semiconductors	Product specification
SDH/SONET STM16/OC48 laser drivers	OQ2545HP; OQ2545BHP
BLOCK DIAGRAMS

3	DIGITAL SECTION				ANALOG SECTION					40
DIOA											MON
										39
33											MONQ
DIN				MONITOR						10
34											IBIAS
DINQ				BUFFER
22										19
DLOOP				OQ2545HP							SIBIAS
21
DLOOPQ
30			FF	PRE-
				AMPLIFIER			MODULATION
CIN
31					EMITTER		DRIVER			5, 6	LA
CINQ										7, 8
28					FOLLOWERS						LAQ
CLOOP
27
CLOOPQ
										18	SIMOD
BAND GAP
REFERENCE
43	45	17	42	16	15	44	(1)	(2)	46		MGK368
BGCAP	ENL	SMOD	VEE1	AMPADJ	EFADJ	ALS	8	14
							VEE2		VCC
								GND

(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

3	DIGITAL SECTION				ANALOG SECTION					40
DIOA											MON
										39
33											MONQ
DIN				MONITOR						10
34											IBIAS
DINQ				BUFFER
22										19
DLOOP				OQ2545BHP							SIBIAS
21
DLOOPQ
30			FF	PRE-
				AMPLIFIER			MODULATION
i.c.							DRIVER
31					EMITTER					5, 6	LA
i.c.										7, 8
					FOLLOWERS						LAQ
28
i.c.
27
i.c.
										18	SIMOD
BAND GAP
REFERENCE
43	45	17	42	16	15	44	(1)	(2)	46		MGL727
BGCAP	ENL	SMOD	VEE1	AMPADJ	EFADJ	ALS	8	14
							VEE2		VCC
								GND

(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
VEE2	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
VEE2	12	12	S	supply voltage for analog section (−6.5 V)
VEE2	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
VEE2	24	24	S	supply voltage for analog section (−6.5 V)
VEE2	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
	VEE2		36	36	S	supply voltage for analog section (−6.5 V)
	VEE2		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
	VEE1		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
			45	45	I	loop mode enable input (active LOW)
	ENL
	VCC		46	46	S	positive supply voltage for TTL interface (+5 V)
	GND		47	47	S	ground supply
	VEE2		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

VEE2 1 GND 2

DIOA 3

GND 4

LA 5

LA 6

LAQ 7 LAQ 8

GND 9 IBIAS 10

GND 11

VEE2 12

V		GND		V		ENL		ALS		BGCAP		V		GND		MON		MONQ		GND		V
EE2				CC								EE1										EE2
48		47		46		45		44		43		42		41		40		39		38		37

OQ2545HP

13		14		15		16		17		18		19		20		21		22		23		24
EE2		GND		EFADJ		AMPADJ		SMOD		SIMOD		SIBIAS		GND		DLOOPQ		DLOOP		GND		EE2
V																						V

Fig.3 Pin configuration of OQ2545HP.

36 VEE2

35 GND

34 DINQ

33 DIN

32 GND

31 CINQ

30 CIN

29 GND

28 CLOOP

27 CLOOPQ

26 GND

25 VEE2

MGK367

1999 Aug 24

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Philips Semiconductors	Product specification
SDH/SONET STM16/OC48 laser drivers	OQ2545HP; OQ2545BHP

handbook, full pagewidth

	V	GND	V	ENL	ALS	BGCAP	V	GND	MON	MONQ	GND	V
	EE2		CC				EE1					EE2
	48	47	46	45	44	43	42	41	40	39	38	37
VEE2	1
GND	2
DIOA	3
GND	4
LA	5
LA	6				OQ2545BHP
LAQ	7
LAQ	8
GND	9
IBIAS	10
GND 11
VEE2 12
	13	14	15	16	17	18	19	20	21	22	23	24
	EE2	GND	EFADJ	AMPADJ	SMOD	SIMOD	SIBIAS	GND	DLOOPQ	DLOOP	GND	EE2
	V											V

36	VEE2
35	GND
34	DINQ
33	DIN
32	GND
31	i.c.
30	i.c.
29	GND
28	i.c.
27	i.c.
26	GND
25	VEE2

MGL728

Fig.4 Pin configuration of OQ2545BHP.

1999 Aug 24

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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 VEE1.

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.

The preamplifier boosts the signal to a suitable 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 the preamplifier and the emitter followers contain an output level dependent component, along with an independent component. The output level dependent component is controlled via the signal on pin SIMOD and 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. The output 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 compatible input and at HIGH-level it can 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

The loop mode is provided for system testing. A LOW-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

50 Ω

50 Ω

DIN, DLOOP

DINQ, DLOOPQ,

CIN, CLOOP

CINQ, CLOOPQ

VEE1	MGL731

Fig.5 Schematic for CML differential inputs.

1999 Aug 24

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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.

If a laser diode is used and connected between pin LA and 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 VEE1. When left open-circuit, pin SMOD is 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).

The ratio between the current into pin SIMOD and the total modulation current depends on the polarity setting via pin SMOD. When pin SMOD = 0 V the value of

Imod = 92 × ISIMOD (approximately) and whereas

pin SMOD = VEE1 the value of Imod = 107 × ISIMOD (approximately).

4 kΩ	100 Ω	100 Ω
ISIMOD		LA
SIMOD
		LAQ
	+	−

k × ISIMOD 71 × k × ISIMOD(1)

VEE2

MGL733

(1)k = 1.3 when pin SMOD = 0 V. k = 1.5 when pin SMOD = VEE1.

Fig.6 Schematic of laser modulation outputs.

1999 Aug 24

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