Philips TZA3041U, TZA3041BHL, TZA3041AHL Datasheet

INTEGRATED CIRCUITS

DATA SHEET

TZA3041AHL; TZA3041BHL; TZA3041U

Gigabit Ethernet/Fibre Channel laser drivers

Preliminary specification

1999 Aug 24

Supersedes data of 1998 Aug 24

File under Integrated Circuits, IC19

Philips Semiconductors	Preliminary specification
Gigabit Ethernet/Fibre Channel	TZA3041AHL; TZA3041BHL;
laser drivers	TZA3041U

FEATURES

∙1.2 Gbits/s data input, both Current-Mode Logic (CML) and Positive Emitter Coupled Logic (PECL) compatible; maximum 800 mV (p-p)

∙Adaptive laser output control with dual loop, stabilizing optical ONE and ZERO levels

∙Optional external control of laser modulation and biasing currents (non-adaptive)

∙Automatic laser shutdown

∙Few external components required

∙Rise and fall times of 120 ps (typical value)

∙Jitter <50 mUI (p-p)

∙RF output current sinking capability of 60 mA

∙Bias current sinking capability of 90 mA

∙Power dissipation of 430 mW (typical value)

∙Low cost LQFP32 plastic package

∙Single 5 V power supply.

TZA3041AHL

∙Laser alarm output for signalling extremely low and high bias current conditions.

TZA3041BHL

∙Extra 1.2 Gbits/s loop mode input; both CML and PECL compatible.

TZA3041U

∙Bare die version with combined bias alarm and loop mode functionality.

ORDERING INFORMATION

APPLICATIONS

∙Gigabit Ethernet/Fibre Channel optical transmission systems

∙Gigabit Ethernet/Fibre Channel optical laser modules.

GENERAL DESCRIPTION

The TZA3041AHL, TZA3041BHL and TZA3041U are fully integrated laser drivers for Gigabit Ethernet/Fibre Channel (1.2 Gbits/s) systems, incorporating the RF path between the data multiplexer and the laser diode. Since the dual loop bias and modulation control circuits are integrated on the IC, the external component count is low. Only decoupling capacitors and adjustment resistors are required.

The TZA3041AHL features an alarm function for signalling extreme bias current conditions. The alarm low and high threshold levels can be adjusted to suit the application using only a resistor or a current Digital-to-Analog Converter (DAC).

The TZA3041BHL is provided with an additional RF data input to facilitate remote (loop mode) system testing.

The TZA3041U is a bare die version for use in compact laser module designs. The die contains 40 pads and features the combined functionality of the TZA3041AHL and the TZA3041BHL.

TYPE		PACKAGE
NUMBER	NAME	DESCRIPTION	VERSION
TZA3041AHL	LQFP32	plastic low profile quad flat package; 32 leads; body 5 × 5 × 1.4 mm	SOT401-1
TZA3041BHL
TZA3041U	−	bare die; 2000 × 2000 × 380 μm	−

1999 Aug 24

2

Philips Semiconductors Preliminary specification

Gigabit Ethernet/Fibre Channel	TZA3041AHL; TZA3041BHL;
laser drivers	TZA3041U
BLOCK DIAGRAMS

handbook, full pagewidth

ALARM TONE TZERO ALARMLO ALARMHI

		26	4	5	21	18
						2	MONIN
					LASER	22
					CONTROL		ONE
						23
					BLOCK		ZERO
	data input					13	LA
28	(differential)				CURRENT	12	LAQ
DIN					SWITCH
29						15
							BIAS
DINQ
	TZA3041AHL				BAND GAP	6	BGAP
					REFERENCE
					1, 3, 8, 9,
	19, 20				11, 14, 16, 17
	27, 30	7	10	31	24, 25, 32
	4				11	MBK874
VCC(R) VCC(G) VCC(B)				ALS	GND

Fig.1 Block diagram of TZA3041AHL.

handbook, full pagewidth					ENL				TONE			TZERO
							26				4		5					2
																					MONIN
															LASER			22
															CONTROL						ONE
																		23
															BLOCK						ZERO
DIN		28
																		13
DINQ		29																			LA
															CURRENT			12
		19			MUX																LAQ
DLOOP															SWITCH			15
																					BIAS
		20
DLOOPQ
															BAND GAP			6			BGAP
			TZA3041BHL												REFERENCE
															1, 3, 8, 9,
		18, 21													11, 14, 16, 17
			27, 30			7				10			31			24, 25, 32
			4													11		MBK873
		VCC(R) VCC(G) VCC(B)										ALS			GND

Fig.2 Block diagram of TZA3041BHL.

1999 Aug 24

3

Philips Semiconductors Preliminary specification

	Gigabit Ethernet/Fibre Channel					TZA3041AHL; TZA3041BHL;
	laser drivers					TZA3041U
	PINNING
	SYMBOL	PIN			PAD	DESCRIPTION
		TZA3041AHL	TZA3041BHL	TZA3041U
	GND	1	1		1	ground
	MONIN	2	2		2	monitor photodiode current input
	GND	3	3		3	ground
	IGM	−	−		4	not used; leave unbonded
	TONE	4	4		5	connection for external capacitor used to set optical
						ONE control loop time constant (optional)
	TZERO	5	5		6	connection for external capacitor used to set optical
						ZERO control loop time constant (optional)
	BGAP	6	6		7	connection for external band gap decoupling capacitor
	VCC(G)	7	7		8	supply voltage (green domain)
	VCC(G)	−	−		9	supply voltage (green domain)
	GND	8	8		10	ground
	GND	9	9		11	ground
	VCC(B)	10	10		12	supply voltage (blue domain)
	VCC(B)	−	−		13	supply voltage (blue domain)
	GND	11	11		14	ground
	LAQ	12	12		15	laser modulation output inverted
	LA	13	13		16	laser modulation output
	GND	14	14		17	ground
	BIAS	15	15		18	laser bias current output
	GND	16	16		19	ground
	GND	17	17		20	ground
	GND	−	−		21	ground
	ALARMHI	18	−		22	maximum bias current alarm reference level input
	VCC(R)	−	18		23	supply voltage (red domain)
	VCC(R)	19	−		−	supply voltage (red domain)
	DLOOP	−	19		24	loop mode data input
	VCC(R)	20	−		−	supply voltage (red domain)
	DLOOPQ	−	20		25	loop mode data input inverted
	VCC(R)	−	−		26	supply voltage (red domain)
	ALARMLO	21	−		27	minimum bias current alarm reference level input
	VCC(R)	−	21		−	supply voltage (red domain)
	ONE	22	22		28	optical ONE reference level input
	ZERO	23	23		29	optical ZERO reference level input
	GND	24	24		30	ground
	GND	25	25		31	ground
	ALARM	26	−		32	alarm output
	ENL	−	26		33	loop mode enable input
	VCC(R)	27	27		34	supply voltage (red domain)

1999 Aug 24

4

Philips Semiconductors Preliminary specification

	Gigabit Ethernet/Fibre Channel					TZA3041AHL; TZA3041BHL;
	laser drivers					TZA3041U
	SYMBOL	PIN			PAD	DESCRIPTION
		TZA3041AHL	TZA3041BHL	TZA3041U
	DIN	28	28		35	data input
	DINQ	29	29		36	data input inverted
	VCC(R)	30	30		37	supply voltage (red domain)
	ALS	31	31		38	automatic laser shutdown input
	GND	32	32		39	ground
	GND	−	−		40	ground

handbook, full pagewidth

GND		ALS		CC(R)		DINQ		DIN		CC(R)		ALARM		GND
				V						V
32		31		30		29		28		27		26		25

GND 1

MONIN 2

GND 3

TONE 4

TZA3041AHL

TZERO 5

BGAP 6

VCC(G) 7

GND 8

9		10		11		12		13		14		15		16
GND		CC(B)		GND		LAQ		LA		GND		BIAS		GND
		V

24 GND

23 ZERO

22 ONE

21 ALARMLO

20 VCC(R)

19 VCC(R)

18 ALARMHI

17 GND

MBK870

Fig.3 Pin configuration of TZA3041AHL.

1999 Aug 24

5

Philips Semiconductors	Preliminary specification
Gigabit Ethernet/Fibre Channel	TZA3041AHL; TZA3041BHL;
laser drivers	TZA3041U

handbook, full pagewidth

GND		ALS		CC(R)		DINQ		DIN		CC(R)		ENL		GND
				V						V
32		31		30		29		28		27		26		25

GND 1

MONIN 2

GND 3

TONE 4

TZA3041BHL

TZERO 5

BGAP 6

VCC(G) 7

GND 8

9		10		11		12		13		14		15		16
GND		CC(B)		GND		LAQ		LA		GND		BIAS		GND
		V

24 GND

23 ZERO

22 ONE

21 VCC(R)

20 DLOOPQ

19 DLOOP

18 VCC(R)

17 GND

MBK875

Fig.4 Pin configuration of TZA3041BHL.

FUNCTIONAL DESCRIPTION

The TZA3041AHL, TZA3041BHL and TZA3041U laser drivers accept a 1.2 Gbits/s Non-Return to Zero (NRZ) input data stream and generate an output signal with sufficient current to drive a solid state Fabry Perot (FP) or Distributed FeedBack (DFB) laser. They also contain dual loop control circuitry for stabilizing the true laser optical power levels representing logic 1 and logic 0.

The input buffers present a high impedance to the data stream on the differential inputs (pins DIN and DINQ). The input signal can be at CML level of approximately 200 mV (p-p) below the supply voltage, or at PECL level up to 800 mV (p-p). The inputs can be configured to accept CML signals by connecting external 50 Ω pull-up resistors

between pins DIN and DINQ to VCC(R). If PECL compatibility is required, the usual Thevenin termination

can be applied.

For ECL signals (negative and referenced to ground) the inputs should be AC-coupled to the signal source.

If AC-coupling is applied, a constant input signal (either low of high) will bring the device in an undefined state. To avoid this, it is recommended to apply a slight offset to the input stage. The applied offset must be higher than the specified value in Chapter “Characteristics”, but much lower than the applied input voltage swing.

The RF path is fully differential and contains a differential preamplifier and a main amplifier. The main amplifier is designed to handle large peak currents required at the output laser driving stage and is insensitive to supply voltage variations. The output signal from the main amplifier drives a current switch which supplies a guaranteed maximum modulation current of 60 mA at pins LA and LAQ. Pin BIAS delivers a guaranteed maximum DC bias current of up to 90 mA for adjusting the optical laser output to a level above its light emitting threshold.

Automatic laser control

A laser with a Monitor PhotoDiode (MPD) is required for the laser control circuit (see Figs 6 and 7).

The MPD current is proportional to the laser emission and is applied to pin MONIN. The MPD current range is from 100 to 1000 μA (p-p). The input buffer is optimized to cope with MPD capacitances up to 50 pF. To prevent the input buffer breaking into oscillation with a low MPD capacitance, it is required to increase the capacitance to the minimum value specified in Chapter “Characteristics” by connecting an extra capacitor between pin MONIN and

VCC(G).

1999 Aug 24

6

The optical ONE loop time constant and bandwidth can be

(1) estimated using the following formulae:

Philips Semiconductors	Preliminary specification
Gigabit Ethernet/Fibre Channel	TZA3041AHL; TZA3041BHL;
laser drivers	TZA3041U

DC reference currents are applied to pins ZERO and ONE to set the MPD reference levels for laser LOW and laser

HIGH. A resistor connected between pin ZERO and VCC(R) and a resistor connected between pin ONE and VCC(R) is sufficient, but current DACs can also be used.

The voltages on pins ZERO and ONE are held constant at

a level of 1.5 V below VCC(R). The reference current applied to pin ZERO is multiplied by 4 and the reference

current flowing into pin ONE is multiplied internally by 16.

The reference current and the resistor for the optical ONE regulation loop (modulation current control) can be calculated using the following formulae:

It should be noted that the MPD current is stabilized, rather than the actual laser optical output power. Deviations between optical output power and MPD current, known as ‘tracking errors’, cannot be corrected.

Designing the modulation and bias loop

The optical ONE and ZERO regulation loop time constants are determined by on-chip capacitances. If the resulting time constants are found to be too small in a specific application, they can be increased by connecting external capacitors to pins TZERO and TONE, respectively.

	1
IONE =	16------ × IMPD (ONE)		[A]
RONE =	-----------1.5 =	-------------------------24	[Ω]	(2)
	IONE	IMPD (ONE)

The reference current and resistor for the optical ZERO regulation loop (bias current control) can be calculated using the following formulae:

I		1	× I		[A]	(3)
	ZERO	= --		MPD (ZERO)
		4

τONE =	(40 × 10	–12	+ CTONE) ×		80 × 103		(5)
					---------------------	[s]
					ηLASER
BONE =	1		[Hz]				(6)
	2-------------------------π × τONE
BONE =			ηLASER
	2-------------------------------------------------------------------------------------------------π × (40 × 10–12 + C					) × 80 × 103
				TONE

	RZERO	=	1.5	=	6	[Ω]	(4)	The optical ZERO loop time constant and bandwidth can
			I-------------ZERO		I----------------------------MPD (ZERO)			be estimated using the following formulae:

In these formulae, IMPD(ONE) and IMPD(ZERO) represent the monitor photodiode current during an optical ONE and an

optical ZERO, respectively.

Example: A laser is operating at optical output power levels of 0.3 mW for laser HIGH and 0.03 mW for laser LOW (extinction ratio of 10 dB). Suppose the corresponding MPD currents for this type of laser are 260 and 30 μA, respectively.

In this example the reference current is

I		1	× 260 =	16.25 μA	and flows into pin ONE.
	ONE	= ------
		16

This current can be set using a current source or simply by a resistor of the appropriate value connected between pin ONE and VCC(R). In this example the resistor would be

	RONE =	1.5	= 92.3 kΩ
		16.25----------------

The reference current at pin ZERO in this example is

τZERO =	(40 × 10	–12	+ CTZERO) ×		50 × 103
					---------------------	[s] (7)
					ηLASER
BZERO =	1		[Hz]			(8)
	2----------------------------π × τZERO
BZERO =			ηLASER
	2----------------------------------------------------------------------------------------------------π × (40 × 10–12 + C					) × 50 × 103
				TZERO

The term ηLASER (dimensionless) in the above formulae is the product of the two terms:

∙ηEO is the electro-optical efficiency which accounts for the steepness of the laser slope. It is the amount of the extra optical output power in W/A of modulation current optical output power.

∙R is the monitor photodiode responsivity. It is the amount of the extra monitor photodiode current in A/W optical output power.

I			1		and can be set using a resistor
	ZERO	= -- × 30 = 7.˙5 μA
			4
RZERO		=	1.5	= 200 kΩ
			---------
			7.5

1999 Aug 24

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