Philips TZA3001BHL-C1 Datasheet

DATA SH EET

Product specification
Supersedes data of 2000 Jan 31
File under Integrated Circuits, IC19

2000 Feb 22

INTEGRATED CIRCUITS

TZA3001AHL; TZA3001BHL;
TZA3001U

SDH/SONET STM4/OC12 laser
drivers

2000 Feb 22 2

Philips Semiconductors Product specification

SDH/SONET STM4/OC12 laser drivers

TZA3001AHL; TZA3001BHL;

TZA3001U

FEATURES

• 622 Mbits/s data input, bothCurrent Mode Logic (CML)
and Positive Emitter Coupled Logic (PECL) compatible;
maximum 800 mV (p-p)

• Adaptive laser output control with dual loop, stabilizing
optical 1 and 0 levels

• Optionalexternalcontroloflasermodulationandbiasing
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 5 × 5 plastic package

• Single 5 V power supply.

TZA3001AHL

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

TZA3001BHL

• ExtraSTM4 622 Mbits/s loop mode input; both CML and
PECL compatible.

TZA3001U

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

APPLICATIONS

• SDH/SONET STM4/OC12 optical transmission systems

• SDH/SONET STM4/OC12 optical laser modules.

GENERAL DESCRIPTION

The TZA3001AHL, TZA3001BHL and TZA3001U are fully
integrated laser drivers for STM4/OC12 (622 Mbits/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.

TheTZA3001AHL features an alarm functionforsignalling
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 TZA3001BHL is provided with an additional RF data
input to allow remote system testing (loop mode).

The TZA3001U is a bare die version for use in compact
laser module designs. The die contains 40 pads and
features the combined functionality of the TZA3001AHL
and the TZA3001BHL.

ORDERING INFORMATION

TYPE

NUMBER

PACKAGE

NAME DESCRIPTION VERSION

TZA3001AHL LQFP32 plastic low profile quad flat package; 32 leads; body 5 × 5 × 1.4 mm SOT401-1
TZA3001BHL
TZA3001U − bare die; 2000 × 2000 × 380 µm −

2000 Feb 22 3

Philips Semiconductors Product specification

SDH/SONET STM4/OC12 laser drivers

TZA3001AHL; TZA3001BHL;

TZA3001U

BLOCK DIAGRAM

handbook, full pagewidth

LASER

CONTROL

BLOCK

BAND GAP

REFERENCE

data input

(differential)

TZA3001AHL

CURRENT

SWITCH

ALARMHITZERO

2

DIN

MONIN

28

18

ALARMLO

215

TONE

4

ALARM

26

22

ONE

23

ZERO

13

LA

DINQ

29

12

LAQ

15

BIAS

6

BGAP

MGK271

ALS

31

V

CC(B)

10

GND

1, 3, 8, 9,
11, 14, 16, 17
24, 25, 32

V

CC(G)

7

V

CC(R)

19, 20
27, 30

411

Fig.1 Block diagram of TZA3001AHL.

handbook, full pagewidth

MGK270

LASER

CONTROL

BLOCK

BAND GAP

REFERENCE

TZA3001BHL

CURRENT

SWITCH

MUX

TZERO

ALS

2

DLOOP

MONIN

19

31

V

CC(B)

10

GND

1, 3, 8, 9,
11, 14, 16, 17
24, 25, 32

V

CC(G)

7

ENL

26 5

TONE

4

22

ONE

23

ZERO

13

LA

DLOOPQ

20

DIN

28

DINQ

29

12

LAQ

15

BIAS

6

BGAP

V

CC(R)

18, 21
27, 30

411

Fig.2 Block diagram of TZA3001BHL.

2000 Feb 22 4

Philips Semiconductors Product specification

SDH/SONET STM4/OC12 laser drivers

TZA3001AHL; TZA3001BHL;

TZA3001U

PINNING

SYMBOL

PIN PAD

DESCRIPTION

TZA3001AHL TZA3001BHL TZA3001U

GND 1 1 1 ground
MONIN 2 2 2 monitor photodiode current input
GND 3 3 3 ground
IGM −−4 not connected
TONE 4 4 5 connection for external capacitor used for setting

optical 1 control loop time constant (optional)

TZERO 5 5 6 connection for external capacitor used for setting

optical 0 control loop time constant (optional)
BGAP 6 6 7 connection for external band gap decoupling capacitor
V

CC(G)

7 7 8 supply voltage (green domain); note 1

V

CC(G)

−−9 supply voltage (green domain); note 1
GND 8 8 10 ground
GND 9 9 11 ground
V

CC(B)

10 10 12 supply voltage (blue domain); note 2

V

CC(B)

−−13 supply voltage (blue domain); note 2
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
V

CC(R)

− 18 23 supply voltage (red domain); note 3
V

CC(R)

19 −−supply voltage (red domain); note 3
DLOOP − 19 24 loop mode data input
V

CC(R)

20 −−supply voltage (red domain); note 3
DLOOPQ − 20 25 loop mode data input inverted
V

CC(R)

−−26 supply voltage (red domain); note 3
ALARMLO 21 − 27 minimum bias current alarm reference level input
V

CC(R)

− 21 − supply voltage (red domain); note 3
ONE 22 22 28 optical 1 reference level input
ZERO 23 23 29 optical 0 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
V

CC(R)

27 27 34 supply voltage (red domain); note 3

2000 Feb 22 5

Philips Semiconductors Product specification

SDH/SONET STM4/OC12 laser drivers

TZA3001AHL; TZA3001BHL;

TZA3001U

Notes

1. Supply voltage for the Monitor PhotoDiode (MPD) input current.

2. Supply voltage for the laser modulation outputs (LA, LAQ).

3. Supply voltage for the data inputs (DIN, DINQ), optical 1 and 0 reference level inputs (ONE, ZERO), and the bias
current alarm reference level inputs (ALARMHI, ALARMLO).

DIN 28 28 35 data input
DINQ 29 29 36 data input inverted
V

CC(R)

30 30 37 supply voltage (red domain); note 3
ALS 31 31 38 automatic laser shutdown input
GND 32 32 39 ground
GND −−40 ground

SYMBOL

PIN PAD

DESCRIPTION

TZA3001AHL TZA3001BHL TZA3001U

handbook, full pagewidth

TZA3001AHL

MGK273

1
2
3
4
5
6
7
8

24
23
22
21
20
19
18
17

9

10

11

12

13

14

15

16

32

31

30

29

28

27

26

25

GND

MONIN

GND

TONE

TZERO

BGAP

V

CC(G)

GND

GND

V

CC(B)

GND

LAQ

GND

BIAS

GND

LA

GND

ALARMHI

V

CC(R)

ONE
ALARMLO

ZERO

V

CC(R)

GND

GND

DIN

DINQ

V

CC(R)

ALS

GND

ALARM

V

CC(R)

Fig.3 Pin configuration of TZA3001AHL.

2000 Feb 22 6

Philips Semiconductors Product specification

SDH/SONET STM4/OC12 laser drivers

TZA3001AHL; TZA3001BHL;

TZA3001U

handbook, full pagewidth

TZA3001BHL

MGK272

1
2
3
4
5
6
7
8

24
23
22
21
20
19
18
17

9

10

11

12

13

14

15

16

32

31

30

29

28

27

26

25

GND

MONIN

GND

TONE

TZERO

BGAP

V

CC(G)

GND

GND

V

CC(B)

GND

LAQ

GND

BIAS

GND

LA

GND

V

CC(R)

DLOOPQ

ONE
V

CC(R)

ZERO

DLOOP

GND

GND

DIN

DINQ

V

CC(R)

ALS

GND

ENL

V

CC(R)

Fig.4 Pin configuration of TZA3001BHL.

FUNCTIONAL DESCRIPTION

The TZA3001AHL, TZA3001BHL and TZA3001U laser
drivers accept a 622 Mbits/s STM4 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);
see Fig.5. The input signal can be at a CML level of
approximately 200 mV (p-p) below the supply voltage, or
at a PECL level up to 800 mV (p-p). The inputs can be
configured to accept CML signals by connecting pins DIN
and DINQ to V

CC(R)

via external 50 Ω pull-up resistors.
If PECL compatibility is required, the usual Thevenin
termination can be applied.

handbook, full pagewidth

MGS910

10 kΩ 10 kΩ

DINQ, DLOOPQDIN, DLOOP

100 Ω

GND

V

CC(R)

100 Ω

Fig.5 DIN/DINQ and DLOOP/DLOOPQ inputs.

2000 Feb 22 7

Philips Semiconductors Product specification

SDH/SONET STM4/OC12 laser drivers

TZA3001AHL; TZA3001BHL;

TZA3001U

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 or HIGH) will cause the device to be 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
able to operate at the large peak currents required at the
output laser driver 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 to
pins LA and LAQ (see Fig.6). The BIAS pin outputs 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 (see Fig.7).

Automatic laser control

A laser with a Monitor PhotoDiode (MPD) is required for
the laser control circuit (see application diagrams
Figs 18 and 19).

The MPD current is proportional to the laser emission and
is applied to pin MONIN. The MPD current range is
100 to 1000 µA (p-p).Theinputbufferisoptimizedtocope
with an MPD capacitance of up to 50 pF. To prevent the
input buffer from oscillating if the MPD capacitance is low,
thecapacitanceshouldbeincreasedtotheminimumvalue
specified in Chapter “Characteristics”, by connecting a
capacitor between pin MONIN and V

CC(G)

.

DC reference currents are applied to pins ONE and ZERO
to set the MPD reference levels for laser HIGH and laser
LOW respectively. This is adequately achieved by using
resistors to connect V

CC(R)

to pins ONE and ZERO,
(see Fig.8), however, current DACs can also be used.
The voltages on pins ONE and ZERO are held at a
constantlevelof1.5 VbelowV

CC(R)

.Thereferencecurrent
applied to pin ONE is internally multiplied by 16 and the
reference current flowing into pin ZERO is internally
multipliedby 4. The accuracy of the V

CC(R)

− 1.5 Vvoltage
at pins ONE and ZERO is described in Section “Accuracy
of voltage on inputs: ONE, ZERO, ALARMLO, ALARMHI”.

handbook, halfpage

MGS906

GND

LA LAQ

ALS

TR

TR

n

Fig.6 LA and LAQ outputs.

handbook, halfpage

MGS907

GND

BIAS

ALS

TR

TR

n

Fig.7 Laser driver bias current output circuit.

handbook, halfpage

MGS908

V

CC(R)

GND

ONE, ZERO, ALARMLO, ALARMHI

50 µA

30 kΩ

Fig.8 ONE, ZERO, ALARMLO and ALARMHI

inputs.

2000 Feb 22 8

Philips Semiconductors Product specification

SDH/SONET STM4/OC12 laser drivers

TZA3001AHL; TZA3001BHL;

TZA3001U

The reference current and the resistor for the optical 1
modulation current control loop is calculated using the
following formulae:

(1)

(2)

The reference current and resistor for the optical 0 bias
current control loop is calculated using the following
formulae:

(3)

(4)

In these formulae, I

MPD(ONE)

and I

MPD(ZERO)

represent the
MPD current during an optical 1 and an optical 0 period,
respectively.

EXAMPLE
A laser operates at optical output power levels of 0.3 mW

forlaserHIGHand0.03 mW for laser LOW (extinction ratio
of 10 dB). Suppose the corresponding MPD currents for
this particular laser are 260 and 30 µA, respectively.

In this example, the reference current flowing into
pin ONE is:

This current can be set usinga current source or simply by
a resistor of the appropriate value connected between
pin ONE and V

CC(R)

.

In this example, the resistor is:

In this example, the reference current at pin ZERO is:

and can be set using a resistor:

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

Designing the modulation and bias current control
loop

The optical 1 and 0 current control loop time constantsare
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 a
capacitor between pins TZERO and TONE.

The optical 1 modulation current control loop time
constant (τ)and bandwidth (B) can be estimatedusing the
following formulae:

(5)

(6)

The optical 0 bias current control loop time constant and
bandwidth can be estimated using the following formulae:

(7)

(8)

The term η

LASER

(dimensionless) in the above formulae is

the product of the following two terms:

•ηEO is the electro-optical efficiency which accounts for

thesteepness of the laser slope characteristic. It defines
the rate at which the optical output powerincreases with
modulation current, and is measured in W/A.

• R is the MPD responsivity. It determines the amount of
MPD current for a given value of optical output power,
and is measured in A/W.

EXAMPLE
A laser with an MPD has the following specifications:

PO= 1 mW, Ith= 25 mA, ηEO= 30 mW/A, R = 500 mA/W.
The term I

th

is the required threshold current to switch on
the laser. If the laser operates just above the threshold
level, it may be assumed that η

EO

near the optical 0 level

is 50% of η

EO

near the optical 1 level, due to the slope

decreasing near the threshold level.

I

ref ONE()

1

16

------

I

MPD(ONE)

×= A[]

R

ONE

1.5

I

ONE

-----------

24

I

MPD(ONE)

------------------------

== Ω[]

I

ref ZERO()

1
4

-- -

I

MPD(ZERO)

×= A[]

R

ZERO

1.5

I

ZERO

--------------

6

I

MPD(ZERO)

---------------------------

== Ω[]

I

ref ONE()

1

16

------

260 10×

6–

× 16.25 µA==

R

ONE

1.5

16.25 106–×

-------------------------------- -

92.3 kΩ==

I

ref ZERO()

1
4

-- -

30 10

6–

×× 7.5 µA==

R

ZERO

1.5

7.5 106–×

--------------------------

200 kΩ==

τ

ONE

40 10

12–

C

TONE

+×()

80 10

3

×

η

LASER

----------------------

×= s[]

B

ONE

1

2πτ

ONE

×

------------------------- -

= Hz[]

B

ONE

η

LASER

2π 40 10

12–

× C

TONE

+()× 80× 103×

-------------------------------------------------------------------------------------------------

Hz[]=

τ

ZERO

40 10

12–

C

TZERO

+×()

50 10

3

×

η

LASER

----------------------

×= s[]

B

ZERO

1

2πτ

ZERO

×

----------------------------

= Hz[]

B

ZERO

η

LASER

2π 40 10

12–

C

TZERO

+×()× 50× 103×

----------------------------------------------------------------------------------------------------

Hz[]=

2000 Feb 22 9

Philips Semiconductors Product specification

SDH/SONET STM4/OC12 laser drivers

TZA3001AHL; TZA3001BHL;

TZA3001U

In this example, the resulting bandwidth for the optical 1
modulation current control loop, without an external
capacitor, is:

The resulting bandwidth for the optical 0 bias current
control loop, without an external capacitor, is:

It is not necessary to add additional capacitance with this
type of laser.

Control loop data pattern and bit rate dependency

The constants in equations (1) and (3) are valid when the
data pattern frequently contains a sufficient number of
‘constantzeroes’and‘constantones’.A single control loop
time period (τ

ONE

and τ

ZERO

) must contain ones and zeros
for at least approximately 6 ns (as provided, for example,
by the A1/A2 frame alignment bytes for STM4/OC12).
In practice, the optical extinction ratio increases if the bit
rate increases. Therefore, it is important to use the actual
data patterns and bit rate of the final application circuit for
adjusting the optical levels.

The laser driver peak detectors are able to track MPD
output current overshoot and undershoot conditions.
Unfortunately, these conditions affect the ability of the IC
to correctly interpret the high and low level MPD current.
In particular, the occurrence of undershoot can have a
markedly adverse effect on the interpretation of the low
level MPD current.

Additional bias by modulation ‘off’ current

Although during operation, the full modulation current
switches between outputs LA and LAQ, a small amount of
modulation current continues to flow through the inactive
pin.

For example, when the laser, whose cathode is connected
to LA, is in the ‘dark’ part of its operating cycle (logic 0),
someof the modulation ‘off’ current flows through LA while
most of the current flows through LAQ. This value
I

o(mod)(off)

is effectively added to the bias current and is
subtracted from the modulation current. Fortunately, the
value correlates closely with the magnitude of the
modulation current. Therefore, applications requiring low
bias and low modulation are less affected. Figure 9 shows
the modulation ‘off’ current as a function of the modulation
‘on’ current.

Monitoring the bias and modulation current

Although not recommended, the bias and modulation
currentsgenerated by the laser driver can bemonitored by
measuring the voltages on pins TZERO and TONE,
respectively (see Fig.10). The relationship between these
voltages and the corresponding currents are given as
transconductance values and are specified in
Chapter “Characteristics”. The voltages on pins TZERO
and TONE range from 1.4 to 3.4 V. Any connection to
these pins should have a very high impedance value. It is
mandatory to use a CMOS buffer or an amplifier with an
input impedance higher than 100 GΩ and with an
extremely low input leakage current (pA).

B

ONE

30 103–× 500× 103–×

2π 40× 10

12–

× 80× 103×

---------------------------------------------------------------------

750 Hz≈=

B

ZERO

0.5 30× 103–× 500× 103–×
2π 40× 10

12–

× 50× 103×

-------------------------------------------------------------------------

600 Hz≈=

handbook, halfpage

0 204060

3

1

0

2

MGS902

I

o(mod)(on)

(mA)

(2)

(1)

I

o(mod)(off)

(mA)

Fig.9 I

o(mod)(off)

as a function of I

o(mod)(on)

.

(1) Worst case operation (Tj= 125 °C, VCC= 5.5 V

and worst case parameter processes).

(2) Typical operation.

2000 Feb 22 10

Philips Semiconductors Product specification

SDH/SONET STM4/OC12 laser drivers

TZA3001AHL; TZA3001BHL;

TZA3001U

Automatic laser shut-down and laser slow start

The laser modulation and bias currents can be rapidly
switched off when a HIGH level (CMOS) is applied to
pin ALS. This function allows the circuit to be shut-down in
the event of an optical system malfunction. A 25 kΩ
pull-down resistor defaults pin ALS to the non active state
(see Fig.11).

When a LOW level is applied to pin ALS, the modulation
and bias currents slowly increase to the desired values at
the typical time constants of τ

ONE

and τ

ZERO

, respectively.

This can be used to slow-start the laser.

Manual laser override

The automatic laser control function can be overridden by
connecting voltage sources to pins TZERO and TONE to
take direct control of the current sources for bias and
modulation respectively. The control voltages should
range from 1.4 to 3.4 V to swing the modulation current
over the range 1 to 60 mA and the bias current over the
range 1 to 90 mA. These current ranges are guaranteed.

Due to the tolerance range in the manufacturing process,
some devices may have higher current values than those
specified, as shown in Figs 12 and 13. Both figures show
thattemperature changes cause a slight tilting of the linear
characteristic around an input voltage of 2.4 V.
Consequently, the manually controlled current level is
most insensitive to temperature variations at around this
value. Bias and modulation currents in excess of the
specified range are not supported and should be avoided.

Currentsintoor out of pins TZERO and TONE in excess of
10 µA must be avoided to prevent damage to the circuit.

handbook, halfpage

MGS905

GND

40 pF

<

1 nA

LINEAR VOLTAGE TO

CURRENT CONVERTER

TZERO, TONE

2.4 V

<

1 nA

Fig.10 TZERO and TONE internal configuration.

handbook, halfpage

MGS911

25 kΩ

V

CC(R)

100 Ω

GND

ALS

100 Ω

Fig.11 ALS input.