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 pull-up resistors. If PECL compatibility is required, the usual Thevenin termination can be applied.
handbook, full pagewidth
MGS910
10 k 10 k
DINQ, DLOOPQDIN, DLOOP
100
GND
V
CC(R)
100
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 k
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)
------------------------
== []
I
ref ZERO()
1 4
-- -
I
MPD(ZERO)
×= A[]
R
ZERO
1.5
I
ZERO
--------------
6
I
MPD(ZERO)
---------------------------
== []
I
ref ONE()
1
16
------
260 10×
6–
× 16.25 µA==
R
ONE
1.5
16.25 106–×
-------------------------------- -
92.3 k==
I
ref ZERO()
1 4
-- -
30 10
6–
×× 7.5 µA==
R
ZERO
1.5
7.5 106–×
--------------------------
200 k==
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× 10
-------------------------------------------------------------------------------------------------
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× 10
----------------------------------------------------------------------------------------------------
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 G and with an extremely low input leakage current (pA).
B
ONE
30 103–× 500× 103–×
2π 40× 10
12
× 80× 10
---------------------------------------------------------------------
750 Hz=
B
ZERO
0.5 30× 103–× 500× 103–× 2π 40× 10
12
× 50× 10
-------------------------------------------------------------------------
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 k 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 k
V
CC(R)
100
GND
ALS
100
Fig.11 ALS input.
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