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零件编号 | TZA3001U | ||
描述 | SDH/SONET STM4/OC12 laser drivers | ||
制造商 | NXP Semiconductors | ||
LOGO | |||
1 Page
INTEGRATED CIRCUITS
DATA SHEET
TZA3001AHL; TZA3001BHL;
TZA3001U
SDH/SONET STM4/OC12 laser
drivers
Preliminary specification
Supersedes data of 1997 Sep 08
File under Integrated Circuits, IC19
1999 Aug 24
Philips Semiconductors
SDH/SONET STM4/OC12 laser drivers
Preliminary specification
TZA3001AHL; TZA3001BHL;
TZA3001U
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 Ith is the required threshold
current to switch-on the laser. If the laser operates just
above the threshold level, it may be assumed that ηEO
around the optical ZERO level is 50% of ηEO around the
optical ONE level, due to the decreasing slope near the
threshold level.
In this example the resulting bandwidth for the optical ONE
regulation loop, without external capacitance, would be:
BONE = -2---π--3---0×-----×4---0--1---0×----–-1-3--0--×--–--1-5--2-0---×0-----8×---0--1---×-0---–-1--3-0----3- ≈ 750 Hz
The resulting bandwidth for the optical ZERO regulation
loop, without external capacitance, would be:
BZERO = 0---2-.--5-π---×-×----3-4---0-0---×-×----1-1---0-0--–-–--3-1--2-×---×-5----05---00-----××-----11---00----–3--3- ≈ 600 Hz
It is not necessary to add additional capacitance with this
type of laser.
Data pattern and bit rate dependency of the control
loop
The constants in Equations (1) and (3) are valid, provided
a frequent presence of sufficiently long runs of ‘constant
zero’ and ‘constant one’. The longest run of zeros and
ones, occurring typically within a single loop time period
(τONE and τZERO), must be at least approximately 6 ns
(e.g. as provided by the A1/A2 frame alignment bytes for
STM4/OC12). In practice, it can be witnessed that the
optical extinction ratio will increase if the bit rate is
increased. Therefore it is important to use the actual data
patterns and bit rate of the final application circuit for
adjusting the optical levels.
Monitoring the bias and modulation current
Although not recommended, the bias and modulation
currents generated by the laser driver can be monitored by
measuring the voltages on pins TZERO and TONE,
respectively. The relations 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. The impedance connected at these pins
should have an extremely high value. It is mandatory to
use a CMOS buffer or an amplifier with an input
impedance higher than 100 GΩ and an extremely low
input leakage current (pA range).
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, respectively, the bias current source
and the modulation current source. The control voltages
should be in the range from 1.4 to 3.4 V to sweep the
modulation current through the range from 1 to 60 mA and
the bias current through the range from 1 to 90 mA. These
current ranges are guaranteed. Depending on the
temperature and manufacturing process spread, current
values higher than the specified ranges can be achieved.
However, bias and modulation currents in excess of the
specified range are not supported and should be avoided.
Currents into or out pins TZERO and TONE in excess of
10 µA must be avoided to prevent damage of the circuit.
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 the input of pin ALS to the
non active state.
When a LOW-level is applied to pin ALS, the modulation
and bias current slowly increase to the desired values with
the typical time constants of τONE and τZERO, respectively.
This can be used as a laser slow start.
Bias alarm for TZA3001AHL
The bias current alarm circuit detects and flags whenever
the bias current is outside a predefined range. This feature
can detect excessive bias current due to laser aging and
laser malfunctioning. The maximum permitted bias current
should be applied to pin ALARMHI with an attenuation
ratio of 1500; the minimum to pin ALARMLO with an
attenuation ratio of 300.
Like the reference currents for the laser current control
loop, the alarm reference currents can be set using
external resistors connected between pins ALARMHI
or ALARMLO and VCC(R). The resistor values can be
calculated using the following formulae:
RALARMHI = 1---I-.-B-5--I-A-×--S---(1-m---5-a--0-x--)0--
[Ω]
(9)
RALARMLO = 1--I--B.--5-I-A--×-S---(-3m----0i-n--0-)-
[Ω]
(10)
1999 Aug 24
8
Philips Semiconductors
SDH/SONET STM4/OC12 laser drivers
Preliminary specification
TZA3001AHL; TZA3001BHL;
TZA3001U
BONDING PADS
SYMBOL
GND
MONIN
GND
IGM
TONE
TZERO
BGAP
VCC(G)
VCC(G)
GND
GND
VCC(B)
VCC(B)
GND
LAQ
LA
GND
BIAS
GND
GND
GND
ALARMHI
PAD
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
COORDINATES(1)
X
−664
−524
−367
−227
−70
+87
+244
+384
+524
+664
+910
+910
+910
+910
+910
+910
+910
+910
+910
+910
+681
+541
Y
−910
−910
−910
−910
−910
−910
−910
−910
−910
−910
−630
−490
−350
−210
−70
+70
+210
+350
+490
+630
+910
+910
SYMBOL PAD
COORDINATES(1)
XY
VCC(R)
DLOOP
23 +384
24 +227
DLOOPQ
25 +87
VCC(R)
26 −70
ALARMLO 27 −210
ONE
28 −367
ZERO
29 −524
GND
30 −681
GND
31 −910
ALARM
32 −910
ENL 33 −910
VCC(R)
DIN
34 −910
35 −910
DINQ
36 −910
VCC(R)
ALS
37 −910
38 −910
GND
39 −910
GND
40 −910
+910
+910
+910
+910
+910
+910
+910
+910
+681
+541
+384
+227
+70
−70
−227
−367
−551
−664
Note
1. All x and y coordinates represent the position of the
centre of the pad in µm with respect to the centre of the
die (see Fig.8).
1999 Aug 24
16
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页数 | 22 页 | ||
下载 | [ TZA3001U.PDF 数据手册 ] |
零件编号 | 描述 | 制造商 |
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TZA3001AHL | SDH/SONET STM4/OC12 laser drivers | NXP Semiconductors |
TZA3001BHL | SDH/SONET STM4/OC12 laser drivers | NXP Semiconductors |
TZA3001U | SDH/SONET STM4/OC12 laser drivers | NXP Semiconductors |
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