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參數(shù)資料
| 型號： | TZA3001U |
| 廠商： | NXP SEMICONDUCTORS |
| 元件分類： | 其它接口 |
| 英文描述： | SDH/SONET STM4/OC12 laser drivers |
| 中文描述： | SPECIALTY INTERFACE CIRCUIT, UUC40 |
| 封裝： | 2 X 2 X 0.38 MM, DIE-40 |
| 文件頁數(shù)： | 8/22頁 |
| 文件大?。?/td> | 517K |
| 代理商： | TZA3001U |
1999 Aug 24
8
Philips Semiconductors
Preliminary specification
SDH/SONET STM4/OC12 laser drivers
TZA3001AHL; TZA3001BHL;
TZA3001U
Example:
A laser with an MPD has the following
specifications: P
O
= 1 mW, I
th
= 25 mA,
η
EO
= 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
around the optical ZERO level is 50% of
η
EO
around the
optical ONE level, due to the decreasing slope near the
threshold level.
Inthisexamplethe resultingbandwidth forthe opticalONE
regulation loop, without external capacitance, would be:
3
–
×
2
π
40
×
10
×
80
×
The resulting bandwidth for the optical ZERO regulation
loop, without external capacitance, would be:
3
–
2
π
40
×
10
×
×
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
(
τ
ONE
and
τ
ZERO
), 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
thecorrespondingcurrentsaregivenastransconductance
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 G
and an extremely low
input leakage current (pA range).
B
ONE
10
10
×
3
–
12
–
10
3
----30
750 Hz
≈
=
B
ZERO
0.5
30
×
10
10
10
3
3
–
×
×
12
–
50
600 Hz
≈
=
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
μ
A 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 k
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
τ
ONE
and
τ
ZERO
, 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 V
CC(R)
. The resistor values can be
calculated using the following formulae:
1500
×
I
BIAS(max)
(9)
(10)
R
ALARMHI
1.5
=
[
]
R
ALARMLO
BIAS(min)
300
×
I
=
[
]
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| TZA3004 | SDH/SONET STM1/OC3 and STM4/OC12 transceiver |
| TZA3004HL | SDH/SONET data and clock recovery unit STM1/4 OC3/12 |
| X00602 | SENSITIVE GATE SCR |
| X00602MA | 0.8A SCRs |
| X00602MA1AA2 | 0.8A SCRs |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TZA3004 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:SDH/SONET STM1/OC3 and STM4/OC12 transceiver |
| TZA3004HL | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:SDH/SONET data and clock recovery unit STM1/4 OC3/12 |
| TZA3005 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:SDH/SONET STM1/OC3 and STM4/OC12 transceiver |
| TZA3005H | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:SDH/SONET STM1/OC3 and STM4/OC12 transceiver |
| TZA3011A | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:30 Mbits/s up to 3.2 Gbits/s A-rate(TM) laser drivers |
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