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参数资料
| 型号： | SY88982LMG TR |
| 厂商： | Micrel Inc |
| 文件页数： | 8/10页 |
| 文件大小： | 0K |
| 描述： | IC LASER DRVR 2.7GBPS 3.6V 16MLF |
| 标准包装： | 1,000 |
| 类型： | 激光二极管驱动器（光纤） |
| 数据速率： | 2.7Gbps |
| 通道数： | 1 |
| 电源电压： | 3 V ~ 3.6 V |
| 电流 - 电源： | 48mA |
| 电流 - 调制： | 90mA |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 16-VFQFN 裸露焊盘，16-MLF? |
| 供应商设备封装： | 16-MLF?（3x3） |
| 包装： | 带卷 (TR) |
| 安装类型： | 表面贴装 |
| 其它名称： | SY88982LMGTR SY88982LMGTR-ND |
Micrel, Inc.
Application Information
The typical applications diagram on the first page
shows how to connect the driver to the laser, single
ended. To improve transition time and laser
response, the laser can be driven differentially as
shown in Figures 3 and 4. Driving the laser
differentially will also minimize the crosstalk with the
rest of the circuitry on the board, especially the
receiver.
DC-Coupling
In addition to the low power consumption and high
modulation current, the SY88982L offers a high
compliance voltage. As can be seen in the “Typical
Operating Characteristics” section (I MOD vs. V MOD
curves), the minimum voltage needed at the output
of the driver for proper operation is less than 600mV,
leaving a large headroom, V CC -600mV, to the laser
with the damping resistor. To show the importance
of this high compliance voltage, consider the voltage
drops along the path from V CC to ground through the
laser, damping resistor, and driver:
V CC = Driver Headroom + V Rd + V laser
V Rd = Rd x I MOD
V laser = V band-gap + R laser x I MOD + Ldi/dt
V band-gap + R laser x I MOD = 1.6V at maximum for
a Fabry Perrot or a DFB laser.
Ldi/dt is the voltage drop due to the laser parasitic
inductance during I MOD transitions. Assuming L =
1nH, t f = t f = 80ps (measured between 20% and 80%
of I MOD ), and I MOD = 70mA (42mA from 20% to 80%),
then Ldi/dt will be equal to 525mV. This number can
be minimized by making the laser leads as short as
possible and using and RC compensation network
between the cathode of the laser and ground or
across the laser driver outputs as shown in Figure 3.
To be able to drive the laser DC-coupled with a high
current, it is necessary to keep the damping resistor
as small as possible. For example, if the drop due to
parasitic inductance of the laser is neglected
(compensated for) and the maximum drop across
the laser (1.6V) considered while keeping a
minimum of 600mV headroom for the driver, then
the maximum damping resistor that allows a 70mA
modulation current into the laser is:
R dmax = (V CC -0.6V-1.6V)/0.07A
The worst case will be with V CC = 3.0V,
leading to R dmax = 11.4 ?
On the other hand, the small is the value of R d , the
higher is the overshoot/undershoot on the optical
signal from the laser. In the circuit shown in Figure 3,
the RC compensation network across the driver
SY88982AL
outputs (MOD+ and MOD-) allows the user R d =
10 ?. The optical eye diagrams at data rates of
155Mbps/622Mbps/1.25Gbps/2.5Gbps, shown in
“Functional Characteristics” section, are all obtained
with the same circuit using R d = 10 ?, R Comp = 100 ?,
and C Comp = 3pF. The compensation network may
change from one board to another and from one
type of laser to another. An additional compensation
network (RC) can be added at the laser cathode for
further compensation and eye smoothing.
Figure 3. Laser DC-Coupled
AC-Coupling
When trying to AC couple the laser to the driver, the
headroom of the driver is no longer a problem since
it is DC isolated from the laser with the coupling
capacitor. At the output, the headroom of the driver
is determined by the pull-up network. In Figure 4, the
modulation current out of the driver is split between
the pull-up network and the laser. If, for example, the
total pull-up resistor is twice the sum of the damping
resistor and laser equivalent series resistance, only
two thirds (2/3) of the modulation current will be
used by the laser. So, to keep most of the
modulation current going through the laser, the total
pull-up resistor must be kept as high as possible.
One solution consists in using an inductor alone as
pull-up, presenting a high impedance path for the
?
modulation current and zero ohm (0 ) path for the
DC current offering a headroom of the driver equal
to V CC and almost all the modulation current goes
into the laser. The inductor alone will cause signal
distortion, and, to improve that, a combination of
resistors and inductors can be used (as shown on
Figure 4). In this case, the headroom of the driver is
V CC -R1 x α I MOD , where α I MOD is the portion of the
modulation current that goes through the pull-up
network.
When the laser is AC-coupled to the driver, the
coupling capacitor creates a low-frequency cutoff in
the circuit, and its value must be chosen as large as
December 2009
8
M9999-121009-A
hbwhelp@micrel.com or (408) 955-1690
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相关代理商/技术参数 |
参数描述 |
|---|---|
| SY88983V | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:3.3V/5V 3.2Gbps CML LOW-POWER LIMITING POST AMPLIFIER w/TTL SD |
| SY88983VKG | 功能描述:限幅放大器 3.3V-5V 3.2 Gbps CML Post Amp:1xSD gain/1xTC/10 pin MSOP/bulk (I Temp, Green) RoHS:否 制造商:Micrel 输入电压范围（最大值）:3.6 V 工作电源电压:3.3 V 电源电流:40 mA 工作温度范围:- 40 C to + 85 C 封装 / 箱体:MSOP-10 封装:Tube |
| SY88983VKG TR | 功能描述:限幅放大器 3.3V-5V 3.2 Gbps CML Post Amp: 1xSD gain/1xTC/10 pin MSOP/ PbSn/ T+R (I Temp, Green) RoHS:否 制造商:Micrel 输入电压范围（最大值）:3.6 V 工作电源电压:3.3 V 电源电流:40 mA 工作温度范围:- 40 C to + 85 C 封装 / 箱体:MSOP-10 封装:Tube |
| SY88983VKI | 功能描述:IC AMP POST 5/3.3V TTL SD 10MSOP RoHS:否 类别:集成电路 (IC) >> 线性 - 放大器 - 专用 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:60 系列:- 类型:可变增益放大器 应用:CATV 安装类型:表面贴装 封装/外壳:20-WQFN 裸露焊盘 供应商设备封装:20-TQFN-EP（5x5） 包装:托盘 |
| SY88983VKI TR | 功能描述:IC AMP POST 5/3.3V TTL SD 10MSOP RoHS:否 类别:集成电路 (IC) >> 线性 - 放大器 - 专用 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:60 系列:- 类型:可变增益放大器 应用:CATV 安装类型:表面贴装 封装/外壳:20-WQFN 裸露焊盘 供应商设备封装:20-TQFN-EP（5x5） 包装:托盘 |
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