参数资料
型号: ADN2847ACPZ-32-RL7
厂商: Analog Devices Inc
文件页数: 10/16页
文件大小: 0K
描述: IC LSR DRVR 3.3GBPS 3.6V 32LFCSP
标准包装: 1,500
类型: 激光二极管驱动器(光纤)
数据速率: 3.3Gbps
通道数: 1
电源电压: 3 V ~ 3.6 V
电流 - 电源: 50mA
电流 - 调制: 80mA
电流 - 偏置: 100mA
工作温度: -40°C ~ 85°C
封装/外壳: 32-VFQFN 裸露焊盘,CSP
供应商设备封装: 32-LFCSP-VQ(5x5)
包装: 带卷 (TR)
安装类型: 表面贴装
ADN2847
The laser degrade alarm, DEGRADE, is provided to give a
warning of imminent laser failure if the laser diode degrades
further or environmental conditions continue to stress the LD,
such as increasing temperature.
The laser fail alarm, FAIL, is activated when the transmitter can
no longer be guaranteed to be SONET/SDH compliant. This
occurs when one of the following conditions arises:
Data Sheet
If the ID_TONE function is not used, the IDTONE pin should
be tied to V CC . Note that using IDTONE during transmission
can cause optical eye degradation.
DATA AND CLOCK INPUTS
Data and clock inputs are ac-coupled (10 nF capacitors are
recommended) and terminated via a 100 Ω internal resistor
between DATAP and DATAN, and also between the CLKP pin
?
?
The ASET threshold is reached.
The ALS pin is set high. This shuts off the modulation and
bias currents to the LD, resulting in the MPD current
dropping to zero. This gives closed-loop feedback to the
system that ALS has been enabled.
and the CLKN pin. There is a high impedance circuit to set the
common-mode voltage that is designed to allow for maximum
input voltage headroom over temperature. It is necessary that ac
coupling is used to eliminate the need for matching between
common-mode voltages.
DEGRADE is raised only when the bias current exceeds 90% of
ADN2847
ASET current.
MONITOR CURRENTS
IBMON, IMMON, IMPDMON, and IMPDMON2 are current
controlled current sources from V CC . They mirror the bias,
modulation, and MPD current for increased monitoring
functionality. An external resistor to GND gives a voltage
proportional to the current monitored.
If the monitoring functions IMPDMON and IMPDMON2 are
not required, the IMPD pin and the IMPD2 pin must be
DATAP
DATAN
50 ?
(TO FLIP-FLOPS)
50 ?
V REG
R
R = 2.5k ? , DATA
R = 3k ? , CLK
400μA TYP
grounded and the monitor photodiode output must be
connected directly to the PSET pin.
DUAL MPD DWDM FUNCTION
(48-LEAD LFCSP ONLY)
Figure 10. AC Coupling of Data Inputs
For input signals that exceed 500 mV p-p single-ended, it is
necessary to insert an attenuation circuit as shown in Figure 11.
The ADN2847 has circuitry for a second monitor photodiode,
MPD2. The second photodiode current is mirrored to
IMPDMON2 for wavelength control purposes and is summed
internally with the first monitor photodiode current for the
R1
R2
R3
DATAP/CLKP
DATAN/CLKN
ADN2847
R IN
power control loop. For single MPD circuits, the MPD2 pin is
tied to GND.
This enables the system designer to use the two currents to
control the wavelength of the laser diode using various optical
filtering techniques inside the laser module.
If the monitor current functions IMPDMON and IMPDMON2
are not required, then the IMPD pin and IMPD2 pin can be
grounded and the monitor photodiode output can be connected
directly to PSET.
IDTONE (48-LEAD LFCSP ONLY)
The IDTONE pin is supplied for fiber identification/supervisory
channels or control purposes in WDM. This pin modulates the
optical one level over a possible range of 2% of minimum I MOD
to 10% of maximum I MOD . The level of modulation is set by con-
necting an external current sink between the IDTONE pin and
ground. There is a gain of two from this pin to the I MOD current.
Figure 12 shows how the AD9850/AD9851 or the AD9834 can
be used with the ADN2847 to allow fiber identification.
NOTES
1. R IN = 100 ? = THE DIFFERENTIAL INPUT
IMPEDANCE OF THE ADN2847.
Figure 11. Attenuation Circuit
CCBIAS
When the laser is used in ac-coupled mode, the CCBIAS pin
and the I BIAS pin should be tied together (Figure 15). In dc-
coupled mode, CCBIAS should be tied to V CC .
I BIAS
To achieve optimum eye quality, one pull-up resistor (R Z ) is
necessary, as shown in both circuits in Figure 14 and Figure 15.
The recommended resistor R Z value is approximately
200 Ω ~ 500 Ω.
AUTOMATIC LASER SHUTDOWN
The ADN2847 ALS allows compliance to ITU-T-G958 (11/94),
section 9.7. When ALS is logic high, both bias and modulation
currents are turned off. Correct operation of ALS can be confirmed
if the FAIL alarm is raised when ALS is asserted. Note that this
is the only time DEGRADE is low while FAIL is high.
Rev. B | Page 10 of 16
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