|
|
PDF ADN2830 Data sheet ( Hoja de datos )
| Número de pieza | ADN2830 | |
| Descripción | Continuous Wave Laser Average Power Controller | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de ADN2830 (archivo pdf) en la parte inferior de esta página. Total 12 Páginas | ||
|
No Preview Available !
a
FEATURES
Bias Current Range 4 mA to 200 mA
Monitor Photodiode Current 50 A to 1200 A
Closed-Loop Control of Average Power
Laser FAIL and Laser DEGRADE Alarms
Automatic Laser Shutdown, ALS
Full Current Parameter Monitoring
5 V Operation
–40؇C to +85؇C Temperature Range
5 mm ؋ 5 mm 32-Lead LFCSP Package
APPLICATIONS
Fiber Optic Communication
Continuous Wave Laser
Average Power Controller
ADN2830
GENERAL DESCRIPTION
The ADN2830 provides closed-loop control of the average
optical power of a continuous wave (CW) laser diode (LD)
after initial factory setup. The control loop adjusts the laser
IBIAS to maintain a constant back facet monitor photodiode
(MPD) current and thus a constant laser optical power. The
external PSET resistor is adjusted during factory setup to set
the desired optical power. RPSET is set at 1.23/IAV, where IAV
is the MPD current corresponding to the desired optical power.
Programmable alarms are provided for laser fail (end of life)
and laser degrade (impending fail).
To provide monitoring of the MPD current, the MPD can be
connected to the IMPD pin. In this case, the MPD current is
mirrored to the IMPDMON pin to provide a monitor and
internally to the PSET pin to close the control loop.
By closing the feedback using IBMON rather than an MPD
connected to PSET, the device is configured to control a constant
current in the laser rather than a constant optical output power.
VCC
MPD
FUNCTIONAL BLOCK DIAGRAM
IBMON IMPDMON ALS FAIL DEGRADE MODE VCC GND
VCC
LD
IMPD
GND
PSET
RPSET
GND
CONTROL
PAVCAP
IBIAS
ASET
RASET
GND
GND
REV. A
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective companies.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703 © 2003 Analog Devices, Inc. All rights reserved.
1 page  
ADN2830
GENERAL
Laser diodes have current-in to light-out transfer functions as
shown in Figure 1. Two key characteristics of this transfer func-
tion are the threshold current, ITH, and slope in the linear region
beyond the threshold current, referred to as slope efficiency (LI).
⌬P
PAV
LI = ⌬P
⌬I ⌬ I
ITH CURRENT
Figure 1. Laser Transfer Function
CONTROL
A monitor photodiode (MPD) is required to control the laser
diode. The MPD current is fed into the ADN2830 to control
the power, continuously adjusting the bias current in response
to the laser’s changing threshold current and light to current
(LI) slope (slope efficiency).
The ADN2830 uses automatic power control (APC) to maintain
a constant power over time and temperature.
The average power is controlled by the RPSET resistor
connected between the PSET pin and ground. The PSET pin
is kept 1.23 V above GND. For an initial setup, the RPSET resis-
tor can be calculated using the following formula.
1.23 V
RPSET = I AV
where IAV is average MPD current.
Note the IPSET will change from device to device. It is not
required to know exact values for LI and MPD optical coupling.
LOOP BANDWIDTH SELECTION
Capacitor values greater than 22 nF are used to set the actual
loop bandwidth. This capacitor is placed between the PAVCAP
pin and ground. It is important that the capacitor is a low leak-
age multilayer ceramic with an insulation resistance greater than
100 GΩ or a time constant of 1000 sec, whichever is less.
ALARMS
The ADN2830 has two active high alarms, DEGRADE and
FAIL. A resistor between ground and the ASET pin is used to
set the current at which these alarms are raised. The current
through the ASET resistor is a ratio of (N ϫ 200):1 to the FAIL
alarm threshold (N is the number of ADN2830s in parallel).
The DEGRADE alarm will be raised at 90% of this level.
Example:
IFAIL = 50 mA, N = 1∴ IDEGRADE = 45 mA
I ASET
=
IBIASTRIP
N × 200
=
50 mA
200
= 250 µA
*RASET
= 1.23V
I ASET
=
1.23
250 µA
= 4.92 kΩ
The laser degrade alarm, DEGRADE, gives a warning of imminent
laser failure if the laser diode degrades further or environmental condi-
tions continue to stress the laser diode, e.g., increasing temperature.
The laser fail alarm, FAIL, is activated when:
• The ASET threshold is reached.
• The ALS pin is set high. This shuts off the modulation and
bias currents to the laser diode, resulting in the MPD current
dropping to zero.
DEGRADE will only be raised when the bias current exceeds
90% of the ASET current.
MONITOR CURRENTS
IBMON and IMPDMON are current controlled current sources
from VCC. They mirror the bias and MPD current for increased
monitoring functionality. An external resistor to GND gives a
voltage proportional to the current monitored. If the IMPDMON
function is not used, the IMPD pin must be grounded and the
monitor photodiode must be tied directly to the PSET pin.
AUTOMATIC LASER SHUTDOWN
When ALS is logic high, the bias current is turned off. Correct
operation of ALS can be confirmed by the fail alarm being
raised when ALS is asserted. Note that this is the only time
DEGRADE will be low while FAIL is high.
MODE
The MODE feature on the ADN2830 allows the user to operate
more than one ADN2830 in parallel current boosting mode to
achieve up to N ϫ 200 mA of bias current (N is the number of
ADN2830s in parallel). When using parallel boosting mode, one
device is run as the master, the other as the slave. The MODE
pin on the master is tied to ALS and the MODE pin on the
slave is tied high (see Figure 3 for reference circuit).
ALARM INTERFACES
The FAIL and DEGRADE outputs have an internal 30 kΩ
pull-up resistor that is used to pull the digital high value to VCC.
However, the alarm output may be overdriven with an external
resistor allowing the alarm interfacing to non-VCC levels.
Non-VCC alarm output levels must be below the VCC used for
the ADN2830.
*The smallest value for RASET is 1.2 kΩ, as this corresponds to the IBIAS
maximum of N ϫ 200 mA.
REV. A
–5–
5 Page 
–11–
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet ADN2830.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| ADN2830 | Continuous Wave Laser Average Power Controller | Analog Devices |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |