TECHNICAL NOTE TN007 ADN2841 EVALUATION This Technical Note
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Introduction:
TECHNICAL NOTE TN007
ADN2841 EVALUATION
This Technical Note describes ADN2841 laser diode driver evaluation kit. evaluation demonstration board that provides electrical evaluation ADN2841. This document describes configure board order operate part electrically. document contains following information: Board Description. Quick Start electrical operation. Description board settings. General Notes. Component List. Schematic board. Silkscreen Image board. Board Description: ADN2841 dual loop 155Mbs 2.7Gbps laser diode driver. board electrical configuration, current mirror circuit employed close average power extinction ratio control loops, thus takes place laser monitor diodes. Mirror gain related laser slope efficiency current. Resistors allow user modify gain current mirror such that used over full slope efficiency modulation current range. board initially setup divide bias current average modulation current thus producing simulated monitor photodiode current. Note that circuitry provided current mirror does simulate laser diode threshold current. Power, DEGRADE FAIL LEDs made available monitoring purposes. Power board only. Quick Start Electrical Operation: ensure proper operation electrical configuration, verify following: Jumper connected (shorted circuit). Jumpers connected Jumpers connected input data clocked necessary enable clock select (CLKSEL). CLKSEL enabled connecting clock inputs used, input data latched, connect Adjust R21, bias potentiometer, until combined series resistance roughly 1k2ohm.
REV.
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Information furnished Analog Devices believed accurate reliable. However, responsibility assumed Analog Devices use, infringements patents other rights third parties which result from use. license granted implication otherwise under patent patent rights Analog Devices.
REV. April 2001
TECHNICAL NOTE -HSN TN007
ADN2841 EVALUATION
Adjust R20, modulation potentiometer, until combined series resistance 3kohm. R19, alarm potentiometer, until combined series resistance 1kohm. Power board applying POWER input SMA. Apply differential signal, typically +/-500mV, (DATAN DATAP). clock select enabled apply differential clock signal, typically +/-500mV, (CLKN CLKP). electrical switching characteristics ADN2841 observed using digital communications analyser high-speed oscilloscope through connector Imodp output. bias modulation currents also monitored observing Ibmon Immon respectively. Ibmon Immon both 1:100 ratio Ibias Imod. Both terminated with resistors viewed Test Points using voltmeter oscilloscope. Ibias Imod will approximately 20mA 40mA respectively using resistance values given above combined with R32, combined with R33. change average power extinction ratio, following procedure. Adjust desired Ibias. Note that when increasing Ibias Imod, need first adjust such that current increases Ibias plus half increase intend make Imod. Then adjust desired Imod. This will also have effect returning Ibias intended value. take couple iterations adjust settings correctly. This dual control loop effect. important note that there threshold current adjustment this evaluation board therefore continually increasing modulation current, Imodn, result bias current, Ibias, falling zero. Ibias cannot negative. allowable resistance range Power Input (PSET), Extinction Ratio Input (ERSET), Alarm (ASET) between 1Kohm 25Kohm. Resistors R31-R33 ensure that resistance these nodes never falls below minimum allowable value. node resistances increase above 25Kohm ADN2841 will operate within specifications.
REV. April 2001
TECHNICAL NOTE -HSN TN007
ADN2841 EVALUATION
Description Board Settings: COMPONENT NAME POWER IMODP IDTONE CLKN CLKP DATAP DATAN IMPDMON IMPDMON2 IBMON IMMON ASET POTENTIOMETER ERSET POTENTIOMETER PSET POTENTIOMETER General Notes: bandwidth control loops will vary when PSET resistor current mirror gain varied. Your evaluation ADN2841 should cover range settings PSET resistor current mirror gain. This range should equivalent your expected range laser specifications power extinction ratio settings. important note that resistor values this evaluation board will support full slope efficiency range various lasers market. These resistor values need changed ensure current mirror adequate headroom operation maximum minimum Ibias Imod. FUNCTION power input board Imodp output. Connect scope. Idtone input. Clkn input. Clkp input. Datap input. Datan input. IMPD Current Mirror Output MPD2 Current Mirror Output Bias current mirror output Modulation current mirror output Adjusts bias current threshold disable fail alarms. Adjusts slope efficiency. Adjusts current thus average power. Jumper bypass supply protection diode. Jumper LBWSET Jumper exercise Jumper CLKSEL Jumper IDTONE
REV. April 2001
TECHNICAL NOTE -HSN TN007
ADN2841 EVALUATION
COMPONENT R19, R20, C4-C12 C13, R10, R16, R17, R31-R33 R11, R12, R13, R25, R26*, R27*, R28, K1-K5 J3-J7, DESCRIPTION trim potentiometer Supply Protection Diode (IN4001) LEDs 100nF capacitor 220uF capacitor capacitor (Loop Bandwidth Setting) Transistor (SOT23) 22uF capacitor resistor. resistor 51ohm resistor resistor resistor. 1kohm resistor. 1k5ohm resistor. resistor header jumper sockets connector. ADN2841 10nH inductor
*Signifies components which populated
REV. April 2001
TECHNICAL NOTE -HSN TN007
ADN2841 EVALUATION SCHEMATIC BOARD
REV. April 2001
TECHNICAL NOTE -HSN TN007
ADN2841 EVALUATION SILKSCREEN IMAGE BOARD
REV. April 2001
TECHNICAL NOTE -HSN TN007
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