622Mbps, Low-Noise Transimpedance Preamplifier Optical Receivers

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622Mbps, Low-Noise Transimpedance Preamplifier Optical Receivers

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19-4765; 7/98
622Mbps, Low-Noise Transimpedance Preamplifier Optical Receivers
MAX3760 transimpedance preamplifier 622Mbps Aapplications. operates from single supply typically consumes only 100mW power. preamplifier converts small photodiode current differential voltage. cancellation circuit provides true differential output swing over wide range input current levels, thus reducing pulsewidth distortion. 6.5k transimpedance gain 560MHz bandwidth, combined with 73nA input-referred noise, provide -31.5dBm typical sensitivity 1300nm receivers. circuit accepts 1mAp-p input current, resulting typical optical overload -3dBm. device operates over extended temperature range -40°C +85°C. MAX3760 internally compensated requires external components. form includes space-saving filter connection, which provides positive bias photodiode through resistor VCC. These features, combined with aspect ratio dimensioning, allow MAX3760 assemble easily into TO-style header with photodiode. MAX3760 designed used with either MAX3761 MAX3762 limiting-amplifier ICs. When combined with photodiode, chipset forms complete 622Mbps receiver. MAX3760 available form 8-pin package.
ATION EVALU AVAILA
_Features
73nA Input-Referred Noise 560MHz Bandwidth Peak Input Current 6.5k Gain Operation from -40°C +85°C 100mW Typical Power Consumption Single Supply
MAX3760
Ordering Information
PART MAX3760ESA MAX3760E/D TEMP. RANGE -40°C +85°C -40°C +85°C PIN-PACKAGE Dice*
*Dice designed operate over -40°C +100°C junction temperature range, tested guaranteed +25°C.
_Applications
622Mbps ALAN Optical Receivers 622Mbps Optical Receivers
Typical Application Circuit
0.01µF (FILTER)
Configuration
VIEW
100pF INREF
MAX3760
0.01µF OUT+ (OPTIONAL) OUT-
MAX3761 MAX3762
LIMITING AMPLIFIER
COMP OUT+ OUTGND
COMP*
MAX3760
INREF
0.01µF
INDICATE PINS AVAILABLE ONLY DIE. *NOT CONNECTED
Maxim Integrated Products
free samples latest literature: http://www.maxim-ic.com, phone 1-800-998-8800 small orders, phone 408-737-7600 ext. 3468.
622Mbps, Low-Noise Transimpedance Preamplifier Optical Receivers MAX3760
ABSOLUTE MAXIMUM RATINGS
.-0.5V +7.0V Continuous Current FILTER .-5mA +5mA OUT+, OUT-.-25mA +25mA Voltage INREF .-0.5V +0.5V Voltage COMP.-0.5V (VCC 0.5V) Continuous Power Dissipation +85°C) (derate 5.88mW/°C above +85°C) .383mW Storage Temperature Range .-65°C +160°C Lead Temperature (soldering, 10sec) .+300°C Operating Junction Temperature Range (die) .-55°C +150°C Processing Temperature (die) .+400°C
Stresses beyond those listed under "Absolute Maximum Ratings" cause permanent damage device. These stress ratings only, functional operation device these other conditions beyond those indicated operational sections specifications implied. Exposure absolute maximum rating conditions extended periods affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC +4.5V +5.5V, COMP GND, load between OUT+ OUT-, -40°C +85°C, unless otherwise noted. Typical values +5.0V, +25°C.) (Note PARAMETER Input Bias Voltage Supply Current Small-Signal Transimpedance Output Common-Mode Level Differential Output Offset Output Impedance (per side) Maximum Differential Output Voltage FILTER Resistance Power-Supply Rejection Ratio ZOUT VOUT(MAX) RFILTER PSRR 1MHz, referred output 500µA, total peak-to-peak, differential signal 500µA, COMP open 1000 SYMBOL Input open Input open Differential output, input <10µA CONDITIONS 1200 0.95 UNITS
Note Dice tested +25°C.
ELECTRICAL CHARACTERISTICS
(VCC +4.5V +5.5V, COMP open, 0.75pF, outputs terminated differentially into 100, 8-pin package MAX3760 kit, +25°C, unless otherwise noted. Typical values +5V.) (Notes PARAMETER Small-Signal Bandwidth Low-Frequency Cutoff Pulse-Width Distortion Noise Referred Input Data-Dependent Jitter SYMBOL 20µA average input current (Note 0.75pF (Notes CONDITIONS 93.5 UNITS
Note characteristics guaranteed design characterization. Note source capacitance presented die. Includes package parasitic, photo diode, parasitic interconnect capacitance. Note Input 622Mbps pattern, signal amplitude 1mA, extinction ratio (re) Note Measured with 4-pole, 470MHz Bessel filter.
622Mbps, Low-Noise Transimpedance Preamplifier Optical Receivers
_Typical Operating Characteristics
(MAX3760 kit, +5.0V, COMP open, +25°C, unless otherwise noted.)
INPUT-REFERRED NOISE JUNCTION TEMPERATURE
MAX3760-01
MAX3760
SMALL-SIGNAL GAIN FREQUENCY
MAX3760-02
PULSE-WIDTH DISTORTION INPUT SIGNAL AMPLITUDE
622Mbps, ONE-ZERO PATTERN
MAX3760-03
INPUT-REFERRED NOISE (nA)
SOURCE CAPACITANCE PRESENTED DIE. INCLUDES PACKAGE PARASITIC, DIODE, PARASITIC INTERCONNECT CAPACITANCE 1.25pF 0.75pF 0.25pF
GAIN (dB)
(ps) 100k 100M
470MHz BANDWIDTH JUNCTION TEMPERATURE (°C)
FREQUENCY (Hz) 1000 INPUT SIGNAL AMPLITUDE (µAp-p)
INPUT-REFERRED NOISE CURRENT INPUT CURRENT
MAX3760toc04
TRANSIMPEDANCE AMBIENT TEMPERATURE
MAX3760-05
TYPICAL BANDWIDTH JUNCTION TEMPERATURE
TO-56 HEADER BANDWIDTH (MHz) 0.75pF SOURCE CAPACITANCE PRESENTED DIE. INCLUDES PACKAGE PARASITIC, DIODE, PARASITIC INTERCONNECT CAPACITANCE 1.25pF 0.25pF
MAX760toc06
INPUT-REFERRED NOISE (nA) 0.75pF 470MHz BANDWIDTH
7000
TRANSIMPEDANCE
6500
6000
5500
5000 1.00 2.15 4.64 10.0 21.5 46.4 1000 INPUT CURRENT (µA) AMBIENT TEMPERATURE (°C)
JUNCTION TEMPERATURE (°C)
TYPICAL EYEWIDTH INPUT SIGNAL
MAX3760 toc07
DATA-DEPENDENT JITTER INPUT SIGNAL AMPLITUDE
MAX3760-08
OUTPUT COMMON-MODE VOLTAGE AMBIENT TEMPERATURE
-1.2 -1.4 -1.6 REFERENCED
MAX3760-09
EYEWIDTH (ns) -40°C +85°C +25°C
PRBS 622Mbps
-1.0
JITTER
VOLTAGE 1000
-1.8 -2.0 -2.2 -2.4 -2.6 -2.8
INPUT SIGNAL (µA) INPUT SIGNAL AMPLITUDE (µAp-p)
-3.0 AMBIENT TEMPERATURE (°C)
622Mbps, Low-Noise Transimpedance Preamplifier Optical Receivers MAX3760
Typical Operating Characteristics (continued)
(MAX3760 kit, +5.0V, COMP open, +25°C, unless otherwise noted.)
MAXIMUM OUTPUT SIGNAL AMPLITUDE AMBIENT TEMPERATURE
OUTPUT SIGNAL AMPLITUDE (mVp-p)
MAX3760-10
AMBIENT TEMPERATURE (°C)
DIAGRAM (INPUT 10µA)
MAX3760-11
DIAGRAM (INPUT 1mA)
PRBS
MAX3760-12
50mV
500mV
PRBS
10mV/
100mV/
-50mV 200ps/div
-500mV 200ps/div
Description
NAME INREF OUTOUT+ COMP Supply-Voltage Input Signal Input Input Reference Connection. Connect photodetector ground. Ground Inverting Voltage Output. Current flowing into input causes OUT- decrease. Noninverting Voltage Output. Current flowing into input causes OUT+ increase. Compensation Capacitor Connection. Connection optional external compensation capacitor DCcancellation circuit. capacitance here reduce low-frequency cutoff cancellation circuit. Connect COMP directly disable cancellation circuit. Filter Connection. Provides positive bias photodiode through resistor (see Designing Filters section). Available only. FUNCTION
FILTER
622Mbps, Low-Noise Transimpedance Preamplifier Optical Receivers MAX3760
MAX3760
(FILTER)
TRANSIMPEDANCE AMPLIFIER INREF CANCELLATION AMPLIFIER OUT+ PARAPHASE OUT-
COMP
INDICATE PINS AVAILABLE ONLY.
Figure Functional Diagram
Detailed Description
MAX3760 transimpedance amplifier designed 622Mbps fiber optic applications. shown Functional Diagram (Figure comprises transimpedance amplifier, paraphase amplifier with emitterfollower outputs, cancellation circuit.
terminated with higher output impedances increased gain output voltage swing. MAX3760 will drive load ground. best noise rejection, terminate MAX3760 with differential loads.
Cancellation Circuit
cancellation circuit removes input signal's component employing low-frequency feedback. This feature centers input signal within transimpedance amplifier's dynamic range, thereby reducing pulse-width distortion large input signals. paraphase amplifier's output sensed through resistors then filtered, amplified, back base transistor transistor draws input signal's component away from transimpedance amplifier's summing node. MAX3760 cancellation loop internally compensated does require external capacitors most 622Mbps applications. external capacitance COMP reduce cancellation circuit's frequency response improve data-dependent jitter. Connecting COMP directly disables circuit. cancellation circuit sink input.
Transimpedance Amplifier
signal current input flows into high-gain amplifier's summing node. Shunt feedback through converts this current voltage with 6.5k gain. Diode clamps output voltage large input currents. INREF direct connection input transistor's emitter, must connected directly photodetector ground return best performance.
Paraphase Amplifier
paraphase amplifier converts single-ended signals differential signals introduces voltage gain This signal drives pair internally biased emitter followers, which form output stage. Resistors provide back-termination output, delivering differential output impedance. output emitter followers designed drive differential load between OUT+ OUT-. MAX3760 also
622Mbps, Low-Noise Transimpedance Preamplifier Optical Receivers MAX3760
MAX3760 minimizes pulse-width distortion data sequences exhibiting duty cycle. duty cycle significantly different from will cause MAX3760 generate pulse-width distortion. cancellation current drawn from input creates noise. This problem low-level signals with little component. Preamplifier noise increases signals with significant component (see Typical Operating Characteristics). MAX3760 operates with photodetector cathode connected VCC, shown Typical Application Circuit. Connecting photodetector anode cathode defeats cancellation circuit causes pulse-width distortion. Overload 10log 1000
Linear Range MAX3760 high gain, which limits output when input signal exceeds 20µAp-p. operates with linearity inputs exceeding following:
20µA 10log 1000
Input Reference
INREF reference point Connect close possible photodetector diode's ground. photodetector's ground usually ground photodetector's filter capacitor. total length from INREF, through filter capacitor diode, back input should more than 2cm.
Table Optical Power Relations
PARAMETER Average Power Extinction Ratio Optical Power Optical Power Signal Amplitude SYMBOL PAVE RELATION
PAVE 2PAVE
Applications Information
Optical Power Definitions
Many MAX3760's specifications relate input signal amplitude. When working with fiber optic receivers, optical input usually expressed terms average optical power extinction ratio. relations given Table convert optical power input signal when designing with MAX3760.
2PAVE 2PAVE
Note: Assuming average input duty cycle.
Calculating Sensitivity, Overload, Linear Range
Sensitivity Calculation MAX3760's input-referred noise current (in) generally dominates receiver sensitivity. system where error rate (BER) signal-tonoise ratio must always exceed 12.7. sensitivity, expressed average power, estimated
12.7in Sensitivity 10log 1000 2(re Where photodiode responsivity A/W.
OPTICAL POWER
PAVE
Input Overload overload largest input that MAX3760 accepts while meeting specifications. calculated
TIME
Figure Optical Power Definitions
622Mbps, Low-Noise Transimpedance Preamplifier Optical Receivers
Power Supply
MAX3760 operate from power-supply voltage (VCC GND) between 4.5V 5.5V. stable voltage, including -5.0V, found many systems using interface levels. supply-noise voltage divided between CFILTER CPHOTO. input noise current supply noise follows (assuming filter capacitor much larger than photodiode capacitance): INOISE
MAX3760
Layout Considerations
good high-frequency design layout techniques. multilayer circuit board with separate ground planes recommended. Take care bypass connect ground plane with shortest possible traces.
(VNOISE )(CPHOTO (RFILTER )(CFILTER
amount tolerable noise known, filter capacitor easy select, follows: CFILTER
Designing Low-Capacitance Input
Noise performance bandwidth will adversely affected stray capacitance Make every effort minimize capacitance this node. Select lowcapacitance photodiode good high-frequency design layout techniques. MAX3760 optimized 0.75pF capacitance input-approximately capacitance low-cost photodetector packaged header. When using MAX3760 package, note that package capacitance about 0.3pF. board between MAX3760 input photodetector will parasitic capacitance. Keep input line short, remove power ground planes beneath best possible performance, assemble MAX3760 form using chip-and-wire technology, package header. These techniques minimize parasitic capacitance, resulting lowest noise.
(VNOISE )(CPHOTO (RFILTER )(INOISE
example, with maximum noise voltage 10mVRMS, CPHOTO 0.75pF, RFILTER INOISE selected 30nA (half MAX3760's input noise): CFILTER
(10mV)(0.75pF) (1000)(30E
250pF
VIEW TO-56 HEADER
CFILTER
Designing Filters
MAX3760's noise performance strongly affected circuit's bandwidth, which changes over temperature varies from lot. Receiver sensitivity improved adding filters limit this bandwidth. Filter designs range from one-pole filter using single capacitor more complex filters using inductors. simple filter provides moderate rolloff with minimal components, while complex filter provides sharper rolloff better transient response. simple 530MHz filter created placing capacitor between OUT+ OUT- pins. Supply-voltage noise photodiode cathode produces current, PHOTO V/t, which reduces receiver sensitivity (CPHOTO photodiode capacitance.) MAX3760's FILTER resistor, combined with external capacitor, used reduce this noise (see Typical Application Circuit). Current generated
PHOTODIODE
OUT-
OUT+
CASE GROUND
Figure Suggested Layout TO-56 Header
622Mbps, Low-Noise Transimpedance Preamplifier Optical Receivers MAX3760
Wire Bonding
high current density reliable operation, MAX3760 uses gold metalization. Make connections with gold wire only, using ball-bonding techniques. Wedge bonding recommended. Die-pad size mils square, with pitch. thickness mils.
_Chip Topography
INREF FILTER
COMP
0.042" (1.05mm)
OUT-
OUT+
0.030" (0.75mm)
TRANSISTOR COUNT: SUBSTRATE CONNECTED
Package Information
SOICN.EPS

622Mbps, Low-Noise Transimpedance Preamplifier Optical Receivers

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