View MAX3260_80911.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

19-0322; Rev 0; 10/94
1GHz Transimpedance Preamplifier with 25dB Dynamic Range
_______________General Description
The MAX3260 high-speed transimpedance amplifier is ideally suited for Fibre Channel and SDH/SONET applications. An extended dynamic range makes the MAX3260 useful in optical receiver systems with as much as 25dB of input signal range. A DC-restore feedback network prevents amplifier saturation in all Fibre Channel applications by allowing input currents as high as 900A to be amplified linearly. To reduce noise, the restore function is disabled at low input levels, allowing detection of signals as small as 2.4A with a signal-tonoise ratio of 10. The filter output (FILTER) of the MAX3260 provides a convenient voltage source for a photodiode, especially when the circuit will be placed into a TO-style header with the photodiode. The filter output is connected to VCC through a 1k on-chip resistor. In combination with a bypass capacitor, the filter function significantly reduces the amount of noise present at the cathode of the photodiode. The MAX3260 operates from a single +5V supply consuming only 115mW of power when the output is AC coupled. With 50 output termination, it consumes less than 300mW of power.
____________________________Features
o 1GHz Bandwidth o Single 5V Supply o 25dB Dynamic Range o Optimized for TO-Style Header
MAX3260
______________Ordering Information
PART MAX3260C/D TJ RANGE 0C to +100C PIN-PACKAGE Dice
___________________Chip Topography
________________________Applications
High-Speed Fiber Optics 531Mbps and 1062Mbps Fibre Channel 622Mbps SDH/SONET Current-to-Voltage Converters PIN-Preamp Headers
VCCB 1
0.040" (1.016mm)
I IN 14
FILTER 13
N.C. 12
VOUT 11
10 GND
__________Typical Operating Circuit
VCCB 2
9 GND
VCCA 3
8 GND
DOUT+ LIMITING AMPLIFIER FILTER VOUT IIN MAX3260 VCC GND 50 Zo = 50 DINMAX3262 DOUT-
VCCA 4
7 GND
5 N.C.
0.040" (1.016mm)
6 GND
TRANSISTOR COUNT: 16
+5V
SUBSTRATE CONNECTED TO GND
________________________________________________________________ Maxim Integrated Products 1
Call toll free 1-800-998-8800 for free samples or literature.
1GHz Transimpedance Preamplifier with 25dB Dynamic Range MAX3260
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VCCA, VCCB to GND ...............................0V, 6V Input Current, IIN, FILTER ..................................................1.5mA Input Bias Voltage, VIN ......................................................0V, 6V Output Voltage, VOUT ........................................................0V, 6V Operating Junction Temperature Range ...........-55C to +150C Processing Temperature..................................................+400C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC = +5V, output terminated with 50 to ground, 100% tested, TJ = +27C, unless otherwise noted.) PARAMETER DC SPECIFICATIONS PARAMETER Input Bias Voltage DC-Restore Time Constant Filter Resistor Value Supply Current DC Transimpedance SYMBOL SYMBOL VIN tDC RFILTER IVCC CONDITIONS CONDITIONS MIN MIN TYP TYP 1.6 1 56 -400 -2400 -2000 350 -2400 0.8 -2000 1.0 -1600 900 100 240 21 3 -1600 MAX MAX UNITS UNITS V s mA V/A A V/A GHz A ps nA dB
750 50 load to ground IIN > 400A IIN < 100A
1250 70
DC-Restore Activation Current IRESTORE AC SPECIFICATIONS (Not production tested) Small-Signal Transimpedance GT -3dB Bandwidth BWU Peak Input Current IIN Pulse-Width Distortion PWD (Notes 1, 2, 3) Input Referred Current Noise INRMS (Notes 2, 4) Power-Supply Rejection Ratio PSRR Output Resistance ROUT Note 1: Note 2: Note 3: Note 4:
Input is a square wave with 0.5GHz frequency and <200ps rise time. External capacitance on the input 0.4pF. Pulse-width distortion measured at the 50% level of the output pulses: Input is 900A, zero-peak. Output noise is measured through a four-pole Bessel filter with -3dB bandwidth of 800MHz. Noise is then referred to the input by dividing the DC transimpedance.
__________________________________________Typical Operating Characteristics
(TJ = +27C, unless otherwise noted.)
FREQUENCY RESPONSE
MAX3260-01
DC TRANSFER FUNCTION
1.8 1.6 1.4 VOUT (V) 1.2 1.0 0.8 0.6 0.4 0.2 0
MAX3260-03
68 67 66 VOUT/IIN GAIN (dB) 65 64 63 62 61 60 59 58 0 200 400 600
2.0
800 1000 1200 1400
0
200
400
600
800
1000
FREQUENCY (MHz)
IIN (A)
2
_______________________________________________________________________________________
1GHz Transimpedance Preamplifier with 25dB Dynamic Range
____________________________Typical Operating Characteristics (continued)
(TJ = +27C, unless otherwise noted.)
EYE DIAGRAM 1Gbps
MAX3260-4
MAX3260
SUPPLY CURRENT vs. TEMPERATURE (OUTPUT AC COUPLED)
28 SUPPLY CUREENT (mA) 26 24 22 20 18 16 14 4.75V 5.25V 5.0V
MAX3260-TOC5
2.0905V
30
100mV/div 1.0905V 37.98ns
0
20
40
60
80
100
250ps/div
40.48ns
TEMPERATURE (C)
_______________Detailed Description
The MAX3260 is a high-speed transimpedance amplifier, designed to accomodate input currents with a large dynamic range. This circuit is optimized to operate in a 1062Mbps Fibre Channel reciever, and is also suitable for use in 622Mbps SONET applications. The MAX3260 employs shunt-shunt feedback around a bipolar amplifier. The resulting circuit provides an inverted current-to-voltage conversion. The conversion gain is nominally -2000V/A. Modern fiber-optic communications systems place many requirements on transimpedance preamplifiers. Power budgets are important when considering a preamp, since the circuit will generally be placed into a small module or header, which limits the amount of heat dissipation. In addition, the signal presented to the preamp may carry an 18dB to 20dB dynamic range, which must be amplified linearly to prevent the addition of jitter. Finally, preamp noise generally determines the receiver sensitivity, and must be held to a minimum. The MAX3260 employs several techniques to address the needs of fiber-optic preamplifiers. The output of the MAX3260 operates in the 1V to 2V range (depending
on the average input) to keep output standing current at a minimum. The reduced output voltage helps keep power consumption low, but also reduces the dynamic range of the output stage. Fiber communications transimpedance amplifiers commonly use dynamic control of the shunt-shunt feedback loop to vary the gain. The unwanted side-effect of this technique is a circuit bandwidth that varies with input current. To prevent outputstage saturation, the MAX3260 employs a DC-restore circuit. As input signal power increases, DC current is drawn away from the input node of the amplifier. This reduces the DC gain of the amplifier without affecting the small-signal performance. To prevent noise feedback at low signals, an integrated comparator senses the power level and disables the DC-restore function. The MAX3260's filter output provides a convenient voltage source for a photodiode, especially when the circuit will be placed into a TO-style header with the photodiode. The filter output is connected to V CC through an on-chip 1k resistor. In combination with a bypass capacitor, the filter function reduces the bandwidth at the anode of the photodiode, therefore significantly reducing the amount of noise at the cathode. The filter connection can be left unconnected if not used.
_______________________________________________________________________________________
3
1GHz Transimpedance Preamplifier with 25dB Dynamic Range MAX3260
VCCA VCCB
1k FILTER 2.5k 4k VCCA IIN COMPARATOR 1.6V DC RESTORE CIRCUIT VOUT
VCCA
MAX3260
Figure 1. Functional Diagram
_______________________Wire Bonding
For high current density and reliable operation, the MAX3260 uses gold metallization. Connections to the die should be made with gold wire only, using ball bonding techniques. Wegde bonding is not recommended. Die pad size is 4 mils.
The MAX3260 will typically be connected to a limiting or post amplifier by means of a controlled-impedance transmission line. If a transmission line is used, it is important to end-terminate the line with the characteristic impedance to prevent reflections into the output of the MAX3260.
__________________Design Procedure
The MAX3260 is a high-speed, high-gain component. Its performance is strongly affected by module design and layout. Improper design techniques can cause oscillations or ringing. In fiber-optic receiver applications, it is highly recommended that the transimpedance preamplifier be placed close to the photodetector, in the same package or header if possible. This reduces parasitic inductance and improves static-discharge protection during manufacturing. An alternative layout is to assemble the preamplifier on a hybrid circuit board. In either case, the designer should ensure that power-supply runs to the VCCA and VCCB inputs are properly filtered. Keep ground connections to the MAX3260 short and minimize inductance. Multiple vias may be required when connecting to the ground plane on a circuit board, to reduce the ground inductance.
__________Applications Information
The MAX3260 consumes approximately 23mA of current with no output load. Typically, the majority of power used by the preamplifier is consumed in the output termination. The termination is needed at the end of the transmission line connecting MAX3260 to a limiting amplifer. The average output level is typically 1.6V, and is maintained at that level by the DC-restore function. A 50 termination to ground will consume 32mA of standing current. Power consumption can be reduced by terminating to higher resistance. A 75 transmission line and termination would consume only 22mA. Power consumption can be reduced dramatically by excluding the transmission line and termination, which requires very short distances between the MAX3260 and the following circuit.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
4 ___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 (c) 1994 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

▲Up To Search▲

Price & Availability of MAX3260

	To Download MAX3260 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .