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19-1523; Rev 1; 1/00
3.0V to 5.5V, 1.25Gbps/2.5Gbps Limiting Amplifiers
General Description
The 1.25Gbps MAX3264/MAX3268 and the 2.5Gbps MAX3265/MAX3269 limiting amplifiers are designed for Gigabit Ethernet and Fibre Channel optical receiver systems. The amplifiers accept a wide range of input voltages and provide constant-level output voltages with controlled edge speeds. Additional features include RMS power detectors with programmable loss-of-signal (LOS) indication, an optional squelch function that mutes the data output signal when the input voltage falls below a programmable threshold, and excellent jitter performance. The MAX3264/MAX3265 feature current-mode logic (CML) data outputs that are tolerant of inductive connectors and a 16-pin TSSOP package, making these circuits ideal for GBIC receivers. The MAX3268/ MAX3269 feature standards-compliant positive-referenced emitter-coupled logic (PECL) data outputs and are available in a tiny 10-pin MAX package that is ideal for small-form-factor receivers. o +3.0V to +5.5V Supply Voltage o Low Deterministic Jitter 14ps (MAX3264) 11ps (MAX3265) o 150ps max Edge Speed (MAX3265) 300ps max Edge Speed (MAX3264) o Programmable Signal-Detect Function o Choice of CML or PECL Output Interface o 10-Pin MAX or 16-Pin TSSOP Package
Features
MAX3264/MAX3265/MAX3268/MAX3269
Ordering Information
PART MAX3264CUE MAX3264C/D MAX3265CUE MAX3265CUB MAX3265C/D MAX3265EUE MAX3268CUB MAX3268C/D MAX3269CUB MAX3269C/D TEMP. RANGE 0C to +70C 0C to +70C 0C to +70C 0C to +70C 0C to +70C -40C to +85C 0C to +70C 0C to +70C 0C to +70C 0C to +70C PIN-PACKAGE 16 TSSOP-EP Dice* 16 TSSOP-EP 10 MAX-EP Dice* 16 TSSOP-EP 10 MAX-EP Dice* 10 MAX-EP Dice*
Applications
Gigabit Ethernet Optical Receivers Fibre Channel Optical Receivers System Interconnect ATM Optical Receivers
Selector Guide appears at end of data sheet. Pin Configurations appear at end of data sheet.
*Dice are designed to operate from 0C to +70C, but are tested and guaranteed only at TA = +25C. EP = Exposed paddle
Typical Operating Circuits
CAZ VCC
VCC
CAZ1
CAZ2
VCC
CIN 0.01F IN+ 100 IN-
MAX3264CUE MAX3265CUE MAX3265EUE
OUT+
RTERM 0.01F
OUT-
0.01F
RL 100
MAX3266 MAX3267
CIN 0.01F TH SQUELCH LOS LOS LEVEL VCC RTH N.C. LOSS N.C. OF SIGNAL N.C.
RTERM
Typical Operating Circuits continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
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3.0V to 5.5V, 1.25Gbps/2.5Gbps Limiting Amplifiers MAX3264/MAX3265/MAX3268/MAX3269
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VCC) ............................................-0.5V to +6.0V Voltage at IN+, IN- ..........................(VCC - 2.4V) to (VCC + 0.5V) Voltage at SQUELCH, CAZ1, CAZ2, LOS, LOS, TH..................................-0.5V to (VCC + 0.5V) Voltage at LEVEL...................................................-0.5V to +2.0V Current into LOS, LOS ..........................................-1mA to +9mA Differential Input Voltage (IN+ - IN-) .....................................2.5V Continuous Current at CML Outputs (OUT+, OUT-) ..........................-25mA to +25mA Continuous Current at PECL Outputs (OUT+, OUT-) .........50mA Continuous Power Dissipation (TA = +70C) 16-Pin TSSOP (derate 27mW/C above +70C) .........2162mW 10-Pin MAX (derate 20mW/C above +70C) ...........1600mW Operating Ambient Temperature Range .............-40C to +85C Storage Temperature Range .............................-55C to +150C Processing Temperature (dice) .......................................+400C Lead Temperature (soldering, 10s) .................................+300C
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
(Data outputs terminated per Figure 1, VCC = +3.0V to +5.5V, TA = 0C to +70C. Typical values are at VCC = +3.3V, TA = +25C, unless otherwise noted.) (Note 1) PARAMETER Data Rate Input Voltage Range Deterministic Jitter Random Jitter MAX3264/MAX3268 MAX3265/MAX3269 MAX3264/MAX3268 MAX3265/MAX3269 MAX3264/MAX3268 (Notes 2, 3) MAX3265/MAX3269 (Notes 2, 3) MAX3264/MAX3268 (Notes 2, 4) MAX3265/MAX3269 (Notes 2, 4) MAX3264 (Note 5) Data Output Edge Speed MAX3265 (Note 6) MAX3268 (Note 5) MAX3269 (Note 6) LOS Hysteresis LOS Assert/Deassert Time Low LOS Assert Level Low LOS Deassert Level (Notes 2, 7) (Notes 7, 8) RTH = 2.5k RTH = 2.5k MAX3264/MAX3268 MAX3265/MAX3269 MAX3264/MAX3268 MAX3265/MAX3269 1.20 2.20 2.5 80 80 5 10 14 11 15 8 175 100 150 100 4.4 1 2.6 4.8 4.5 8.5 6.9 12.2 300 150 300 150 dB s mV mV ps CONDITIONS MIN TYP 1.25 2.5 1200 1200 30 25 MAX UNITS Gbps mV psp-p psRMS
2
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3.0V to 5.5V, 1.25Gbps/2.5Gbps Limiting Amplifiers
ELECTRICAL CHARACTERISTICS (continued)
(Data outputs terminated per Figure 1, VCC = +3.0V to +5.5V, TA = 0C to +70C. Typical values are at VCC = +3.3V, TA = +25C, unless otherwise noted.) (Note 1) PARAMETER Medium LOS Assert Level Medium LOS Deassert Level High LOS Assert Level High LOS Deassert Level Squelch Input Current Differential Input Resistance Input-Referred Noise CML Output Voltage PECL Output High Voltage PECL Output Low Voltage LOS Output High Voltage LOS Output Low Voltage Output Signal When Squelched Power-Supply Rejection Ratio Low-Frequency Cutoff Output Resistance (single ended) IN+ to INMAX3264/MAX3268 MAX3265/MAX3269 LEVEL = open, RLOAD = 50 LEVEL = GND and RLOAD = 75 Referenced to VCC Referenced to VCC ILOS = -30A ILOS = +1.2mA Outputs AC-coupled f < 2MHz CAZ = open CAZ = 0.1F MAX3264/MAX3265 MAX3268/MAX3269 MAX3264 Power-Supply Current Figure 2 MAX3265 MAX3268 MAX3269 85 20 20 2 2 100 4 38 50 39 48 62 76 62 78 mA 115 550 1100 -1.025 -1-810 2.4 0.4 1270 RTH = 7k RTH = 7k RTH = 20k RTH = 20k CONDITIONS MAX3264/MAX3268 MAX3265/MAX3269 MAX3264/MAX3268 MAX3265/MAX3269 MAX3264/MAX3268 MAX3265/MAX3269 MAX3264/MAX3268 MAX3265/MAX3269 0 97 9.4 18.0 MIN 5.6 9.9 TYP 9 1.6 15 27 21.6 41.5 35 67 80 100 150 230 1200 1800 -0.880 1.620 53.0 101 400 103 19.8 35.0 MAX UNITS mV mV mV mV A VRMS mV V V V V mV dB MHz kHz
MAX3264/MAX3265/MAX3268/MAX3269
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3.0V to 5.5V, 1.25Gbps/2.5Gbps Limiting Amplifiers MAX3264/MAX3265/MAX3268/MAX3269
ELECTRICAL CHARACTERISTICS--MAX3265EUE
(Data outputs terminated per Figure 1, VCC = +3.0V to +5.5V, TA = -40C to +85C. Typical values are at VCC = +3.3V, TA = +25C, unless otherwise noted.) (Note 1) PARAMETER Data Rate Input Voltage Range Deterministic Jitter Random Jitter Data Output Edge Speed LOS Hysteresis LOS Assert/Deassert Time Low LOS Assert Level Low LOS Deassert Level Medium LOS Assert Level Medium LOS Deassert Level High LOS Assert Level High LOS Deassert Level Squelch Input Current Differential Input Resistance Input-Referred Noise CML Output Voltage LOS Output High Voltage LOS Output Low Voltage Output Signal When Squelched Power-Supply Rejection Ratio Low-Frequency Cutoff Output Resistance (single ended) Power-Supply Current Figure 2 LEVEL = open, RLOAD = 50 LEVEL = GND, RLOAD = 75 ILOS = -30A ILOS = +1.2mA Outputs AC-coupled f < 2MHz CAZ = open CAZ = 0.1F 85 20 20 2 2 100 50 115 76 550 1100 2.4 0.450 1270 IN+ to IN(Notes 2, 3) (Notes 2, 4) (Note 6) (Notes 2, 7) (Notes 7, 8) RTH = 2.5k RTH = 2.5k RTH = 7k RTH = 7k RTH = 20k RTH = 20k 0 97 18.0 9.9 2.20 2.2 10 11 8 100 4.4 1 4.8 8.5 16 27 41.5 67 80 100 230 1200 1800 111 400 103 43.0 13.6 155 CONDITIONS MIN TYP 2.5 1200 25 MAX UNITS Gbps mV psp-p psRMS ps dB s mV mV mV mV mV mV A VRMS mV V V mV dB MHz kHz mA
Note 1: Specifications for Input Voltage Range, LOS Assert/Deassert Levels, and CML Output Voltage refer to the total differential peak-to-peak signal applied or measured. PECL output voltages are absolute (single-ended) voltages measured at a single output. Note 2: Input edge speed is controlled using 4-pole, lowpass Bessel filters with bandwidth approximately 75% of the maximum data rate. Note 3: Deterministic jitter is measured with a K28.5 pattern (0011 1110 1011 0000 0101). Deterministic jitter is the peak-to-peak deviation from ideal time crossings, measured at the zero-level crossings of the differential output per ANSI X3.230, Annex A. Note 4: Random jitter is measured with the minimum input signal applied after filtering with a 4-pole, lowpass, Bessel filter (frequency bandwidth at 75% of the maximum data rate). For Fibre Channel and Gigabit Ethernet applications, the peak-to-peak random jitter is 14.1-times the RMS random jitter. Note 5: Input signal applied after a 933MHz Bessel filter. Note 6: Input signal applied after a 1.8GHz Bessel filter. Note 7: Input for LOS assert/deassert and hysteresis tests is a repeating K28.5 pattern. Hysteresis is defined as: 20log (VLOS-DEASSERT / VLOS-ASSERT). Note 8: Response time to a 10dB change in input power. 4 _______________________________________________________________________________________
3.0V to 5.5V, 1.25Gbps/2.5Gbps Limiting Amplifiers
Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
MAX3264/MAX3265/MAX3268/MAX3269
OUTPUT VOLTAGE vs. INPUT VOLTAGE
MAX3264/5/8/9 TOC01a
MAX3264 LOS HYSTERESIS vs. TEMPERATURE
MAX3264/5/8/9 TOC03a
MAX3265EUE LOS HYSTERESIS vs. TEMPERATURE
MAX3264/5/8/9 TOC03
1700 1500 OUTPUT VOLTAGE (mV) MAX3264/MAX3268 1300 1100 MAX3265/MAX3269 900 700 500 300 0 2 4 6 8 10
6.5 6.0 LOS HYSTERESIS (dB) 5.5 5.0 RTH = 7k 4.5 4.0 3.5 RTH = 25k
6.5 6.0 LOS HYSTERESIS (dB) 5.5 5.0 4.5 4.0 3.5 RTH = 16k RTH = 4.6k
12
0
10
20
30
40
50
60
70
-40
-15
10
35
60
85
INPUT VOLTAGE (mV)
TEMPERATURE (C)
TEMPERATURE (C)
MAX3264/MAX3268 DETERMINISTIC JITTER vs. INPUT AMPLITUDE
MAX3264/5/8/9 TOC04
MAX3264/MAX3268 RANDOM JITTER vs. INPUT AMPLITUDE
14 12 RMS JITTER (ps) 10 8 6 4
MAX3264/5/8/9 TOC05
MAX3265/MAX3269 DETERMINISTIC JITTER vs. INPUT AMPLITUDE
MAX3264/5/8/9 TOC06
30 25 20 JITTER (ps) 15 10 5 0 0 200 400 600 800 1000
16
30 25 20 JITTER (ps) 15 10 5 0
2 0 1200 0 10 20 30 40 50 INPUT AMPLITUDE (mV) INPUT AMPLITUDE (mV)
0
200
400
600
800
1000
1200
INPUT AMPLITUDE (mV)
MAX3265/MAX3269 RANDOM JITTER vs. INPUT AMPLITUDE
MAX3264/5/8/9 TOC07
LOSS OF SIGNAL WITH SQUELCH
MAX3264/5/8/9 TOC08
MAX3268 DATA OUTPUT EYE DIAGRAM (MINIMUM INPUT)
MAX3264/5/8/9 TOC09
8 7 6 RMS JITTER (ps) 5 4 3 2 1 0 0 10 20 30 40
VIN
VOUT 300mV/div VLOS
50
500ns/div
200ps/div
INPUT AMPLITUDE (mV)
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3.0V to 5.5V, 1.25Gbps/2.5Gbps Limiting Amplifiers MAX3264/MAX3265/MAX3268/MAX3269
Typical Operating Characteristics (continued)
(TA = +25C, unless otherwise noted.)
MAX3264 DATA OUTPUT EYE DIAGRAM AT 1.25Gbps (MINIMUM INPUT)
MAX3264/5/8/9 TOC10
MAX3264 DATA OUTPUT EYE DIAGRAM AT 1.25Gbps (MAXIMUM INPUT)
MAX3264/5/8/9 TOC11
MAX3265 DATA OUTPUT EYE DIAGRAM 2.5Gbps (MINIMUM INPUT)
MAX3264/5/8/9 TOC12
150mV/div
50mV/div
150mV/div
200ps/div
200ps/div
100ps/div
MAX3265 DATA OUTPUT EYE DIAGRAM 2.5Gbps (MAXIMUM INPUT)
MAX3264/5/8/9 TOC13
POWER-SUPPLY REJECTION RATIO vs. FREQUENCY
25 20 PSRR (dB) 15 10 5 0
MAX3264/5/8/9 TOC14
OUTPUT VSWR vs. FREQUENCY
MAX3264/5/8/9 TOC15
4.0 3.5 3.0 VSWR 2.5 2.0 1.5 1.0
150mV/div
100ps/div
100k
1M
10M FREQUENCY (Hz)
100M
1G
0
0.5
1.0
1.5
2.0
2.5
3.0
FREQUENCY (GHz)
MAX3264 LOSS-OF-SIGNAL THRESHOLD vs. RTH
MAX3264/5/8/9 TOC18
MAX3265 LOSS-OF-SIGNAL THRESHOLD vs. RTH
MAX3264/5/8/9 TOC19
COMMON-MODE REJECTION RATIO vs. FREQUENCY
50 45 40 CMRR (dB) 35 30 25 20 15 10 MAX3265 MAX3268
MAX3264/5/8/9 TOC20
40 35 LOS ASSERT THRESHOLD (mV) 30 25 20 15 10 5 0 0 5 10 15 20 RTH (k) 25 30
60 50 40 30 20 10 0
55
LOS ASSERT THRESHOLD (mV)
5 0 5 10 15 RTH (k) 20 25 30 1M 10M 100M FREQUENCY (Hz) 1G 10G
35
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3.0V to 5.5V, 1.25Gbps/2.5Gbps Limiting Amplifiers
Pin Description
PIN NAME MAX 1, 4 2 3 5 TSSOP 3, 6 4 5 8 GND IN+ INTH Supply Ground Noninverted Input Signal Inverted Input Signal Loss-of-Signal Threshold. A resistor connected from this pin to ground sets the input signal level at which the loss-of-signal (LOS) output(s) will be asserted. Refer to Typical Operating Characteristics and Design Procedure. Inverted Loss-of-Signal Output. LOS is high when the level of the input signal is above the preset threshold set by the TH input. LOS is asserted low when the signal level drops below the threshold. Supply Voltage Inverted Data Output Noninverted Data Output Offset-Correction-Loop Capacitor. A capacitor connected between this pin and CAZ2 extends the time constant of the offset correction loop. Offset-Correction-Loop Capacitor. A capacitor connected between this pin and CAZ1 extends the time constant of the offset correction loop. Refer to Design Procedure. Output Current Level. When this pin is not connected, the CML output current is approximately 16mA. When this pin is connected to ground, the output current increases to approximately 20mA. (In the MAX3265CUB, LEVEL is internally connected to ground.) Noninverted Loss-of-Signal Output. LOS is low when the level of the input signal is above the preset threshold set by the TH input. LOS asserts high when the signal level drops below the threshold. Squelch Input. The squelch function is disabled when SQUELCH is not connected or is set to a TTL-low level. When SQUELCH is set to a TTL-high level and LOS is asserted, the data outputs, OUT+, and OUT-, are forced to static levels. See sections PECL Output Buffer and CML Output Buffer for more information. (In the 10pin MAX, SQUELCH is not connected.) No Connection Ground. The exposed paddle must be soldered to the circuit-board ground for proper thermal performance. FUNCTION
MAX3264/MAX3265/MAX3268/MAX3269
6 7, 10 8 9 --
9 11, 14 12 13 1
LOS VCC OUTOUT+ CAZ1
--
2
CAZ2
--
7
LEVEL
--
10
LOS
--
15
SQUELCH
-- EP
16 EP
N.C. Exposed Paddle
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3.0V to 5.5V, 1.25Gbps/2.5Gbps Limiting Amplifiers MAX3264/MAX3265/MAX3268/MAX3269
VCC VCC VCC VCC 100 100 100 RTERM 100 COUT 2 x RLOAD 100 100 100 300 RTERM 300 COUT 2 x RLOAD 150
COUT
COUT
MAX3264 MAX3265 (a) MAX3264/MAX3265 WITH 50 TERMINATION VCC
MAX3264 MAX3265 (b) MAX3264/MAX3265 WITH 75 TERMINATION
MAX3268 MAX3269
OUTOUT+
50
RTERM 50
(c) MAX3268/MAX3269 OUTPUT TERMINATION
VCC - 2V
Figure 1. Data Output Termination
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3.0V to 5.5V, 1.25Gbps/2.5Gbps Limiting Amplifiers MAX3264/MAX3265/MAX3268/MAX3269
VCC
ICC IOUT 100 100
SQUELCH (OPEN) CONTROL MAX3264 MAX3265 LEVEL (OPEN) MAX3264CUE: OPEN MAX3265CUE: OPEN MAX3265CUB: GND
RTH 2.5k
(a) CML SUPPLY CURRENT (ICC)
VCC
ICC
OUT+
OPEN
MAX3268 MAX3269
OUTOPEN RTH 2.5k
(b) PECL SUPPLY CURRENT (ICC)
Figure 2. Power-Supply Current Measurement _______________________________________________________________________________________ 9
3.0V to 5.5V, 1.25Gbps/2.5Gbps Limiting Amplifiers MAX3264/MAX3265/MAX3268/MAX3269
_______________Detailed Description
Figure 3 is a functional diagram of the MAX3264/ MAX3265/MAX3268/MAX3269 limiting amplifiers. A linear input buffer drives a multistage limiting amplifier and an RMS power detection circuit. Offset correction with lowpass filtering ensures low deterministic jitter. The output buffer produces a limited output signal. The MAX3264/MAX3265 produce a CML output, while the MAX3268/MAX3269 produce a PECL-compatible output signal. Schematics of these input/output circuits are shown in Figures 4 through 7.
RMS Power Detect with Loss-of-Signal Indicator
An RMS power detector looks at the signal from the input buffer and compares it to a threshold set by the TH resistor (see Typical Operating Characteristics for appropriate resistor values). The signal-detect information is provided to the LOS outputs, which are internally terminated with 8k (MAX3265/MAX3269) or 16k (MAX3264/MAX3268) pull-up resistors. The LOS outputs meet TTL voltage specifications when loaded with a resistor 4.7k.
TH VCC
MAX3264 MAX3265 MAX3268 MAX3269
POWER DETECT WITH COMPARATOR
RLOS = 8k (MAX3265/MAX3269) RLOS = 16k (MAX3264/MAX3268) RLOS TTL VCC LOS
RLOS TTL LOS
IN+ 100 ININPUT BUFFER
GAIN OUT+ OUTPUT BUFFER OUT-
SQUELCH LOWPASS OFFSET CORRECTION 100pF CONTROL LEVEL
CAZ1 TOTAL GAIN = 55dB (MAX3264/MAX3268) TOTAL GAIN = 49dB (MAX3265/MAX3269)
CAZ2
Figure 3. Functional Diagram
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3.0V to 5.5V, 1.25Gbps/2.5Gbps Limiting Amplifiers
Input Buffer
The input buffer is designed to accept input signals from the MAX3266/MAX3267 transimpedance amplifiers. The input buffer provides a 100 input impedance between IN+ and IN-. Input VSWR is typically less than 2.0 for frequencies less than 2GHz. DC-coupling the inputs is not recommended; this prevents the DC offset-correction circuitry from functioning properly.
CML Output Buffer
The MAX3264/MAX3265 CML output circuits (Figure 7) provide high tolerance to impedance mismatches and inductive connectors. The output current can be set to two levels. When the LEVEL pin is left unconnected, output current is approximately 16mA. Connecting LEVEL to ground sets the output current to approximately 20mA. The squelch function is enabled when the SQUELCH pin is set to a TTL-high level or connected to VCC. The squelch function holds OUT+ and OUT- at a static voltage whenever the input signal power drops below the loss-of-signal threshold. In the 10-pin MAX package, SQUELCH is left internally unconnected. SQUELCH operation is described in Table 1. The buffer's output impedance is determined by the parallel combination of internal and external pull-up resistors, which are chosen to match the impedance of the transmission line (Figure 1). The output buffer can be AC- or DC-coupled to the load.
MAX3264/MAX3265/MAX3268/MAX3269
Gain Stage and Offset Correction
The limiting amplifier provides approximately 55dB (MAX3264/MAX3268) or 49dB (MAX3265/MAX3269) of gain. This large gain makes the amplifier susceptible to small DC offsets in the input signal. DC offsets as low as 1mV will reduce the accuracy of the power detection circuit and may cause deterministic jitter. A low-frequency feedback loop is integrated into the limiting amplifier to reduce input offset, typically to less than 100V. An external capacitor connected between CAZ1 and CAZ2, in parallel with internal capacitance, determines the time constant of the offset-correction circuit. The offset-correction circuit requires an average data-input mark density of 50% to prevent an increase in dutycycle distortion and to ensure low deterministic jitter.
Table 1. Squelch Operation
LEVEL PIN Open VCC VOLTAGE WHEN SQUELCHED OUTVCC - 100mV VCC - 100mV OUT+ VCC VCC - 100mV
Internal Input/Output Schematics
VCC
VCC 500 0.25pF IN+ 110 IN0.25pF LOS RT 500
ESD STRUCTURES
ESD STRUCTURE
GND RT = 8k (MAX3265/MAX3269) RT = 16k (MAX3264/MAX3268) GND
Figure 4. Input Circuit
Figure 5. LOS Output Circuit 11
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3.0V to 5.5V, 1.25Gbps/2.5Gbps Limiting Amplifiers MAX3264/MAX3265/MAX3268/MAX3269
VCC VCC ESD STRUCTURES ESD STRUCTURES 100 100 OUT+ OUTOUT+ OUT-
GND
GND
LEVEL
Figure 6. PECL Output Circuit
Figure 7. CML Output Circuit
PECL Output Buffer
The MAX3268/MAX3269 offer an industry-standard PECL output. The PECL outputs should be terminated to VCC - 2V. Figure 6 shows the PECL output circuit. The squelch function forces OUT+ to a high level and OUT- to a low level when the input is below the programmed LOS threshold. In the 10-pin MAX, SQUELCH is left unconnected.
For Fibre Channel, Gigabit Ethernet, or other applications using 8B/10B data coding, select (CIN, COUT) 0.01F, which provides fIN < 320kHz. For ATM/SONET or other applications using scrambled NRZ data, select (CIN, COUT) 0.1F, which provides fIN < 32kHz.
Select the Offset-Correction Capacitor (MAX3264/MAX3265 only)
To maintain stability, it is important to keep a onedecade separation between fIN and the low-frequency cutoff (fOC) associated with the DC-offset-correction circuit. fOC = 75 / [2 60k (CAZ + 100pF)] = 200 * 10 -6 / (CAZ + 100pF) For Fibre Channel, Gigabit Ethernet, or other applications using 8B/10B data coding, leave pins CAZ1, and CAZ2 open (fOC = 2MHz). For ATM/SONET or other applications using scrambled NRZ data, select CAZ 0.1F, which typically provides fOC = 2kHz.
__________________Design Procedure
Program the LOS Assert Threshold
The loss-of-signal threshold is programmed by external resistor RTH. See the LOS Threshold vs. RTH graph in the Typical Operating Characteristics.
Select the Coupling Capacitors
The coupling capacitors (CIN, COUT) should be selected to minimize the receiver's deterministic jitter. Jitter is minimized when the input low-frequency cutoff (fIN) is placed at a low frequency. fIN = 1 / [2(50)(C)]
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3.0V to 5.5V, 1.25Gbps/2.5Gbps Limiting Amplifiers
Applications Information
Optical Hysteresis
In an optical receiver, the electrical power change at the limiting amplifier is 2x the optical power change. As an example, if a receiver's optical input power (x) increases by a factor of two, and the preamplifier is linear, then the voltage input to the limiting amplifier also increases by a factor of two. The optical power change is 10log(2x / x) = 10log(2) = +3dB. At the limiting amplifier, the electrical power change is:
10log
VCC_MODULE HOST VCC_HOST 4.7k
MAX3264/MAX3265/MAX3268/MAX3269
GBIC MODULE
MAX3264 MAX3265 MAX3268 LOS MAX3269
GENERALPURPOSE NPN
(2VIN )2 / RIN
VIN2 / RIN
= 10log(22 ) = 20log(2) = + 6dB
The MAX3264/MAX3265/MAX3268/MAX3269's typical voltage hysteresis is 4.4dB. This provides an optical hysteresis of 2.2dB.
Figure 8. Recommended GBIC LOS Circuit
GBIC Loss of Signal
In a GBIC application, the GBIC's LOS output must be high impedance when VCC_MODULE = GND. Figure 8 shows the recommended circuit to maintain high impedance. ESD protection diodes on the MAX3264/ MAX3265/MAX3268/MAX3269 LOS outputs can be turned on when VCC_HOST > VCC_MODULE.
OUT+ 470
PECL Terminations
The standard PECL termination (50 to VCC - 2V) is recommended for best performance and output characteristics (see Figure1). The data outputs operate at high speed and should always drive transmission lines with matched, balanced terminations. Figure 9 shows an alternate method for terminating the data outputs. The technique provides approximately 8mA DC bias current, with a 45 AC load, for the output termination. This technique is useful for viewing the output on an oscilloscope or changing the PECL reference voltage.
MAX3268 MAX3269
OUT470
50
50
DRIVING 50 TO GROUND
Figure 9. Alternative PECL Termination
Wire Bonding Dice
For high current density and reliable operation, the MAX3264/MAX3265/MAX3268/MAX3269 use gold metalization. Make connections to the dice with gold wire only, and use ballbonding techniques (wedge bonding is not recommended). Die-pad size is 4mils square, with a 6mil pitch. Die thickness is 15mils (0.375mm).
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3.0V to 5.5V, 1.25Gbps/2.5Gbps Limiting Amplifiers MAX3264/MAX3265/MAX3268/MAX3269
Typical Operating Circuits (continued)
VCC
VCC
MAX3268CUB MAX3269CUB
CIN 0.01F IN+ 100 INOUT50 TH RTH LOS VCC - 2V SIGNAL DETECT 50 OUT+
MAX3266 MAX3267
CIN 0.01F
Pin Configurations
TOP VIEW
CAZ1 1 CAZ2 2 GND 3 IN+ 4 IN- 5 GND 6 LEVEL 7 TH 8 16 N.C. 15 SQUELCH 14 VCC GND 1 IN+ INGND TH 2 3 4 5 10 VCC 9 OUT+ OUTVCC LOS
MAX3264 MAX3265
13 OUT+ 12 OUT11 VCC 10 LOS 9 LOS
MAX3265 MAX3268 MAX3269
8 7 6
MAX
TSSOP
NOTE: EXPOSED PADDLE IS GROUND.
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3.0V to 5.5V, 1.25Gbps/2.5Gbps Limiting Amplifiers
Selector Guide
PART MAX3264 MAX3265 MAX3268 MAX3269 *LEVEL pin grounded OUTPUT CML CML PECL PECL DATA RATE (Gbps) 1.25 2.5 1.25 2.5 PINPACKAGE 16 TSSOP-EP 16 TSSOP-EP 10 MAX-EP 10 MAX-EP 10 MAX-EP SQUELCH FUNCTION Selectable Selectable Disabled Disabled Disabled CML OUTPUT LEVEL Selectable Selectable Maximum* N/A N/A
MAX3264/MAX3265/MAX3268/MAX3269
Chip Topographies
MAX3264/MAX3265
CAZ1 N.C. CAZ1
MAX3268/MAX3269
N.C.
CAZ2 GND IN+ INGND LEVEL
SQUELCH VCC OUT+ OUTVCC LOS 0.061" (1.55mm)
CAZ2 GND IN+ INGND
SQUELCH VCC OUT+ OUTVCC LOS 0.061" (1.55mm)
TH
N.C. 0.061" (1.55mm)
LOS
TH
N.C. 0.061" (1.55mm)
LOS
MAX3264/MAX3265 TRANSISTOR COUNT: 726 MAX3268/MAX3269 TRANSISTOR COUNT: 728 SUBSTRATE CONNECTED TO GND
______________________________________________________________________________________
15
3.0V to 5.5V, 1.25Gbps/2.5Gbps Limiting Amplifiers MAX3264/MAX3265/MAX3268/MAX3269
Package Information
10LUMAX.EPS
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.
16 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
TSSOP.EPS

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