19-1523; Rev 7, 2/06
+3.0V to +5.5V, 1.25Gbps/2.5Gbps
Limiting Amplifiers
Features
♦ +3.0V to +5.5V Supply Voltage
♦ Low Deterministic Jitter
14ps (MAX3264)
11ps (MAX3265/MAX3765)
♦ 150ps (max) Edge Speed (MAX3265/MAX3765)
300ps (max) Edge Speed (MAX3264)
♦ Programmable Signal-Detect Function
♦ Choice of CML or PECL Output Interface
♦ 10-Pin µMAX or 16-Pin TSSOP Package
Ordering Information
PART
TEMP RANGE
Applications
PIN-PACKAGE
0°C to +70°C
16 TSSOP-EP*
MAX3264CUE+
0°C to +70°C
16 TSSOP-EP*
MAX3264C/D
0°C to +70°C
Dice**
MAX3265CUE
0°C to +70°C
16 TSSOP-EP*
MAX3265CUE+
0°C to +70°C
16 TSSOP-EP*
MAX3265CUB
0°C to +70°C
10 µMAX-EP*
MAX3264CUE
Gigabit Ethernet Optical Receivers
MAX3265CUB+
0°C to +70°C
10 µMAX-EP*
Fibre Channel Optical Receivers
MAX3265EUE
-40°C to +85°C
16 TSSOP-EP*
System Interconnect
MAX3265EUE+
-40°C to +85°C
16 TSSOP-EP*
MAX3265C/D
ATM Optical Receivers
0°C to +70°C
Dice**
+Denotes lead-free package.
*EP = Exposed paddle.
**Dice are designed to operate from 0°C to +70°C, but are tested
and guaranteed only at TA = +25°C.
Selector Guide appears at end of data sheet.
Pin Configurations appear at end of data sheet.
Ordering Information continued at end of data sheet.
Typical Operating Circuits
CAZ
VCC
CAZ1
VCC
VCC
CAZ2
MAX3264CUE
MAX3265CUE
MAX3265EUE
CIN
0.01µF
RTERM
0.01µF
OUT+
IN+
100Ω
IN-
MAX3266
MAX3267
0.01µF
OUT-
CIN
0.01µF
RL
100Ω
RTERM
TH
SQUELCH
LOS
LEVEL
LOSS N.C.
OF
SIGNAL
N.C.
LOS
VCC
RTH
Typical Operating Circuits continued at end of data sheet.
N.C.
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX3264/MAX3265/MAX3268/MAX3269/MAX3765/MAX3768
General Description
The 1.25Gbps MAX3264/MAX3268/MAX3768 and the
2.5Gbps MAX3265/MAX3269/MAX3765 limiting amplifiers are designed for Gigabit Ethernet and Fibre
Channel optical receiver systems. The amplifiers accept
a wide range of input voltages and provide constantlevel 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/MAX3765 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/MAX3768 feature standards-compliant positive-referenced emitter-coupled logic (PECL) data outputs and are available in a tiny 10-pin µMAX package
that is ideal for small-form-factor (SFF) receivers.
MAX3264/MAX3265/MAX3268/MAX3269/MAX3765/MAX3768
+3.0V to +5.5V, 1.25Gbps/2.5Gbps
Limiting Amplifiers
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 = +70°C)
16-Pin TSSOP (derate 27mW/°C above +70°C) .........2162mW
10-Pin µMAX (derate 20mW/°C above +70°C) ...........1600mW
Operating Ambient Temperature Range .............-40°C to +85°C
Storage Temperature Range .............................-55°C to +150°C
Processing Temperature (dice) .......................................+400°C
Lead Temperature (soldering, 10s) .................................+300°C
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 = 0°C to +70°C. Typical values are at VCC = +3.3V, TA = +25°C,
unless otherwise noted.) (Note 1)
PARAMETER
Data Rate
Input Voltage Range
Deterministic Jitter
Random Jitter
CONDITIONS
MAX3264/MAX3268/MAX3768
1.25
2.5
MAX
5
1200
MAX3265/MAX3269/MAX3765
10
1200
MAX3264/MAX3268/MAX3768 (Notes 2, 3)
14
30
MAX3265/MAX3269/MAX3765 (Notes 2, 3)
11
25
MAX3264/MAX3268/MAX3768 (Notes 2, 4)
15
MAX3265/MAX3269/MAX3765 (Notes 2, 4)
8
80
MAX3265/MAX3765 (Note 6)
MAX3268/MAX3768 (Note 5)
80
LOS Hysteresis
(Notes 2, 7)
LOS Assert/Deassert Time
(Notes 7, 8)
Low LOS Assert Level
RTH = 2.5kΩ
Low LOS Deassert Level
RTH = 2.5kΩ
2.5
UNITS
Gbps
MAX3264/MAX3268/MAX3768
MAX3269 (Note 6)
2
TYP
MAX3265/MAX3269/MAX3765
MAX3264 (Note 5)
Data Output Edge Speed
MIN
mV
psp-p
psRMS
175
300
100
150
150
300
100
150
ps
4.4
dB
1
µs
MAX3264/MAX3268/MAX3768
1.20
2.6
MAX3265/MAX3269/MAX3765
2.20
4.8
MAX3264/MAX3268/MAX3768
4.5
MAX3265/MAX3269/MAX3765
8.5
_______________________________________________________________________________________
mV
mV
+3.0V to +5.5V, 1.25Gbps/2.5Gbps
Limiting Amplifiers
(Data outputs terminated per Figure 1, VCC = +3.0V to +5.5V, TA = 0°C to +70°C. Typical values are at VCC = +3.3V, TA = +25°C,
unless otherwise noted.) (Note 1)
PARAMETER
CONDITIONS
Medium LOS Assert Level
RTH = 7kΩ
Medium LOS Deassert Level
RTH = 7kΩ
High LOS Assert Level
RTH = 20kΩ
High LOS Deassert Level
RTH = 20kΩ
MIN
TYP
MAX3264/MAX3268/MAX3768
5.6
9
MAX3265/MAX3269/MAX3765
9.9
16
15
19.8
MAX3265/MAX3269/MAX3765
40.5
MAX3264/MAX3268/MAX3768
9.4
27
21.6
MAX3265/MAX3269/MAX3765
18.0
41.5
MAX3264/MAX3268/MAX3768
35
MAX3265/MAX3269/MAX3765
67
Input-Referred Noise
CML Output Voltage
IN+ to IN-
UNITS
mV
MAX3264/MAX3268/MAX3768
Squelch Input Current
Differential Input Resistance
MAX
mV
mV
mV
0
80
400
µA
97
100
103
Ω
MAX3264/MAX3268/MAX3768
150
MAX3265/MAX3269/MAX3765
230
LEVEL = open, RLOAD = 50Ω
550
LEVEL = GND, RLOAD = 75Ω
1100
µVRMS
1200
1270
1800
mV
PECL Output High Voltage
Referenced to VCC
-1.025
-0.880
V
PECL Output Low Voltage
Referenced to VCC
-1.810
-1.620
V
LOS Output High Voltage
ILOS = -30µA
LOS Output Low Voltage
ILOS = +1.2mA
0.4
V
Output Signal When Squelched
Outputs AC-coupled
20
Power-Supply Rejection Ratio
Low-Frequency Cutoff
Output Resistance (Single Ended)
Power-Supply Current
2.4
V
mV
f < 2MHz
20
dB
CAZ = open
2
MHz
CAZ = 0.1µF
2
kHz
MAX3264/MAX3265/MAX3765
85
MAX3268/MAX3269/MAX3768
Figure 2
Output not
squelched
Output squelched
100
115
4
MAX3268
39
62
MAX3269
48
78
MAX3264
38
62
MAX3265
50
76
MAX3765
50
76
MAX3768
39
62
MAX3765
64
90
Ω
mA
_______________________________________________________________________________________
3
MAX3264/MAX3265/MAX3268/MAX3269/MAX3765/MAX3768
ELECTRICAL CHARACTERISTICS (continued)
MAX3264/MAX3265/MAX3268/MAX3269/MAX3765/MAX3768
+3.0V to +5.5V, 1.25Gbps/2.5Gbps
Limiting Amplifiers
ELECTRICAL CHARACTERISTICS—MAX3265EUE
(Data outputs terminated per Figure 1, VCC = +3.0V to +5.5V, TA = -40°C to +85°C. Typical values are at VCC = +3.3V, TA = +25°C,
unless otherwise noted.) (Note 1)
PARAMETER
CONDITIONS
MIN
Data Rate
TYP
Input Voltage Range
10
(Notes 2, 3)
11
Random Jitter
(Notes 2, 4)
8
Data Output Edge Speed
(Note 6)
LOS Hysteresis
(Notes 2, 7)
LOS Assert/Deassert Time
(Notes 7, 8)
Low LOS Assert Level
RTH = 2.5kΩ
Low LOS Deassert Level
RTH = 2.5kΩ
Medium LOS Assert Level
RTH = 7kΩ
Medium LOS Deassert Level
RTH = 7kΩ
High LOS Assert Level
RTH = 20kΩ
High LOS Deassert Level
RTH = 20kΩ
100
2.2
2.20
155
ps
1
µs
mV
4.8
13.6
mV
mV
16
43.0
mV
mV
41.5
67
111
mV
0
80
400
µA
IN+ to IN-
97
100
103
Ω
LEVEL = open, RLOAD = 50Ω
550
LEVEL = GND, RLOAD = 75Ω
1100
Squelch Input Current
Input-Referred Noise
CML Output Voltage
psp-p
psRMS
dB
27
18.0
25
mV
4.4
8.5
9.9
UNITS
Gbps
1200
Deterministic Jitter
Differential Input Resistance
MAX
2.5
230
µVRMS
1200
1270
1800
mV
LOS Output High Voltage
ILOS = -30µA
LOS Output Low Voltage
ILOS = +1.2mA
Output Signal When Squelched
Outputs AC-coupled
20
mV
Power-Supply Rejection Ratio
f < 2MHz
20
dB
CAZ = open
2
MHz
CAZ = 0.1µF
2
Low-Frequency Cutoff
Output Resistance (single ended)
Power-Supply Current
2.4
85
Figure 2
V
0.450
V
kHz
100
115
Ω
50
76
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 four-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 four-pole, lowpass, Bessel filter (frequency bandwidth at 75% of the maximum data rate). For Fibre Channel and Gigabit Ethernet applications, the peak-topeak 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
1100
MAX3265/MAX3269/MAX3765
700
5.0
RTH = 7kΩ
4.5
6.0
RTH = 25kΩ
4.0
500
2
4
6
8
10
RTH = 4.6kΩ
5.0
4.5
RTH = 16kΩ
3.5
0
12
10
20
30
40
50
60
-40
70
-15
10
35
60
INPUT VOLTAGE (mV)
TEMPERATURE (°C)
TEMPERATURE (°C)
MAX3264/MAX3268/MAX3768
DETERMINISTIC JITTER
vs. INPUT AMPLITUDE
MAX3264/MAX3268/MAX3768
RANDOM JITTER
vs. INPUT AMPLITUDE
MAX3265/MAX3269/MAX3765
DETERMINISTIC JITTER
vs. INPUT AMPLITUDE
14
12
RMS JITTER (ps)
25
20
15
10
85
30
MAX3264/5/8/9 TOC06
16
MAX3264/5/8/9 TOC04
30
25
20
10
JITTER (ps)
0
5.5
4.0
3.5
300
JITTER (ps)
5.5
MAX3264/5/8/9 TOC03
6.0
LOS HYSTERESIS (dB)
1300
MAX3264/5/8/9 TOC03a
MAX3264/MAX3268
6.5
MAX3264/5/8/9 TOC05
OUTPUT VOLTAGE (mV)
1500
6.5
LOS HYSTERESIS (dB)
MAX3264/5/8/9 TOC01a
1700
900
MAX3265EUE
LOS HYSTERESIS vs. TEMPERATURE
MAX3264
LOS HYSTERESIS vs. TEMPERATURE
OUTPUT VOLTAGE
vs. INPUT VOLTAGE
8
6
15
10
4
0
0
0
200
400
600
800
1000
0
1200
INPUT AMPLITUDE (mV)
MAX3265/MAX3269/MAX3765
RANDOM JITTER
vs. INPUT AMPLITUDE
MAX3264/5/8/9 TOC07
8
7
6
5
10
20
30
40
0
50
200
400
600
800
1000
INPUT AMPLITUDE (mV)
INPUT AMPLITUDE (mV)
LOSS OF SIGNAL WITH SQUELCH
MAX3268/MAX3768
DATA OUTPUT EYE DIAGRAM
(MINIMUM INPUT)
1200
MAX3264/5/8/9 TOC08
0
RMS JITTER (ps)
5
2
MAX3264/5/8/9 TOC09
5
VIN
VOUT
300mV/div
4
3
VLOS
2
1
0
0
10
20
30
40
50
500ns/div
200ps/div
INPUT AMPLITUDE (mV)
_______________________________________________________________________________________
5
MAX3264/MAX3265/MAX3268/MAX3269/MAX3765/MAX3768
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
MAX3264
DATA OUTPUT EYE DIAGRAM AT
1.25Gbps (MINIMUM INPUT)
MAX3265/MAX3765
DATA OUTPUT EYE DIAGRAM
2.5Gbps (MINIMUM INPUT)
50mV/div
OUTPUT VSWR vs. FREQUENCY
4.0
25
20
3.5
VSWR
15
2.0
5
1.5
0
100ps/div
1.0
100k
MAX3264
LOSS-OF-SIGNAL THRESHOLD vs. RTH
25
20
15
10
100M
1G
0.5
1.0
1.5
2.5
2.0
FREQUENCY (GHz)
MAX3265/MAX3765
LOSS-OF-SIGNAL THRESHOLD vs. RTH
COMMON-MODE REJECTION RATIO
vs. FREQUENCY
50
55
30
20
MAX3268/MAX3768
50
45
40
40
3.0
35
30
25
MAX3265/MAX3765
20
15
10
5
0
FREQUENCY (Hz)
CMRR (dB)
30
10M
MAX3264/5/8/9 TOC19
35
1M
60
LOS ASSERT THRESHOLD (mV)
MAX3264/5/8/9 TOC18
40
2.5
MAX3264/5/8/9 TOC20
PSRR (dB)
3.0
10
10
0
5
0
0
6
MAX3264/5/8/9 TOC15
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX3264/5/8/9 TOC14
200ps/div
MAX3264/5/8/9 TOC13
150mV/div
100ps/div
200ps/div
MAX3265/MAX3765
DATA OUTPUT EYE DIAGRAM
2.5Gbps (MAXIMUM INPUT)
150mV/div
MAX3264/5/8/9 TOC12
MAX3264/5/8/9 TOC11
MAX3264/5/8/9 TOC10
MAX3264
DATA OUTPUT EYE DIAGRAM AT
1.25Gbps (MAXIMUM INPUT)
150mV/div
LOS ASSERT THRESHOLD (mV)
MAX3264/MAX3265/MAX3268/MAX3269/MAX3765/MAX3768
+3.0V to +5.5V, 1.25Gbps/2.5Gbps
Limiting Amplifiers
5
10
15
20
RTH (kΩ)
25
30
35
0
5
10
15
RTH (kΩ)
20
25
30
1M
10M
100M
FREQUENCY (Hz)
_______________________________________________________________________________________
1G
10G
+3.0V to +5.5V, 1.25Gbps/2.5Gbps
Limiting Amplifiers
PIN
NAME
FUNCTION
µMAX
TSSOP
1, 4
3, 6
GND
Supply Ground
2
4
IN+
Noninverted Input Signal
3
5
IN-
Inverted Input Signal
5
8
TH
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) is asserted. Refer to
Typical Operating Characteristics and Design Procedure.
6
9
LOS
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.
7, 10
11, 14
VCC
Supply Voltage
8
12
OUT-
Inverted Data Output
9
13
OUT+
Noninverted Data Output
—
1
CAZ1
Offset-Correction-Loop Capacitor. A capacitor connected between this pin and
CAZ2 extends the time constant of the offset correction loop.
—
2
CAZ2
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.
—
7
LEVEL
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/MAX3765CUB, LEVEL is
internally connected to ground.)
—
10
LOS
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
MAX3265/MAX3268/MAX3269 10-pin µMAX, SQUELCH is not connected. In the
MAX3765/MAX3768, SQUELCH is internally connected to VCC.)
—
15
SQUELCH
—
16
N.C.
EP
EP
Exposed
Paddle
No Connection
Ground. The exposed paddle must be soldered to the circuit–board ground for
proper thermal performance.
_______________________________________________________________________________________
7
MAX3264/MAX3265/MAX3268/MAX3269/MAX3765/MAX3768
Pin Description
MAX3264/MAX3265/MAX3268/MAX3269/MAX3765/MAX3768
+3.0V to +5.5V, 1.25Gbps/2.5Gbps
Limiting Amplifiers
VCC
VCC
VCC
VCC
100Ω
100Ω
100Ω
RTERM
100Ω
300Ω
100Ω
COUT
100Ω
RTERM
300Ω
COUT
2 x RLOAD
150Ω
2 x RLOAD
100Ω
COUT
COUT
MAX3264
MAX3265
MAX3765
MAX3264
MAX3265
MAX3765
(a) MAX3264/MAX3265/MAX3765 WITH 50Ω TERMINATION
(b) MAX3264/MAX3265/MAX3765 WITH 75Ω TERMINATION
VCC
MAX3268
MAX3269
MAX3768
OUTOUT+
RTERM
50Ω
50Ω
(c) MAX3268/MAX3269/MAX3768 OUTPUT TERMINATION
VCC - 2V
Figure 1. Data Output Termination
8
_______________________________________________________________________________________
+3.0V to +5.5V, 1.25Gbps/2.5Gbps
Limiting Amplifiers
MAX3264/MAX3265/MAX3268/MAX3269/MAX3765/MAX3768
VCC
ICC
IOUT
100Ω
100Ω
MAX3264CUE: OPEN
MAX3265CUE: OPEN
SQUELCH MAX3265CUB: GND (INTERNAL)
MAX3765CUB: VCC (INTERNAL)
CONTROL
MAX3264
MAX3265
MAX3765
LEVEL
MAX3264CUE: OPEN
MAX3265CUE: OPEN
MAX3265CUB: GND (INTERNAL)
MAX3765CUB: GND (INTERNAL)
RTH
2.5kΩ
(a) CML SUPPLY CURRENT (ICC)
VCC
ICC
OUT+
MAX3268
MAX3269
MAX3768
OPEN
OUTOPEN
RTH
2.5kΩ
(b) PECL SUPPLY CURRENT (ICC)
Figure 2. Power-Supply Current Measurement
_______________________________________________________________________________________
9
MAX3264/MAX3265/MAX3268/MAX3269/MAX3765/MAX3768
+3.0V to +5.5V, 1.25Gbps/2.5Gbps
Limiting Amplifiers
RMS Power Detect with
Loss-of-Signal Indicator
_______________Detailed Description
Figure 3 is a functional diagram of the MAX3264/
MAX3265/MAX3268/MAX3269/MAX3765/MAX3768 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/MAX3765 produce a CML output, while the MAX3268/MAX3269/
MAX3768 produce a PECL-compatible output signal.
Schematics of these input/output circuits are shown in
Figures 4 through 7.
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 8kΩ (MAX3265/MAX3269/MAX3765) or
16kΩ (MAX3264/MAX3268/MAX3768) pullup resistors.
The LOS outputs meet TTL voltage specifications when
loaded with a resistor ≥ 4.7kΩ.
TH
VCC
RLOS = 8kΩ (MAX3265/MAX3269/MAX3765)
RLOS = 16kΩ (MAX3264/MAX3268/MAX3768)
MAX3264
MAX3265
MAX3268
MAX3269
MAX3765
MAX3768
RLOS
LOS
TTL
VCC
POWER DETECT
WITH
COMPARATOR
RLOS
LOS
TTL
GAIN
IN+
OUT+
100Ω
INPUT
BUFFER
OUTPUT
BUFFER
IN-
OUT-
SQUELCH
LOWPASS
OFFSET
CORRECTION
CONTROL
LEVEL
100pF
CAZ1
CAZ2
TOTAL GAIN = 55dB (MAX3264/MAX3268/MAX3768)
TOTAL GAIN = 49dB (MAX3265/MAX3269/MAX3765)
Figure 3. Functional Diagram
10
______________________________________________________________________________________
+3.0V to +5.5V, 1.25Gbps/2.5Gbps
Limiting Amplifiers
CML Output Buffer
The MAX3264/MAX3265/MAX3765 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.
Gain Stage and Offset Correction
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 µMAX package of
the MAX3265/MAX3268/MAX3269, the SQUELCH function is left internally unconnected. In the MAX3765/
MAX3768, the SQUELCH function is always enabled by
internally connecting it to VCC. SQUELCH operation for
the MAX3264/MAX3265 is described in Table 1.
The limiting amplifier provides approximately 55dB
(MAX3264/MAX3268/MAX3768) or 49dB (MAX3265/
MAX3269/MAX3765) of gain. This large gain makes the
amplifier susceptible to small DC offsets in the input signal. DC offsets as low as 1mV 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 100µV.
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.
LEVEL PIN
VOLTAGE WHEN SQUELCHED
OUT-
OUT+
Open
VCC - 100mV
VCC
GND
VCC - 100mV
VCC - 100mV
Internal Input/Output Schematics
VCC
500Ω
500Ω
VCC
0.25pF
IN+
110Ω
IN-
RT
0.25pF
LOS
ESD
STRUCTURES
ESD
STRUCTURE
GND
RT = 8kΩ (MAX3265/MAX3269/MAX3765)
RT = 16kΩ (MAX3264/MAX3268/MAX3768)
GND
Figure 4. Input Circuit
Figure 5. LOS Output Circuit
______________________________________________________________________________________
11
MAX3264/MAX3265/MAX3268/MAX3269/MAX3765/MAX3768
Input Buffer
The input buffer is designed to accept input signals
from the MAX3266/MAX3267 transimpedance amplifiers. The input buffer provides a 100Ω 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.
MAX3264/MAX3265/MAX3268/MAX3269/MAX3765/MAX3768
+3.0V to +5.5V, 1.25Gbps/2.5Gbps
Limiting Amplifiers
VCC
VCC
ESD
STRUCTURES
ESD
STRUCTURES
100Ω
100Ω
OUT+
OUT-
OUT+
OUT-
GND
GND
LEVEL
Figure 6. PECL Output Circuit
Figure 7. CML Output Circuit
The buffer’s output impedance is determined by the parallel combination of internal and external pullup 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.
minimized when the input low-frequency cutoff (fIN) is
placed at a low frequency:
fIN = 1 / [2π(50)(C)]
For Fibre Channel, Gigabit Ethernet, or other applications using 8B/10B data coding, select (CIN, COUT) ≥
0.01µF, which provides fIN < 320kHz. For ATM/SONET
or other applications using scrambled NRZ data, select
(CIN, COUT) ≥ 0.1µF, which provides fIN < 32kHz.
PECL Output Buffer
The MAX3268/MAX3269/MAX3768 offer an industrystandard 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 µMAX,
SQUELCH is left unconnected.
__________________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
12
Select the Offset-Correction Capacitor
(MAX3264/MAX3265 TSSOP 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 / [2π 60k (CAZ + 100pF)]
= 200 x 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 ≥
0.1µF, which typically provides fOC = 2kHz.
______________________________________________________________________________________
+3.0V to +5.5V, 1.25Gbps/2.5Gbps
Limiting Amplifiers
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
(2VIN )2 / RIN
VIN2 / RIN
= 10log(22 ) = 20log(2) = + 6dB
The MAX3264/MAX3265/MAX3268/MAX3269/MAX3765s’
typical voltage hysteresis is 4.4dB. This provides an optical hysteresis of 2.2dB.
VCC_MODULE
MAX3264/MAX3265/MAX3268/MAX3269/MAX3765/MAX3768
Applications Information
HOST
VCC_HOST
GBIC MODULE
4.7kΩ
MAX3264
MAX3265
MAX3268 LOS
MAX3269
MAX3765
MAX3768
GENERALPURPOSE
NPN
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/MAX3765/MAX3768
LOS outputs can be turned on when V CC_ HOST >
VCC_MODULE.
PECL Terminations
The standard PECL termination (50Ω to VCC - 2V) is
recommended for best performance and output characteristics (see Figure 1). 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 45Ω AC load, for the output termination. This technique is useful for viewing the
output on an oscilloscope or changing the PECL reference voltage.
OUT+
470Ω
50Ω
470Ω
50Ω
MAX3268
MAX3269
MAX3768
OUT-
DRIVING 50Ω 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 4-mils square,
with a 6-mil pitch. Die thickness is 15 mils (0.375mm).
______________________________________________________________________________________
13
MAX3264/MAX3265/MAX3268/MAX3269/MAX3765/MAX3768
+3.0V to +5.5V, 1.25Gbps/2.5Gbps
Limiting Amplifiers
Typical Operating Circuits (continued)
VCC
VCC
MAX3268CUB
MAX3269CUB
MAX3768CUB
CIN
0.01µF
OUT+
IN+
100Ω
IN-
MAX3266
MAX3267
OUT-
CIN
0.01µF
50Ω
50Ω
LOS
TH
RTH
VCC - 2V
SIGNAL DETECT
Ordering Information (continued)
PART
TEMP RANGE
Pin Configurations
PIN-PACKAGE
MAX3268CUB
0°C to +70°C
10 µMAX-EP*
MAX3268CUB+
0°C to +70°C
10 µMAX-EP*
MAX3268C/D
0°C to +70°C
Dice**
MAX3269CUB
0°C to +70°C
10 µMAX-EP*
MAX3269CUB+
0°C to +70°C
10 µMAX-EP*
MAX3269C/D
0°C to +70°C
Dice**
MAX3765CUB
0°C to +70°C
10 µMAX-EP*
MAX3765CUB+
0°C to +70°C
10 µMAX-EP*
MAX3768CUB
0°C to +70°C
10 µMAX-EP*
MAX3768CUB+
0°C to +70°C
10 µMAX-EP*
+Denotes lead-free package.
*EP = Exposed paddle.
**Dice are designed to operate from 0°C to +70°C, but are tested
and guaranteed only at TA = +25°C.
TOP VIEW
CAZ1 1
16 N.C.
CAZ2 2
15 SQUELCH
GND 3
14 VCC
IN+ 4
IN- 5
MAX3264
MAX3265
13 OUT+
12 OUT-
GND 6
11 VCC
LEVEL 7
10 LOS
9
TH 8
TSSOP
NOTE: EXPOSED PADDLE IS GROUND.
GND 1
IN+
10 VCC
2
IN-
3
GND
4
TH
5
MAX3265
MAX3268
MAX3269
MAX3765
MAX3768
9
OUT+
8
OUT-
7
VCC
6
LOS
µMAX
14
LOS
______________________________________________________________________________________
+3.0V to +5.5V, 1.25Gbps/2.5Gbps
Limiting Amplifiers
PART
OUTPUT
DATA RATE
(Gbps)
PINPACKAGE
SQUELCH
FUNCTION
CML OUTPUT
LEVEL
MAX3264
CML
1.25
MAX3265
CML
2.5
MAX3268
PECL
1.25
16 TSSOP-EP
16 TSSOP-EP
10 µMAX-EP
10 µMAX-EP
Selectable
Selectable
Disabled
Disabled
Selectable
Selectable
Maximum*
N/A
MAX3269
PECL
2.5
10 µMAX-EP
Disabled
N/A
MAX3765
MAX3768
CML
PECL
2.5
1.25
10 µMAX-EP
10 µMAX-EP
Enabled
Enabled
Maximum*
N/A
*LEVEL pin grounded
Chip Topographies
MAX3264/MAX3265/MAX3765
MAX3268/MAX3269/MAX3768
N.C.
CAZ1
CAZ2
SQUELCH
GND
VCC
IN+
OUT+
IN-
OUT-
GND
VCC
LEVEL
LOS
TH
N.C.
LOS
0.061"
(1.55mm)
N.C.
CAZ1
0.061"
(1.55mm)
CAZ2
SQUELCH
GND
VCC
IN+
OUT+
IN-
OUT-
0.061"
(1.55mm)
VCC
GND
LOS
TH
N.C.
LOS
0.061"
(1.55mm)
MAX3264/MAX3265/MAX3765
TRANSISTOR COUNT: 726
MAX3268/MAX3269/MAX3768
TRANSISTOR COUNT: 728
SUBSTRATE CONNECTED TO GND
______________________________________________________________________________________
15
MAX3264/MAX3265/MAX3268/MAX3269/MAX3765/MAX3768
Selector Guide
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
e
10LUMAX.EPS
MAX3264/MAX3265/MAX3268/MAX3269/MAX3765/MAX3768
+3.0V to +5.5V, 1.25Gbps/2.5Gbps
Limiting Amplifiers
4X S
10
INCHES
10
H
Ø0.50±0.1
0.6±0.1
1
1
0.6±0.1
BOTTOM VIEW
TOP VIEW
D2
MILLIMETERS
MAX
DIM MIN
0.043
A
0.006
A1
0.002
A2
0.030
0.037
0.120
D1
0.116
0.118
D2
0.114
0.120
E1
0.116
0.118
E2
0.114
0.199
H
0.187
L
0.0157 0.0275
L1
0.037 REF
0.0106
b
0.007
e
0.0197 BSC
c
0.0035 0.0078
0.0196 REF
S
α
0°
6°
MAX
MIN
1.10
0.15
0.05
0.75
0.95
3.05
2.95
2.89
3.00
3.05
2.95
2.89
3.00
4.75
5.05
0.40
0.70
0.940 REF
0.177
0.270
0.500 BSC
0.090
0.200
0.498 REF
0°
6°
E2
GAGE PLANE
A2
c
A
b
D1
FRONT VIEW
A1
α
E1
L
L1
SIDE VIEW
PROPRIETARY INFORMATION
TITLE:
PACKAGE OUTLINE, 10L uMAX/uSOP
APPROVAL
DOCUMENT CONTROL NO.
21-0061
16
______________________________________________________________________________________
REV.
1
1
+3.0V to +5.5V, 1.25Gbps/2.5Gbps
Limiting Amplifiers
TSSOP 4.4mm BODY.EPS
XX XX
PACKAGE OUTLINE, TSSOP, 4.40 MM BODY,
EXPOSED PAD
21-0108
E
1
1
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.
17 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2006 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products, Inc.
MAX3264/MAX3265/MAX3268/MAX3269/MAX3765/MAX3768
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
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