19-3386; Rev 2; 6/07
Low-Power, 622Mbps to 3.2Gbps
Limiting Amplifier
General Description
The MAX3746 multirate limiting amplifier functions as a
data quantizer for SONET, Fibre-Channel, and Gigabit
Ethernet optical receivers. The amplifier accepts a wide
range of input voltages and provides selectable-level,
current-mode logic (CML) output voltages with con-
trolled edge speeds. A received-signal-strength indica-
tor (RSSI) is available when the MAX3746 is
DC-coupled to the MAX3744/MAX3724 SFP transim-
pedance amplifier (TIA). A receiver consisting of the
MAX3744/MAX3724 and the MAX3746 can provide up
to 19dB RSSI dynamic range. Additional features
include a programmable loss-of-signal (LOS) detect, an
optional disable function (DISABLE), and an
output-signal polarity reversal (OUTPOL). Output dis-
able can be used to implement squelch.
The combination of the MAX3746 and the MAX3744/
MAX3724 allows for the implementation of all the small-
form-factor SFF-8472 digital diagnostic specifications
using a standard 4-pin TO-46 header.
The MAX3746 is pin-for-pin compatible with the
MAX3748A limiting amplifier and consumes 30% less
power. The MAX3746 is packaged in a 3mm x 3mm,
16-pin QFN package.
♦
SFP Reference Design Available
♦
Low 115mW Power Consumption
♦
16-Pin QFN Package with 3mm x 3mm Footprint
♦
70ps Rise and Fall Time
♦
Loss-of-Signal with Programmable Threshold
♦
RSSI Interface (with MAX3744/MAX3724 TIA)
♦
Output Disable
♦
Polarity Select
♦
8.4ps
P-P
Deterministic Jitter (3.2Gbps)
♦
Improved EMI Performance
♦
Selectable CML Output levels
♦
Pin Compatible with MAX3748A
Features
MAX3746
Ordering Information
PART
MAX3746ETE
MAX3746HETE*
TEMP RANGE
PIN-
PACKAGE
PKG CODE
T1633F-3
T1633F-3
-40°C to +85°C 16 Thin QFN
-40°C to +85°C 16 Thin QFN
Applications
Gigabit Ethernet SFF/SFP Transceiver Modules
Fibre-Channel SFF/SFP Transceiver Modules
Multirate OC-12 to OC48-FEC SFF/SFP
Transceiver Modules
*The
MAX3746HETE is a hybrid lead-free package. See the
Detailed Description
section for more information.
Pin Configuration appears at end of data sheet.
Typical Operating Circuits continued at end of data sheet.
Typical Operating Circuits
SFP OPTICAL RECEIVER
SUPPLY FILTER
4-PIN TO HEADER
OUTPOL
V
CC
HOST BOARD
HOST FILTER
V
CC
_RX
0.1μF
IN+
MAX3744 TIA
OUT+
0.1μF
50Ω
SERDES
50Ω
IN-
OUT-
MAX3746
RSSI
TH
R
TH
= 14kΩ
GND
DISABLE
LOS
4.7kΩ TO 10kΩ
2.97V TO 3.6V
LOS
R1
3kΩ
C1
0.1μF
DS1859
3-INPUT DIAGNOSTIC
MONITOR
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Low-Power, 622Mbps to 3.2Gbps
Limiting Amplifier
MAX3746
ABSOLUTE MAXIMUM RATINGS
Power-Supply Voltage (V
CC
) .................................-0.5V to +4.5V
Voltage at IN+, IN- ..........................(V
CC
- 2.4V) to (V
CC
+ 0.5V)
Voltage at DISABLE, OUTPOL, RSSI,
LOS, TH ...................................................-0.5V to (V
CC
+ 0.5V)
Current into LOS.....................................................1mA to +9mA
Differential Input Voltage (IN+ - IN-) .....................................2.5V
Continuous Current at CML Outputs
(OUT+, OUT-) ................................................-25mA to +25mA
Continuous Power Dissipation (T
A
= + 70°C)
16-Pin QFN (derate 17.7mW above +70°C) .....................1.4W
Operating Junction Temperature Range (T
J
) ....-55°C to +150°C
Storage Ambient Temperature Range (Ts) .......-55°C to +150°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
(V
CC
= +2.97V to +3.63V, CML output load is 50Ω to V
CC
, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at V
CC
=
+3.3V, T
A
= +25°C, unless otherwise specified. The data input transition time is controlled by 4th-order Bessel filter with f
-3dB
= 0.75 x
2.667GHz for all data rates of 2.667Gbps and below, and with f
-3dB
= 0.75 x 3.2GHz for a data rate of 3.2Gbps.)
PARAMETER
Single-Ended Input Resistance
Input Return Loss
Input Sensitivity
Input Overload
Single-Ended Output Resistance
Output Return Loss
SYMBOL
R
IN
se S
11
diff S
11
V
IN-MIN
V
IN-MAX
R
OUT
diff S
22
CONDITIONS
Single ended to V
CC
Single ended, f < 3GHz, DUT is powered on
Differential, f < 3GHz, DUT is powered on
(Note 1)
(Note 1)
Single ended to V
CC
Differential, f < 3GHz, DUT is powered on
4mV
P-P
<
V
IN
<
1200mV
P-P
,
OUTPOL connected to V
CC
or GND
4mV
P-P
<
V
IN
<
1200mV
P-P
,
OUTPOL open or connected to 30kΩ
Outputs AC-coupled,
V
IN-MAX
applied to input (Note 2)
K28.5 pattern at 3.2Gbps (Note 2)
K28.5 pattern at 3.2Gbps at T
A
= +100°C
2
23
- 1 PRBS equivalent at 2.7Gbps (Note 2)
2
23
- 1 PRBS equivalent pattern at 2.7Gbps
at T
A
= +100°C
Deterministic Jitter
(Note 3)
DJ
K28.5 pattern at 2.1Gbps
K28.5 pattern at 2.1Gbps at T
A
= +100°C
2
23
- 1 PRBS equivalent pattern at 622Mbps
(Note 2)
2
23
- 1 PRBS equivalent pattern at 622Mbps
at T
A
= +100°C
8.4
10.2
11.6
13.1
8
9.7
42.5
47.8
69
20
ps
P-P
23
600
400
1200
42
50
20
800
500
1000
mV
P-P
600
10
18
mV
P-P
58
MIN
42
TYP
50
14
15
2
4
MAX
58
UNITS
Ω
dB
mV
P-P
mV
P-P
Ω
dB
CML Differential Output Voltage
Differential Output Signal when
Disabled
2
_______________________________________________________________________________________
Low-Power, 622Mbps to 3.2Gbps
Limiting Amplifier
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +2.97V to +3.63V, CML output load is 50Ω to V
CC
, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at V
CC
=
3.3V, T
A
= +25°C, unless otherwise specified. The data input transition time is controlled by 4th-order Bessel filter with f
-3dB
= 0.75 x
2.667GHz for all data rates of 2.667Gbps and below, and with f
-3dB
= 0.75 x 3.2GHz for a data rate of 3.2Gbps.)
PARAMETER
Random Jitter
Data Output Transition
Time
Input-ReferredNoise
Low-Frequency Cutoff
Includes the CML output current; OUTPOL
connected to V
CC
or GND
Power-Supply Current
I
CC
Includes the CML output current; OUTPOL
open or connected to 30kΩ to GND
Excludes the CML output current and the
CM_RSSI circuitry; OUTPOL connected to
V
CC
or GND (Note 5)
Power-Supply Noise Rejection
LOSS-OF-SIGNAL (Notes 2, 6)
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
CM_RSSI SPECIFICATION
RSSI Current Gain
V
CM
to I
RSSI
3dB Bandwidth
Input-Referred RSSI Current
Stability
RSSI Output Compliance Voltage
TTL/CMOS I/O
LOS Output High Voltage
LOS Output Low Voltage
V
OH
V
OL
R
LOS
= 4.7kΩ to 10kΩ to Vcc_host (3V)
R
LOS
= 4.7kΩ to 10kΩ to Vcc_host (3.6V)
2.4
0.4
V
V
I
RSSI
A
RSSI
V
RSSI
Input < 6.6mA, 0V
≤
V
RSSI
≤
2.5V (Note 9)
-40
0
A
RSSI
I
RSSI
/ I
CM_RSSI
(Note 8)
0.031
40
+36
2.0
kHz
µA
V
10 log (V
DEASSERT
/ V
ASSERT
)
(Note 7)
R
TH
= 2kΩ
R
TH
= 2kΩ
R
TH
= 14kΩ
R
TH
= 14kΩ
R
TH
= 25kΩ
R
TH
= 25kΩ
36
19.6
1.25
2.3
2.6
4
6
28
42
50
84
2.2
50
6.4
9.6
31.8
54.7
54.3
114
dB
µs
mV
P-P
mV
P-P
mV
P-P
mV
P-P
mV
P-P
mV
P-P
PSNR
f < 2MHz
SYMBOL
CONDITIONS
Input = 4mV
P-P
(Notes 2, 4)
4mV
P-P
<
V
INP-P
<
1200mV
P-P
,
20% to 80% (Note 2)
(Note 2)
20
35
29
41.5
35
MIN
TYP
3
70
MAX
7
114
150
UNITS
ps
RMS
ps
µV
RMS
kHz
MAX3746
mA
20
40
25
dB
_______________________________________________________________________________________
3
Low-Power, 622Mbps to 3.2Gbps
Limiting Amplifier
MAX3746
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +2.97V to +3.63V, CML output load is 50Ω to V
CC
, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at V
CC
=
+3.3V, T
A
= +25°C, unless otherwise specified. The data input transition time is controlled by 4th-order Bessel filter with f
-3dB
= 0.75 x
2.667GHz for all data rates of 2.667Gbps and below, and with f
-3dB
= 0.75 x 3.2GHz for a data rate of 3.2Gbps.)
PARAMETER
DISABLE Input High
DISABLE Input Low
DISABLE Input Current
SYMBOL
V
IH
V
IL
R
LOS
= 4.7kΩ to 10kΩ to Vcc_host
CONDITIONS
MIN
2.0
0.8
10
TYP
MAX
UNITS
V
V
µA
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
Note 8:
Note 9:
Between sensitivity and overload, all AC specifications are met.
Guaranteed by design and characterization.
The deterministic jitter caused by the filter is not included in the DJ generation specification.
Random jitter was measured without using a filter at the input.
The supply current measurement excludes the CML output currents by connecting the CML outputs to a separate V
CC
. (See
Figure 1.)
Hysteresis is calculated as 10 log (V
DEASSERT
/ V
ASSERT
). Unless otherwise specified, the data rate for all LOS detect speci-
fications varies from 622Mbps up to 3.2Gbps, and the patterns are 1010 or 2
23
- 1 PRBS.
The signal is switched between two amplitudes, Signal_On and Signal _Off as shown in Figure 2.
I
CM_RSSI
is the input common-mode current. I
RSSI
is the current at the RSSI output.
Stability is defined as the variation over temperature and power supply with respect to the typical gain of the part.
Typical Operating Characteristics
(V
CC
= +3.3V, T
A
= +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. TEMPERATURE
MAX3746 toc01
TRANSFER FUNCTION
MAX3746 toc02
RANDOM JITTER vs. TEMPERATURE
(INPUT LEVEL 10mV
P-P
)
9
8
RANDOM JITTER (ps
RMS
)
7
6
5
4
3
2
1
0
MAX3746 toc03
100
90
80
70
CURRENT (mA)
60
50
40
30
20
10
0
CML OUTPUTS NOT INCLUDED
CML OUTPUTS INCLUDED
OUTPOL = V
CC
900
800
DIFFERENTIAL OUTPUT (mV
P-P
)
700
600
500
400
300
200
100
0
0
1
2
3
4
5
6
OUTPOL = V
CC
10
-40 -30-20 -10 0 10 20 30 40 50 60 70 80 90 100
TEMPERATURE (°C)
-40 -30-20 -10 0 10 20 30 40 50 60 70 80 90 100
TEMPERATURE (°C)
DIFFERENTIAL INPUT (mV
P-P
)
4
_______________________________________________________________________________________
Low-Power, 622Mbps to 3.2Gbps
Limiting Amplifier
Typical Operating Characteristics (continued)
(V
CC
= +3.3V, T
A
= +25°C, unless otherwise noted.)
DETERMINISTIC JITTER
vs. INPUT COMMON-MODE VOLTAGE
(2.7Gbps, K28.5)
MAX3746 toc05
MAX3746
RANDOM JITTER
vs. INPUT AMPLITUDE
MAX3746 toc04
BIT-ERROR RATIO
vs. INPUT VOLTAGE
1200
1000
BIT-ERROR RATIO (10
-12
)
800
600
400
200
0
24
DETERMINISTIC JITTER (ps
P-P
)
22
20
18
16
14
12
10
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
INPUT VOLTAGE (mV
P-P
)
9
8
RANDOM JITTER (ps
RMS
)
7
6
5
4
3
2
1
0
0
5
10
15
20
25
30
35
40
-1.0 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0
COMMON-MODE VOLTAGE (V
CC
+ X)
DIFFERENTIAL INPUT (mV
P-P
)
OUTPUT EYE DIAGRAM
(MINIMUM INPUT)
MAX3746 toc07
OUTPUT EYE DIAGRAM
(MAXIMUM INPUT)
MAX3746 toc08
OUTPUT EYE DIAGRAM
(MINIMUM INPUT)
MAX3746 toc09
3.2Gbps, K28.5, 4mV
P-P
3.2Gbps, K28.5, 1200mV
P-P
2.7Gbps, 2
23
- 1 PRBS, 4mV
P-P
100mV/div
100mV/div
100mV/div
50ps/div
50ps/div
100ps/div
OUTPUT EYE DIAGRAM
(MAXIMUM INPUT)
MAX3746 toc10
OUTPUT EYE DIAGRAM AT +100°C
(MINIMUM INPUT)
MAX3746 toc11
ASSERT/DEASSERT LEVELS vs. R
TH
MAX3726 toc12
120
LOS ASSERT/DEASSERT (mV
P-P
)
100
80
60
40
20
0
DEASSERT
2.7Gbps, 2
23
- 1 PRBS, 1200mV
P-P
2.7Gbps, 2
23
- 1 PRBS, 4mV
P-P
100mV/div
100mV/div
ASSERT
50ps/div
50ps/div
0
10
R
TH
(kΩ)
20
30
_______________________________________________________________________________________
MAX3746 toc06
10
5
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