19-4360; Rev 0; 10/08
IT
TION K
VALUA
E
BLE
AVAILA
1.0625Gbps to 10.32Gbps, Integrated, Low-
Power SFP+ Limiting Amplifier and VCSEL Driver
General Description
The MAX3798 is a highly integrated limiting amplifier
and VCSEL driver designed for 1x/2x/4x/8x Fibre
Channel transmission systems at data rates up to
8.5Gbps as well as for 10GBASE-SR transmission sys-
tems at a data rate of 10.3125Gbps. Operating from a
single +3.3V supply, this low-power integrated limiting
amplifier and VCSEL driver IC enables a platform
design for SFP MSA as well as for SFP+ MSA-based
optical transceivers. The high-sensitivity limiting ampli-
fier limits the differential input signal generated by a
transimpedance amplifier into a CML-level differential
output signal. The compact VCSEL driver provides a
modulation and a bias current for a VCSEL diode. The
optical average power is controlled by an average
power control (APC) loop implemented by a controller
that interfaces to the VCSEL driver through a 3-wire
digital interface. All differential I/Os are optimally back-
terminated for a 50Ω transmission line PCB design.
The use of a 3-wire digital interface reduces the pin
count while enabling advanced Rx (mode selection,
LOS threshold, LOS squelch, LOS polarity, CML output
level, signal path polarity, slew-rate control, deempha-
sis, and fast mode-select change time) and Tx settings
(modulation current, bias current, polarity, programma-
ble deemphasis, eye-crossing adjustment, and eye
safety control) without the need for external compo-
nents. The MAX3798 provides multiple current and volt-
age DACs to allow the use of low-cost controller ICs.
The MAX3798 is packaged in a lead-free, 5mm x 5mm,
32-pin TQFN package.
Features
♦
Low Power Dissipation of 320mW at 3.3V Power
Supply
♦
Up to 10.32Gbps (NRZ) Operation
♦
3mV
P-P
Receiver Sensitivity at 10.32Gbps
♦
4ps
P-P
DJ at Receiver Output at 8.5Gbps 8B/10B
♦
4ps
P-P
DJ at Receiver Output at 10.32Gbps
2
31
- 1 PRBS
♦
26ps Rise and Fall Time at Rx/Tx Output
♦
Mode Select for High-Gain Mode and High-
Bandwidth Mode
♦
CML Output Slew-Rate Adjustment for High-Gain
Mode
♦
CML Output with Continuous Level Adjustment
♦
CML Output Squelch
♦
Polarity Select for Rx and Tx
♦
LOS Assert Level Adjustment
♦
LOS Polarity Select
♦
Modulation Current Up to 12mA Into 100Ω
Differential Load
♦
Bias Current Up to 15mA
♦
Integrated Eye Safety Features
♦
Selectable Deemphasis at Rx Output
♦
3-Wire Digital Interface
♦
Eye-Crossing Adjustment of Modulation Output
♦
Programmable Deemphasis at Tx Output
♦
Fast Mode-Select Change Time of 10µs
MAX3798
Applications
10GBASE-SR SFP+ Optical Transceiver
1x/2x/4x/8x SFF/SFP/SFP+ MSA Fibre Channel
(FC) Optical Transceiver
10GBASE-LR SFP+ Optical Transceiver (1310nm
VCSEL)
10GBASE-LRM SFP+ Optical Transceiver
(1310nm VCSEL)
Ordering Information
PART
MAX3798ETJ+
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
32 TQFN-EP*
+Denotes
a lead-free/RoHS-compliant package.
*EP
= Exposed pad.
Typical Application Circuit and Pin Configuration appear at
end of data sheet.
________________________________________________________________
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.
1.0625Gbps to 10.32Gbps, Integrated, Low-
Power SFP+ Limiting Amplifier and VCSEL Driver
MAX3798
ABSOLUTE MAXIMUM RATINGS
V
CCR
, V
CCT
, V
CCD
.................................................-0.3V to +4.0V
Voltage Range at DISABLE, SDA, SCL,
CSEL, MSEL, FAULT, BMON, LOS,
BMAX, MMAX, CAZ2...............................-0.3V to (V
CC
+ 0.3V)
Voltage Range at ROUT+, ROUT- .....(V
CC
- 1V) to (V
CC
+ 0.3V)
Voltage at TIN+, TIN-........................(V
CC
- 2.5V) to (V
CC
- 0.5V)
Voltage Range at TOUT+, TOUT- ......(V
CC
- 2V) to (V
CC
+ 0.3V)
Voltage at BIAS...............................................................0 to V
CC
Voltage at RIN+, RIN- ..........................(V
CC
- 2V) to (V
CC
- 0.2V)
Current Range into FAULT, LOS...........................-1mA to +5mA
Current Range into SDA........................................-1mA to +1mA
Current into ROUT+, ROUT- ...............................................40mA
Current into TOUT+, TOUT- ................................................60mA
Continuous Power Dissipation (T
A
= +70°C)
32-Pin TQFN (derate 34.5W/°C above +70°C) ...........2759mW
Operating Junction Temperature Range ...........-55°C to +150°C
Storage Temperature Range .............................-65°C to +160°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
= 2.85V to 3.63V, T
A
= -40°C to +85°C, CML receiver output load is AC-coupled to differential 100Ω, C
AZ
= 1nF, transmitter out-
put load is AC-coupled to differential 100Ω (see Figure 1), typical values are at +25°C, V
CC
= 3.3V, I
BIAS
= 6mA, I
MOD
= 6mA, unless
otherwise specified. Registers are set to default values unless otherwise noted, and the 3-wire interface is static during measure-
ments. For testing, the MODE_SEL bit was used and the MSEL pin was left open.)
PARAMETER
POWER SUPPLY
Power-Supply Current
I
CC
V
CC
Includes the CML output current;
excludes I
BIAS
= 6mA, I
MOD
= 6mA,
V
DIFF_ROUT
= 400mV
P-P
(Note 1)
2.85
1.0625
14.1
10E-12
2.55
I
BIAS
= I
BIASOFF
and I
MOD
= I
MODOFF
2.3
2.45
2.75
V
V
97
150
3.63
10.32
mA
V
Gbps
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Power-Supply Voltage
GENERAL
Input Data Rate
Input/Output SNR
BER
POWER-ON RESET
High POR Threshold
Low POR Threshold
Rx INPUT SPECIFICATIONS
Differential Input Resistance
RIN+/RIN-
Input Sensitivity (Note 2)
Input Overload
Input Return Loss
Input Return Loss
Rx OUTPUT SPECIFICATIONS
Differential Output Resistance
Output Return Loss
R
IN_DIFF
V
INMIN
V
INMAX
SDD11
SCC11
DUT is powered on, f
DUT is powered on, f
5GHz
16GHz
5GHz
16GHz
MODE_SEL = 0 at 4.25Gbps
MODE_SEL = 1 at 8.5Gbps
75
100
2
3
125
4
8
mV
P-P
V
P-P
1.2
14
7
8
8
75
DUT is powered on, f
DUT is powered on, f
5GHz
16GHz
100
11
5
125
dB
dB
DUT is powered on, 1GHz < f
DUT is powered on, 1GHz < f
R
OUTDIFF
SDD22
dB
2
_______________________________________________________________________________________
1.0625Gbps to 10.32Gbps, Integrated, Low-
Power SFP+ Limiting Amplifier and VCSEL Driver
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 2.85V to 3.63V, T
A
= -40°C to +85°C, CML receiver output load is AC-coupled to differential 100Ω, C
AZ
= 1nF, transmitter out-
put load is AC-coupled to differential 100Ω (see Figure 1), typical values are at +25°C, V
CC
= 3.3V, I
BIAS
= 6mA, I
MOD
= 6mA, unless
otherwise specified. Registers are set to default values unless otherwise noted, and the 3-wire interface is static during measure-
ments. For testing, the MODE_SEL bit was used and the MSEL pin was left open.)
PARAMETER
Output Return Loss
CML Differential Output Voltage
High
CML Differential Output Voltage
Medium
Differential Output Signal When
Disabled
SYMBOL
SCC22
CONDITIONS
DUT is powered on, 1GHz < f
DUT is powered on, 1GHz < f
5mV
P-P
10mV
P-P
V
IN
V
IN
5GHz
16GHz
595
300
MIN
TYP
9
7
800
400
1005
515
MAX
UNITS
dB
mV
P-P
mV
P-P
mV
P-P
MAX3798
1200mV
P-P
, SET_CML[162]
1200mV
P-P
, SET_CML[80]
Outputs AC-coupled, V
INMAX
applied to
input V
DIFF_ROUT
= 800mV
P-P
at 8.5Gbps
(Notes 2, 3)
10mV
P-P
V
IN
1200mV
P-P
,
MODE_SEL = 1, V
DIFF_ROUT
= 400mV
P-P
6
15
26
35
Data Output Transition Time
(20% to 80%)
(Notes 2, 3, 4)
t
R
/t
F
5mV
P-P
V
IN
1200mV
P-P
,
MODE_SEL = 0, SLEW_RATE = 1,
V
DIFF_ROUT
= 800mV
P-P
5mV
P-P
V
IN
1200mV
P-P
,
MODE_SEL = 0, SLEW_RATE = 0,
V
DIFF_ROUT
= 800mV
P-P
28
50
ps
45
Rx TRANSFER CHARACTERISTICS
60mV
P-P
V
IN
400mV
P-P
at 10.32Gbps,
MODE_SEL = 1, V
DIFF_ROUT
= 400mV
P-P
10mV
P-P
V
IN
1200mV
P-P
at 8.5Gbps,
MODE _SEL = 1, V
DIFF_ROUT
= 400mV
P-P
10mV
P-P
V
IN
1200mV
P-P
at 4.25Gbps,
MODE _SEL = 1, V
DIFF_ROUT
= 400mV
P-P
Deterministic Jitter
(Notes 2, 3, 5)
DJ
10mV
P-P
V
IN
1200mV
P-P
at 8.5Gbps,
MODE _SEL = 0, V
DIFF_ROUT
= 400mV
P-P
5mV
P-P
V
IN
1200mV
P-P
at 4.25Gbps,
MODE _SEL = 0, SLEW_RATE = 1,
V
DIFF_ROUT
= 800mV
P-P
5mV
P-P
V
IN
1200mV
P-P
at 4.25Gbps,
MODE _SEL = 0, SLEW_RATE = 0,
V
DIFF_ROUT
= 800mV
P-P
Input = 60mV
P-P
at 4.25Gbps
,
MODE_SEL = 0, V
DIFF_ROUT
= 800mV
P-P
Input = 60mV
P-P
at 8.5Gbps
,
MODE _SEL = 1, V
DIFF_ROUT
= 400mV
P-P
Low-Frequency Cutoff
Rx LOS SPECIFICATIONS
LOS Assert Sensitivity Range
LOS Hysteresis
10 x log(V
DEASSERT
/V
ASSERT
) (Note 6)
14
1.25
2.1
77
mV
P-P
dB
C
AZ
= 0.1μF
C
AZ
= open
4
4
5
5
10
ps
P-P
12
12
6
20
7
0.36
0.32
2
500
0.51
ps
RMS
0.48
kHz
Random Jitter (Notes 2, 3)
RJ
_______________________________________________________________________________________
3
1.0625Gbps to 10.32Gbps, Integrated, Low-
Power SFP+ Limiting Amplifier and VCSEL Driver
MAX3798
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 2.85V to 3.63V, T
A
= -40°C to +85°C, CML receiver output load is AC-coupled to differential 100Ω, C
AZ
= 1nF, transmitter out-
put load is AC-coupled to differential 100Ω (see Figure 1), typical values are at +25°C, V
CC
= 3.3V, I
BIAS
= 6mA, I
MOD
= 6mA, unless
otherwise specified. Registers are set to default values unless otherwise noted, and the 3-wire interface is static during measure-
ments. For testing, the MODE_SEL bit was used and the MSEL pin was left open.)
PARAMETER
LOS Assert/Deassert Time
Low Assert Level
Low Deassert Level
Medium Assert Level
Medium Deassert Level
High Assert Level
High Deassert Level
Tx INPUT SPECIFICATIONS
Differential Input Voltage
Common-Mode Input Voltage
Differential Input Resistance
Input Return Loss
Input Return Loss
Tx LASER MODULATOR
Maximum Modulation-On
Current into 100 Differential
Load
Minimum Modulation-On Current
into 100 Differential Load
Modulation Current DAC
Stability
Modulation Current Rise Time/
Fall Time
t
R
/t
F
I
MODMAX
Outputs AC-coupled, V
CCTO
2.95V
12
mA
V
IN
V
INCM
R
IN
SDD11
SCC11
DUT is powered on, f
DUT is powered on, f
5GHz
16GHz
5GHz
16GHz
75
Data rate = 1.0625Gbps to 4.25Gbps
Data rate = 4.25Gbps to 10.32Gbps
0.2
0.075
2.75
100
15
6
9
5
125
dB
dB
2.4
0.8
V
P-P
V
SYMBOL
(Note 7)
SET_LOS[7] (Notes 2, 6)
SET_LOS[7] (Notes 2, 6)
SET_LOS[32] (Notes 2, 6)
SET_LOS[32] (Notes 2, 6)
SET_LOS[63] (Notes 2, 6)
SET_LOS[63] (Notes 2, 6)
CONDITIONS
MIN
2.3
8
14
39
65
77
127
11
18
48
81
94
158
TYP
MAX
80
14
21
58
95
112
182
UNITS
μs
mV
P-P
mV
P-P
mV
P-P
mV
P-P
mV
P-P
mV
P-P
DUT is powered on, 1GHz < f
DUT is powered on, 1GHz < f
I
MODMIN
Outputs AC-coupled
2mA
I
MOD
12mA (Note 8)
26
2
4
39
mA
%
ps
5mA I
MOD
10mA, 20% to 80%,
SET_TXDE[3:0] = 10 (Notes 2, 4)
5mA I
MOD
12mA, at 10.32Gbps,
250mV
P-P
V
IN
800mV
P-P
,
SET_TXDE[3:0] = 0
5mA I
MOD
12mA, at 10.32Gbps,
250mV
P-P
V
IN
800mV
P-P
,
SET_TXDE[3:0] = 10
6
12
6
13
Deterministic Jitter (Notes 2, 9)
DJ
5mA I
MOD
12mA, at 8.5Gbps,
250mV
P-P
V
IN
800mV
P-P
,
SET_TXDE[3:0] = 0
5mA I
MOD
12mA, at 8.5Gbps,
250mV
P-P
V
IN
800mV
P-P
,
SET_TXDE[3:0] = 10
2mA
2mA
I
MOD
I
MOD
12mA, at 4.25Gbps
12mA, at 1.0625Gbps
6
12
ps
6
5
5
12
4
_______________________________________________________________________________________
1.0625Gbps to 10.32Gbps, Integrated, Low-
Power SFP+ Limiting Amplifier and VCSEL Driver
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 2.85V to 3.63V, T
A
= -40°C to +85°C, CML receiver output load is AC-coupled to differential 100Ω, C
AZ
= 1nF, transmitter out-
put load is AC-coupled to differential 100Ω (see Figure 1), typical values are at +25°C, V
CC
= 3.3V, I
BIAS
= 6mA, I
MOD
= 6mA, unless
otherwise specified. Registers are set to default values unless otherwise noted, and the 3-wire interface is static during measure-
ments. For testing, the MODE_SEL bit was used and the MSEL pin was left open.)
PARAMETER
Random Jitter
Output Return Loss
Tx BIAS GENERATOR
Maximum Bias-On Current
Minimum Bias-On Current
BIAS Current DAC Stability
Compliance Voltage at BIAS
BIAS Current Monitor Current
Gain
Compliance Voltage at BMON
BIAS Current Monitor Current
Gain Stability
Tx SAFETY FEATURES
Excessive Voltage at BMAX
V
BMAX
Average voltage, FAULT always occurs for
V
BMAX
V
CC
- 0.65V, FAULT never occurs
for V
BMAX
V
CC
- 0.55V
Average voltage, FAULT always occurs for
V
MMAX
V
CC
- 0.65V, FAULT never occurs
for V
MMAX
V
CC
- 0.55V
Average voltage, FAULT warning always
occurs for V
BMON
V
CC
- 0.55V, FAULT
warning never occurs for V
BMON
V
CC
-
0.65V
Average voltage, FAULT always occurs for
V
BIAS
0.44V, FAULT never occurs for
V
BIAS
0.65V
FAULT or DISABLE, V
BIAS
= V
CC
V
CC
-
0.65V
V
CC
-
0.6V
V
CC
-
0.55V
V
V
BIAS
I
BMON
V
BMON
I
BMON
2mA
I
BIAS
15mA (Note 10)
External resistor to GND defines the
voltage gain
0
I
BIASMAX
I
BIASMIN
Current into BIAS pin
Current into BIAS pin
2mA
I
BIAS
15mA (Notes 2, 10)
0.9
16
1.8
5
15
2
4
2.1
mA
mA
%
V
mA/A
V
%
SDD22
SYMBOL
5mA I
MOD
800mV
P-P
CONDITIONS
12mA, 250mV
P-P
5GHz
16GHz
V
IN
MIN
TYP
0.17
12
5
MAX
0.5
UNITS
ps
RMS
dB
MAX3798
DUT is powered on, f
DUT is powered on, f
Excessive Voltage at MMAX
V
MMAX
V
CC
-
0.65V
V
CC
-
0.6V
V
CC
-
0.55V
V
Excessive Voltage at BMON
V
BMON
V
CC
-
0.65V
V
CC
-
0.6V
V
CC
-
0.55V
V
Excessive Voltage at BIAS
Maximum VCSEL Current in Off
State
SFP TIMING REQUIREMENTS
Mode-Select Change Time
V
BIAS
0.44
0.48
0.65
V
I
OFF
25
μA
t_
MODESEL
Time from rising or falling edge at MSEL
until Rx output PWD falls below 10ps
Time from rising edge of DISABLE input
signal to I
BIAS
= I
BIASOFF
and I
MOD
=
I
MODOFF
10
μs
DISABLE Assert Time
t_
OFF
1
μs
_______________________________________________________________________________________
5
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