19-1999; Rev 4; 7/04
3.2Gbps Adaptive Equalizer
The MAX3801 is a +3.3V adaptive cable equalizer
designed for coaxial and twin-axial cable point-to-point
communications applications. The equalizer includes
differential CML data inputs and outputs, a loss-of-signal (LOS) output, and a cable integrity monitor (CIM)
output.
The adaptive cable equalizer is capable of equalizing
differential or single-ended signals at data rates up to
3.2Gbps. It automatically adjusts to attenuation caused
by skin-effect losses of up to 30dB at 1.6GHz. The
equalizer effectively extends the usable length of copper cable in high-frequency interconnect applications.
The MAX3801 is available in a 24-pin QFN package
with exposed pad and consumes only 125mW at
+3.3V.
Applications
Features
♦ Single +3.3V Operation
♦ Typical Power Dissipation = 125mW at +3.3V
♦ Data Rates Up to 3.2Gbps
♦ Equalizer Automatically Adjusts for Different
Cable Lengths
♦ 0dB to 30dB Equalization at 1.6GHz (3.2Gbps)
♦ Loss-of-Signal (LOS) Indicator
♦ Cable Integrity Monitor (CIM)
♦ On-Chip Input and Output Terminations
♦ Low External Component Count
♦ Operating Temperature Range = 0°°C to +85°°C
♦ ESD Protection on Inputs and Outputs
High-Speed Links in Communications
and Data Systems
Ordering Information
Backplane and Interconnect Applications
SDH/SONET Transmission Equipment
TEMP
RANGE
PART
PINPACKAGE
PACKAGE
CODE
MAX3801UGG
0°C to +85°C
24 QFN
G2444-1
MAX3801UTG
0°C to +85°C
24 Thin QFN
T2444-2
MAX3801UTG+
0°C to +85°C
24 Thin QFN
T2444-2
+Denotes lead-free package.
Pin Configuration appears at end of data sheet.
Typical Application Circuit
+3.3V
EOUT
LOS
CIM
CARD 1
+3.3V
CARD 2
MAX3801
EIN
MAX3801
EOUT
EIN
LOS
CIM
THIS SYMBOL INDICATES A CONTROLLED-IMPEDANCE TRANSMISSION LINE.
________________________________________________________________ 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
MAX3801
General Description
MAX3801
3.2Gbps Adaptive Equalizer
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VCC..............................................-0.5V to +6.0V
Voltage at LOS, CIM+, CIM-.......................-0.5V to (VCC + 0.5V)
Voltage at EIN+, EIN- .........................(VCC - 1V) to (VCC + 0.5V)
Current Out of EOUT+, EOUT-............................................25mA
Continuous Power Dissipation (TA = +85°C)
24-Lead QFN-EP (derate 25.1mW/°C above +85°C) .1630mW
Operating Ambient Temperature Range ................0°C to +85°C
Storage Temperature Range .............................-55°C to +150°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.
DC ELECTRICAL CHARACTERISTICS
(VCC = +3.14V to +3.46V, TA = 0°C to +85°C. Typical values are at VCC = +3.3V and TA = +25°C, unless otherwise noted.)
PARAMETER
Supply Current
SYMBOL
ICC
CONDITIONS
MIN
Includes external load current
TYP
MAX
UNITS
37
60
mA
650
700
MVP-P
INPUT SPECIFICATIONS
Minimum Cable Input (Differential)
3.2Gbps, 30dB cable loss at 1.6GHz (Note 1)
Maximum Cable Input (Differential)
1100
Input Impedance
mVP-P
62.5
Ω
1000
mVP-P
75
Ω
-0.5
+0.5
VP-P
No external load
0.5
VCC
- 0.5
V
Output high (Note 3)
2.4
Single-ended
40
Output Voltage (Differential)
(Note 2)
500
Output Impedance
Single-ended
50
53
OUTPUT SPECIFICATIONS
Voltage at CIM Output (Differential)
Voltage at CIM Output
(Single-Ended)
Voltage at LOS
Output Common-Mode Voltage
2
VCIM
VCIM+,
VCIM-
No external load, VCIM = (VCIM+) - (VCIM-)
65
Output low (Note 3)
Each output DC-coupled 50Ω to VCC
0.4
VCC - 0.2
_______________________________________________________________________________________
V
V
3.2Gbps Adaptive Equalizer
(VCC = +3.14V to +3.46V, TA = 0°C to +85°C. Typical values are at VCC = +3.3V and TA = +25°C, unless otherwise noted.) (Note 4)
PARAMETER
SYMBOL
CONDITIONS
TYP
MAX
0dB cable loss (Note 6)
120
240
24dB cable loss (Note 6)
140
240
30dB cable loss (Note 6)
100
200
Output Edge Speed
20% to 80%
64
90
Input Return Loss (Single-Ended)
≤3.2GHz
15
dB
Output Return Loss (Single-Ended)
≤3.2GHz
15
dB
Equalization Compensation
1.6GHz (skin-effect losses only)
Maximum Input Data Rate
Residual Jitter (Note 5)
Equalization Time Constant
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
MIN
3.2
UNITS
Gbps
30
mUIP-P
ps
dB
5
µs
Minimum cable input for LOS to assert high.
Input voltage within specification limits, 50Ω to VCC at each output.
100kΩ load to ground.
AC electrical characteristics are guaranteed by design and characterization.
Includes random jitter and deterministic jitter.
Differential cable input voltage = 700mVP-P, 3.2Gbps 213 - 1PRBS with 100 consecutive ones and 100 consecutive zeros
substituted. Cable loss is due to skin effect only.
_______________________________________________________________________________________
3
MAX3801
AC ELECTRICAL CHARACTERISTICS
Typical Operating Characteristics
(VCC = +3.3V, all jitter measurements done at 3.2Gbps, 700mV cable input with 213 - 1 PRBS pattern with 100 consecutive ones and
100 consecutive zeros substituted, TA = +25°C. Note: Test pattern produces near worst-case jitter results. Results vary with pattern,
unless otherwise noted.)
EQUALIZER RESIDUAL JITTER
vs. POWER-SUPPLY NOISE
(100mVP-P SINE WAVE)
(85FT OF GORE 89 CABLE)
MAX3801 toc02
50
130
100FT
120
JITTER (psP-P)
MAX3801 toc01
40
JITTER (psP-P)
SUPPLY CURRENT (mA)
60
EQUALIZER RESIDUAL JITTER vs. INPUT
AMPLITUDE AT 3.2GHz (RG59 – 75Ω
COAXIAL CABLE – SINGLE-ENDED)
40
35
MAX3801 toc03
SUPPLY CURRENT vs. TEMPERATURE
45
110
100
90
288FT
80
70
188FT
10
20
30 40 50 60 70
TEMPERATURE (°C)
80
90
10
100
0
200
100
90
80
JITTER (psP-P)
2.5Gbps
1.2Gbps
50
2.5Gbps
1200
200
180
160
2.5Gbps
140
3.2Gbps
70
400
600
800 1000
INPUT AMPLITUDE (mVp-p)
EQUALIZER RESIDUAL JITTER
vs. CABLE LENGTH
(CATEGORY 5E – TWISTED PAIR)
INPUT LEVEL OF 700mVP-P
MAX3801 toc05
3.2Gbps
70
60
1
EQUALIZER RESIDUAL JITTER
vs. CABLE LENGTH (RG179B – 75Ω
COAXIAL CABLE – SINGLE-ENDED)
INPUT LEVEL OF 700mVP-P
MAX3801 toc04
100
80
0.1
NOISE FREQUENCY (MHz)
EQUALIZER RESIDUAL JITTER
vs. CABLE LENGTH (RG59 – 75Ω COAXIAL
CABLE – SINGLE-ENDED)
INPUT LEVEL OF 500mVP-P
90
0.01
JITTER(psP-P)
0
60
MAX3801 toc06
30
0.001
30
JITTER (psP-P)
MAX3801
3.2Gbps Adaptive Equalizer
1.2Gbps
60
50
3.2Gbps
120
1.2Gbps
100
80
622Mbps
60
40
40
30
622Mbps
40
20
20
20
100 120 140 160 180 200 220 240 260 280 300
CABLE LENGTH (ft)
4
622Mbps
30
0
25
35
45
55
CABLE LENGTH (ft)
65
75
5
15
25 35 45 55 65
CABLE LENGTH (ft)
_______________________________________________________________________________________
75
85 95
3.2Gbps Adaptive Equalizer
100
EQUALIZER OUTPUT EYE DIAGRAM
AFTER 288 FT OF RG59 CABLE
(INPUT OF 1000mVP-P, 3.2Gbps, 223 - 1PRBS)
MAX3801 toc09
MAX3801 toc07
110
EQUALIZER INPUT AFTER
115FT OF CABLE (TOP)
EQUALIZER OUTPUT (BOTTOM)
MAX3801 toc08
EQUALIZER RESIDUAL JITTER vs. LINE LENGTH
(FR-4 6MIL STRIPLINE – SINGLE-ENDED)
80
70
622Mbps
3.2Gbps
2.5Gbps
60
50
40
85 (in)
2.16 (m)
EQUALIZER OUTPUT EYE DIAGRAM
AFTER 100FT OF 75Ω RG179 CABLE
(2.5Gbps, SINGLE-ENDED, 27 - 1PRBS)
EQUALIZER OUTPUT EYE DIAGRAM
AFTER 115FT OF 50Ω GORE 89 CABLE
(INPUT OF 1000mVP-P, 3.2Gbps)
MAX3801 toc11
MAX3801 toc10
EQUALIZER OUTPUT EYE DIAGRAM
AFTER 70FT OF CATEGORY 5E CABLE
(INPUT OF 1000mVP-P, 1.25Gbps)
MAX3801 toc12
40 45 50 55 60 65 70 75 80
1.02 1.14 1.27 1.40 1.52 1.65 1.77 1.90 2.03
LINE LENGTH
68ps/div
50ps/div
200ps/div
EQUALIZER INPUT RETURN LOSS (S11)
EQUALIZER OUTPUT RETURN LOSS (S22)
40
30
40
30
20
10
10
GAIN (dB)
20
0
-10
0
-10
-20
-20
-30
-30
-40
-40
-50
MAX3801 toc15
50
MAX3801 toc14
50
GAIN (dB)
JITTER (psp-p)
90
-50
0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0
FREQUENCY (GHz)
0
0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0
FREQUENCY (GHz)
_______________________________________________________________________________________
5
MAX3801
Typical Operating Characteristics (continued)
(VCC = +3.3V, all jitter measurements done at 3.2Gbps, 700mV cable input with 213 - 1 PRBS pattern with 100 consecutive ones and
100 consecutive zeros substituted, TA = +25°C. Note: Test pattern produces near worst-case jitter results. Results vary with pattern,
unless otherwise noted.)
3.2Gbps Adaptive Equalizer
MAX3801
Pin Description
PIN
NAME
FUNCTION
1, 3, 7, 12, 16, 18,
19, 24
GND
Ground
2, 4, 8, 11, 17, 20,
23
VCC
Power Supply
5
CIM-
Negative Cable Integrity Monitor (CIM) Output
6
CIM+
Positive Cable Integrity Monitor (CIM) Output
9
EOUT-
Negative Equalizer Output, CML
10
EOUT+
Postive Equalizer Output, CML
13, 14
N.C.
No connection. Leave unconnected.
15
LOS
Equalizer Loss-of-Signal Output, Active-Low
21
EIN+
Postive Equalizer Input, CML
22
EIN-
Negative Equalizer Input, CML
EP
Exposed Pad
Ground. The exposed pad must be soldered to the circuit board ground for proper
thermal and electrical operation.
Detailed Description
The adaptive cable equalizer accepts differential CML
input data at rates up to 3.2Gbps and is capable of
equalizing differential or single-ended signals. It automatically adjusts to attenuation levels of up to 30dB at
1.6GHz (because of skin-effect losses in copper cable).
The equalizer consists of a CML input buffer, a loss-ofsignal detector, a flat response amplifier, a skin-effect
compensation amplifier, a current-steering network, a
dual power-detector feedback loop, an output limiting
amplifier, and a CML output buffer (Figure 1).
General Theory of Operation
The shape of the power spectrum of a random bit
stream can be described by the square of the sinc
function, where sinc f = (sin πf) / πf. For sufficiently long
bit patterns (nonrandom bit streams), sinc2(f) is a good
approximation. From the shape of the sinc2(f) function,
we can estimate the ratio of the power densities at any
two frequencies. The MAX3801 adaptive equalizer
employs this principle by incorporating a feedback loop
that continuously monitors the power at two frequencies
and dynamically adjusts the equalizer to maintain the
correct power ratio.
6
CML Input and Output Buffers
The input and output buffers are implemented using
current-mode logic (CML). Equivalent circuits are
shown in Figures 2 and 3. For details on interfacing with
CML, refer to Maxim application note HFAN-1.0,
Introduction to LVDS, PECL, and CML.
Flat Response and Skin-Effect
Compensation Amplifiers
The buffered input waveform is fed equally to two
amplifiers—the flat response amplifier and the skineffect compensation amplifier. The flat response amplifier has a constant gain over the entire frequency range
of the device, and the skin-effect compensation amplifier has a gain characteristic that approximates the
inverse of the skin-effect attenuation inherent in copper
cable. The skin-effect attenuation, in dB per unit length,
is proportional to the square root of the frequency. The
output currents from the two amplifiers are supplied to
the current-steering network. Note that, when LOS
asserts low, equalization is minimized.
Current-Steering Network
The function of the current-steering network is to combine adjustable quantities of the output currents from
the flat response and skin-effect compensation ampli-
_______________________________________________________________________________________
CIM-
MAX3801
CIM+
3.2Gbps Adaptive Equalizer
200MHz
PWR DETECTOR
FLAT
RESPONSE
AMP
600MHz
PWR DETECTOR
LOOP
FILTER
|H(f)|
VARIABLE
ATTENUATOR
|H(f)|
EIN
Σ
√f
CML
SKIN
EFFECT
COMPENSATION
AMP
P0WER
DETECTOR
LIMITING
AMP
CML
EOUT
VARIABLE
ATTENUATOR
CURRENT STEERING NETWORK
MAX3801
LOS
Figure 1. Functional Diagram
VCC
VCC
ESD
STRUCTURES
62.5Ω
50Ω
62.5Ω
50Ω
EOUT+
EIN+
EOUT-
EIN-
ESD
STRUCTURES
GND
GND
Figure 2. CML Input Equivalent Circuit
Figure 3. CML Output Equivalent Circuit
_______________________________________________________________________________________
7
VCC
GND
24
23
22
21
20
19
GND
1
18
GND
VCC
2
17
VCC
GND
3
16
GND
VCC
4
15
LOS
CIM-
5
14
N.C.
CIM+
6
13
N.C.
8
9
10
11
12
GND
7
VCC
MAX3801*
EOUT+
The differential CIM output current is directly proportional to the output current of the loop amplifier (which
controls the current-steering network—see the Detailed
Description). This is an analog current output that indicates the amount of equalization being applied. A convenient way to monitor the CIM current is to connect a
100kΩ resistor from each of the CIM outputs to ground,
and then measure the voltage at the CIM pins.
The amount of equalization (and thus the CIM output
level) is affected by various factors, including cable
type, cable length, signal bandwidth, etc.
EIN+
TOP VIEW
Cable Integrity Monitor (CIM)
EIN-
Pin Configuration
EOUT-
Applications Information
Refer to Maxim application note HFAN-10.0, Equalizing
Gigabit Copper Cable Links with the MAX3800 (available at www.maxim-ic.com) for additional applications
information.
Layout Considerations
The MAX3801’s performance significantly can be
affected by circuit-board layout and design. Use good
high-frequency design techniques, including minimizing ground inductance and using fixed-impedance
transmission lines for the high-frequency data signals.
Place power-supply decoupling capacitors as close as
possible to VCC.
VCC
Output Limiting Amplifier
The output limiting amplifier amplifies the signal from
the current-steering network to achieve the specified
output voltage swing.
Single-Ended Operation
For single-ended operation of the equalizer, connect
the unused input to ground through a series combination of a capacitor (of equal value to other AC-coupling
capacitors) and a 50Ω resistor. Note that the MAX3801
is specified for differential operation. The effective
range of equalization for single-ended use is approximately 4dB to 30dB at 1.6GHz.
VCC
Dual Power-Detector Feedback Loop
The output of the current-steering network is applied to
the inputs of two frequency-specific power detectors.
One of the power detectors is tuned to 200MHz, and
the other is tuned to 600MHz. The outputs of the two
power detectors are applied to the inverting (200MHz
power detector) and noninverting (600MHz power
detector) inputs of the differential loop amplifier. The
differential outputs of the loop amplifier control the variable attenuators in the current-steering network.
Loss-of-Signal (LOS) Output
Loss-of-signal is indicated by the LOS output. A low
level on LOS indicates that the equalizer input signal
power has dropped below a threshold. The LOS output
indicates a loss of signal. When the equalizer no longer
detects a signal from the channel, the LOS output goes
low. When there is sufficient input voltage to the channel (typically greater than 650mV), LOS is high. The
LOS output is suitable for indicating problems with the
transmission link caused by, for example, a broken
cable, a defective driver, or a lost connection to the
equalizer.
GND
fiers to achieve a desired current ratio. The ratio adjustment is controlled by the dual power-detector feedback
loop.
The current-steering network is implemented with two
variable attenuators that feed into a current-summing
node. The variable attenuators attenuate the output currents of the flat response and skin-effect compensation
amplifiers under control of the dual power-detector
feedback loop. The outputs of the two attenuators are
combined at the summing node and then fed to the output limiting amplifier and the feedback loop.
GND
MAX3801
3.2Gbps Adaptive Equalizer
QFN
*THE EXPOSED PAD MUST BE
SOLDERED TO THE SUPPLY GROUND.
8
_______________________________________________________________________________________
3.2Gbps Adaptive Equalizer
12,16,20, 24L QFN.EPS
PACKAGE OUTLINE
12,16,20,24L QFN, 4x4x0.90 MM
21-0106
E
1
2
PACKAGE OUTLINE
12,16,20,24L QFN, 4x4x0.90 MM
21-0106
E
2
2
_______________________________________________________________________________________
9
MAX3801
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.)
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.)
24L QFN THIN.EPS
MAX3801
3.2Gbps Adaptive Equalizer
PACKAGE OUTLINE,
12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm
21-0139
E
1
2
PACKAGE OUTLINE,
12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm
21-0139
E
2
2
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.
10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2004 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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