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19-1953; Rev 1; 11/01
3.2Gbps Adaptive Equalizer and Cable Driver
General Description
The MAX3800 is a +3.3V adaptive cable equalizer and cable driver implemented together on a single chip. It is designed for coaxial and twin-axial cable point-to-point communications applications. The driver features differential current-mode logic (CML) inputs and outputs as well as adjustable output amplitude. 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 MAX3800 is available in a 32-pin TQFP package with exposed pad and consumes only 200mW at +3.3V. The driver can be disconnected from the power supply when it is not needed, resulting in a 40% reduction in supply current. o Single +3.3V Operation o Typical Power Dissipation = 200mW at +3.3V o Data Rates Up to 3.2Gbps o Adjustable Cable Driver Output Amplitude o Equalizer Automatically Adjusts for Different Cable Lengths o 0dB to 30dB Equalization at 1.6GHz (3.2Gbps) o Loss-of-Signal (LOS) Indicator o Cable Integrity Monitor (CIM) o On-Chip Input and Output Terminations o Low External Component Count o Operating Temperature Range = 0C to +85C o ESD Protection on Cable Inputs and Outputs
Features
MAX3800
Applications
High-Speed Links in Communications and Data Systems Backplane and Interconnect Applications SDH/SONET Transmission Equipment
Pin Configuration appears at end of data sheet.
PART MAX3800UGJ MAX3800UHJ
Ordering Information
TEMP. RANGE 0C to +85C 0C to +85C PIN-PACKAGE 32 QFN 32 TQFP-EP*
*EP = exposed pad
Typical Application Circuit
+3.3V +3.3V
DIN CARD 1 MAX3800 EOUT LOS RMOD
DOUT
EIN MAX3800
EOUT CARD 2 DIN RMOD CIM
EIN CIM
DOUT LOS
THIS SYMBOL INDICATES A CONTROLLED-IMPEDANCE TRANSMISSION LINE.
________________________________________________________________ Maxim Integrated Products
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3.2Gbps Adaptive Equalizer and Cable Driver MAX3800
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VCC..............................................-0.5V to +6.0V Voltage at LOS, RMOD, and CIM...............-0.5V to (VCC + 0.5V) Voltage at EIN+, EIN-, DIN+, DIN- .....(VCC - 1V) to (VCC + 0.5V) Current Out of EOUT+, EOUT-, DOUT+, DOUT- ................25mA Continuous Power Dissipation (TA = +85C) 32-Pin TQFP-EP (derate 22.2mW/C above +85C) ...1444mW Operating Ambient Temperature Range ................0C to +85C Storage Temperature Range .............................-55C to +150C 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.
DC ELECTRICAL CHARACTERISTICS
(VCC = +3.14V to +3.46V, TA = 0C to +85C. Typical values are at VCC = +3.3V and TA = +25C, unless otherwise noted.)
PARAMETER Supply Current SYMBOL ICC VDIN+, VDINVDIN VDIN = (VDIN+) - (VDIN-) Single-ended RMOD = 10k (Note 2) RMOD = 20k (Note 2) Single-ended 3.2Gbps, 30dB cable loss at 1.6GHz (Note 3) Single-ended (Note 2) Single-ended VCIM VCIM+, VCIMNo external load, VCIM = (VCIM+) - (VCIM-) No external load Output high (Note 4) Output low (Note 4) Each output DC-coupled 50 to VCC VCC - 0.2 45 500 50 -0.5 0.5 2.4 0.4 62.5 CONDITIONS Includes external load current (Note 1) VCC - 0.6 400 45 750 400 50 55 870 450 62.5 650 1100 55 65 1000 75 +0.5 VCC - 0.5 MIN TYP 65 MAX 85 VCC + 0.2 1100 65 1000 550 75 700 UNITS mA
CABLE DRIVER INPUT SPECIFICATIONS Input Voltage (Single-Ended) Input Voltage (Differential) Input Impedance CABLE DRIVER OUTPUT SPECIFICATIONS Output Voltage (Differential) Output Impedance CABLE EQUALIZER INPUT SPECIFICATIONS Minimum Cable Input (Differential) Maximum Cable Input (Differential) Input Impedance Output Voltage (Differential) Output Impedance Voltage at CIM Output (Differential) Voltage at CIM Output (Single-Ended) Voltage at LOS Output Common-Mode Voltage CABLE EQUALIZER OUTPUT SPECIFICATIONS mVp-p Vp-p V V V V mVp-p mVp-p mVp-p mVp-p V mVp-p
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3.2Gbps Adaptive Equalizer and Cable Driver
AC ELECTRICAL CHARACTERISTICS
(VCC = +3.14V to +3.46V, TA = 0C to +85C. Typical values are at VCC = +3.3V and TA = +25C, unless otherwise noted.) (Note 5)
PARAMETER Maximum Input Data Rate CABLE DRIVER SPECIFICATIONS Random Jitter Deterministic Jitter Output Edge Speed Input Return Loss (Single-Ended) Output Return Loss (Single-Ended) EQUALIZER SPECIFICATIONS 0dB cable loss (Note 8) Residual Jitter (Note 7) Output Edge Speed Input Return Loss (Single-Ended) Output Return Loss (Single-Ended) Equalization Compensation Equalization Time Constant 24dB cable loss (Note 8) 30dB cable loss (Note 8) 20% to 80% 3.2GHz 3.2GHz 1.6GHz (skin-effect losses only) 30 5 170 97 112 56 14 14 240 200 200 77 mUIp-p mUIp-p mUIp-p ps dB dB dB s (Note 6) (Note 6) 20% to 80% 3.2GHz 3.2GHz 2 20 59 14 14 4 60 76 mUIRMS mUIp-p ps dB dB SYMBOL CONDITIONS MIN 3.2 TYP MAX UNITS Gbps
MAX3800
Note 1: Note 2: Note 3: Note 4: Note 5: Note 6:
Equalizer and driver total currents (equalizer with maximum equalization and driver with maximum output swing). Input voltage within specification limits, 50 to VCC at each output. Minimum cable input for LOS to assert high. 100k load to ground. AC electrical characteristics are guaranteed by design and characterization. VDIN = 400mVp-p to 1100mVp-p (differential), 10k RMOD 20k, 3.2Gbps 213-1 PRBS with 100 consecutive ones and 100 consecutive zeros substituted. Note 7: Includes random jitter and deterministic jitter. Note 8: Differential cable input voltage = 700mVp-p, 3.2Gbps 213-1 PRBS with 100 consecutive ones and 100 consecutive zeros substituted. Cable loss is due to skin effect only.
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3.2Gbps Adaptive Equalizer and Cable Driver MAX3800
Typical Operating Characteristics
(TA = +25C, 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. Note: Test pattern produces near worst-case jitter results. Results will vary with pattern, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE
MAX3800 toc01
CABLE DRIVER OUTPUT VOLTAGE vs. RMOD
MAX3800 toc02
DRIVER INPUT RETURN LOSS (S11)
40 30 20 GAIN (dB) 10 0 -10 -20 -30 -40 -50
MAX3800 toc03
70 65 60 SUPPLY CURRENT (mA) 55 50 45 40 35 30 25 20 0 10 20 30 40 50 60 70 80 DRIVER EQUALIZER DRIVER + EQUALIZER
1300 1200 DRIVER OUTPUT VOLTAGE (mV) 1100 1000 900 800 700 600 500 400
50
90
4
7
10
13 RMOD (k)
16
19
22
0
0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0 FREQUENCY (GHz)
TEMPERATURE (C)
DRIVER OUTPUT RETURN LOSS (S22)
MAX3800 toc04
40 30 20 GAIN (dB) 10 0 -10 -20 -30 -40 -50 0
MAX3800 toc05
130 120 25 FT
50 JITTER (psp-p)
45
JITTER (psp-p)
110 100 72 FT 90
40
35 80 30 0.001 70 0.01 0.1 1 10 100 NOISE FREQUENCY (MHz) 300 400 500 600 700 800 900 1000 1100 CABLE INPUT AMPLITUDE (mV)
0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0 FREQUENCY (GHz)
MAX3800 toc07
90 80 JITTER (psp-p) 70 60 2.5Gbps 50 40 30 20 10 3.05 20 6.1 30 40 9.14 12.19 CABLE LENGTH 3.2Gbps 622Mbps
MAX3800 toc08
140 120 100 80 60
2.5Gbps
100 90
JITTER (psp-p)
3.2Gbps
JITTER (psp-p)
80 70 60 50 2.5Gbps 3.2Gbps
622Mbps
622Mbps 50 (FEET) 15.24 (METERS) 40 25 35 45 55 65 75 85 95 (FEET) 7.65 10.67 13.72 16.76 19.81 22.86 25.91 28.96 (METERS) CABLE LENGTH
40
40 45 50 55 60 65 70 75 80 85 (INCHES) 1.02 1.14 1.27 1.40 1.52 1.65 1.77 1.90 2.03 2.16 (METERS) LINE LENGTH
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MAX3800 toc09
100
EQUALIZER RESIDUAL JITTER vs. CABLE LENGTH (MADISON #13887 SHIELDED TWISTED PAIR-DIFFERENTIAL)
160
EQUALIZER RESIDUAL JITTER vs. CABLE LENGTH (RG179B 75 COAXIAL CABLE - SINGLE-ENDED)
EQUALIZER RESIDUAL JITTER vs. LINE LENGTH (FR-4 6MIL STRIPLINE - SINGLE-ENDED)
110
MAX3800 toc06
50
EQUALIZER RESIDUAL JITTER vs. POWER SUPPLY NOISE (100mVp-p SINE WAVE) (40FT OF MADISON #14887 SHIELDED TWISTED PAIR-DIFFERENTIAL)
55 140
EQUALIZER RESIDUAL JITTER vs. CABLE INPUT AMPLITUDE (RG179B 75 COAXIAL CABLE - SINGLE-ENDED)
3.2Gbps Adaptive Equalizer and Cable Driver MAX3800
Typical Operating Characteristics (continued)
(TA = +25C, 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. Note: Test pattern produces near worst-case jitter results. Results will vary with pattern, unless otherwise noted.)
EQUALIZER INPUT AFTER 115FT OF CABLE (TOP) EQUALIZER OUTPUT (BOTTOM)
MAX3800 toc10
EQUALIZER OUTPUT EYE DIAGRAM AFTER 115FT OF 50 GORE 89 CABLE (DIFFERENTIAL, 27-1 PRBS)
MAX3800 toc11
EQUALIZER OUTPUT EYE DIAGRAM AFTER 100FT OF 75 RG179 CABLE (SINGLE-ENDED, 27-1 PRBS)
MAX3800 toc12
60ps/div (2.5Gbps)
68ps/div (2.5Gbps)
EQUALIZER OUTPUT EYE DIAGRAM AFTER 100FT OF BELDEN 9207 CABLE (DIFFERENTIAL, 27-1 PRBS)
MAX3800 toc13
EQUALIZER OUTPUT EYE DIAGRAM AFTER 50FT OF MADISON #14887 SHIELDED TWISTED PAIR CABLE (DIFFERENTIAL, 27-1 PRBS)
MAX3800 toc14
CIM VOLTAGE vs. CABLE LENGTH (RG179B 75 COAXIAL CABLE SINGLE-ENDED)
MAX3800 toc15
1.8 1.7 CIM VOLTAGE (V) 1.6 1.5 1.4 1.3 1.2 CIM+ CIM-
60ps/div (2.5Gbps)
60ps/div (2.5Gbps)
0
10 20 30 40 50 60 70 80 90 100 CABLE LENGTH (FEET)
EQUALIZER INPUT RETURN LOSS (S11)
MAX3800 toc16
EQUALIZER OUTPUT RETURN LOSS (S22)
40 30 20 GAIN (dB) 10 0 -10 -20 -30 -40 -50
MAX3800 toc17
50 40 30 20 GAIN (dB) 10 0 -10 -20 -30 -40 -50 0
50
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)
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3.2Gbps Adaptive Equalizer and Cable Driver MAX3800
Pin Description
PIN 1, 3, 6, 11, 14 2, 7, 10, 15, 23, 24, 26, 31 4 5 8 9 12 13 16, 17 18 19, 22, 27, 30, 32 20 21 25 28 29 EP NAME VCCE GND EIN+ EINCIMCIM+ EOUTEOUT+ N.C. LOS VCCD DIN+ DINRMOD DOUT+ DOUTExposed Pad Equalizer Power Supply Ground Positive Equalizer Input, CML Negative Equalizer Input, CML Negative Cable Integrity Monitor (CIM) Output Positive Cable Integrity Monitor (CIM) Output Negative Equalizer Output, CML Positive Equalizer Output, CML No Connection. Leave unconnected. Equalizer Loss-of-Signal Output, Active-Low Driver Power Supply Positive Driver Input, CML Negative Driver Input, CML Driver Output Modulation Adjust. A resistor connected from this pin to GND controls driver output voltage. Positive Driver Output, CML Negative Driver Output, CML Ground. The exposed pad must be soldered to the circuit board ground plane for proper thermal and electrical performance. FUNCTION
Detailed Description
The MAX3800 consists of a cable driver (transmitter) and an adaptive cable equalizer (receiver). The driver and equalizer are implemented on the same chip, but they are completely independent.
nal 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 f) / f. 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 MAX3800 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. 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
The Cable Driver
The cable driver accepts differential or single-ended current-mode logic (CML) input data at rates up to 3.2Gbps. The driver output is also implemented using CML. The maximum output amplitude can be adjusted over a typical range of 450mV to 870mV by changing the value of the RMOD resistor between 10k and 20k (this resistor is connected between the RMOD pin and ground).
The Adaptive Cable Equalizer
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 (due to skin-effect losses in copper cable). The equalizer consists of a CML input buffer, a loss-of-sig6
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3.2Gbps Adaptive Equalizer and Cable Driver MAX3800
CIM+ CIM-
|H(f)|
LOOP FILTER
FLAT RESPONSE AMP
VARIABLE ATTENUATOR
|H(f)| EIN CML f
VARIABLE ATTENUATOR CURRENT STEERING NETWORK
200MHz PWR DETECTOR
600MHz PWR DETECTOR
LIMITING AMP
CML
EOUT
P0WER DETECTOR
SKIN EFFECT COMPENSATION AMP
LOS DOUT CML CABLE DRIVER
MAX3800
CML DIN
RMOD
Figure 1. Functional Diagram
VCC VCC ESD STRUCTURES 62.5 50 IN+ OUT50 OUT+ 62.5
IN-
ESD STRUCTURES
GND GND
Figure 2. CML Input Equivalent Circuit
Figure 3. CML Output Equivalent Circuit
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3.2Gbps Adaptive Equalizer and Cable Driver MAX3800
CML, see Maxim application note HFAN-1.0, Interfacing Between CML, PECL, and LVDS. 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 amplifiers 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 a pair of variable attenuators that feed into a current-summing node. The variable attenuators are used to 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. 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. Output Limiting Amplifier The output limiting amplifier amplifies the signal from the current-steering network to achieve the specified output voltage swing.
Applications Information
Refer to Maxim application note HFDN-10.0, Equalizing Gigabit Copper Cable Links with the MAX3800 (available at www.maxim-ic.com) for additional applications information.
Selecting RMOD
The cable driver output amplitude can be adjusted by connecting a resistor with a value from 10k to 20k between the RMOD pin and ground. The exact output amplitude of the driver for a given value of RMOD resistance is dependent on a number of factors. Refer to the Typical Operating Characteristics "Cable Driver Output Voltage vs. RMOD" for typical values.
Cable Integrity Monitor (CIM)
The differential CIM output current is directly proportional to the output current of the loop amplifier (which controls the current-steering network--see Detailed Description). This is an analog current output that indicates the amount of equalization that is being applied. A convenient way to monitor the CIM current is to connect a 100k 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. Refer to the Typical Operating Characteristics "CIM Voltage vs. Cable Length" for typical values under specific conditions.
L 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 that 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.
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3.2Gbps Adaptive Equalizer and Cable Driver
Single-Ended Operation
For single-ended operation of the cable driver or equalizer, connect the unused input to ground through a series combination of a capacitor (of equal value to other AC-coupling capacitors) and a 50 resistor. Note that the MAX3800 is specified for differential operation.
MAX3800
Layout Considerations
The MAX3800's performance can be significantly 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. Power-supply decoupling capacitors should be placed as close as possible to VCC.
Pin Configuration
DOUT+
TOP VIEW
DOUTVCCD VCCD GND
32 VCCE GND VCCE EIN+ EINVCCE GND CIM1 2 3 4 5 6 7 8 9 CIM+
31
30
29
28
27
26
RMOD 25 24 GND 23 GND 22 VCCD 21 DIN20 DIN+ 19 VCCD 18 LOS 17 N.C. 16 N.C.
VCCD 14 VCCE
MAX3800
10 GND
11 VCCE
12 EOUT-
13 EOUT+
15 GND
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GND
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3.2Gbps Adaptive Equalizer and Cable Driver MAX3800
Package Information
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3.2Gbps Adaptive Equalizer and Cable Driver
Package Information (continued)
MAX3800
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3.2Gbps Adaptive Equalizer and Cable Driver MAX3800
Package Information (continued)
32L,TQFP.EPS 12 ______________________________________________________________________________________
3.2Gbps Adaptive Equalizer and Cable Driver
Package Information (continued)
MAX3800
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13 (c) 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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