3.2gbps adaptive equalizer and cable driver · 30db cable loss (note 8) 112 200 muip-p output edge...

General DescriptionThe MAX3800 is a +3.3V adaptive cable equalizer andcable driver implemented together on a single chip. It isdesigned for coaxial and twin-axial cable point-to-pointcommunications applications. The driver features differ-ential current-mode logic (CML) inputs and outputs aswell as adjustable output amplitude. The equalizerincludes differential CML data inputs and outputs, aloss-of-signal (LOS) output, and a cable integrity moni-tor (CIM) output.

The adaptive cable equalizer is capable of equalizingdifferential or single-ended signals at data rates up to3.2Gbps. It automatically adjusts to attenuation causedby skin-effect losses of up to 30dB at 1.6GHz. Theequalizer effectively extends the usable length of cop-per cable in high-frequency interconnect applications.

The MAX3800 is available in a 32-pin TQFP packagewith exposed pad and consumes only 200mW at+3.3V. The driver can be disconnected from the powersupply when it is not needed, resulting in a 40% reduc-tion in supply current.

ApplicationsHigh-Speed Links in Communicationsand Data Systems

Backplane and Interconnect Applications

SDH/SONET Transmission Equipment

Features♦ Single +3.3V Operation

♦ Typical Power Dissipation = 200mW at +3.3V

♦ Data Rates Up to 3.2Gbps

♦ Adjustable Cable Driver Output Amplitude

♦ Equalizer Automatically Adjusts for DifferentCable 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 Cable Inputs and Outputs

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3.2Gbps Adaptive Equalizer and Cable Driver

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

DOUT

EIN

DIN

EOUT

MAX3800

DOUT

EIN

DIN

THIS SYMBOL INDICATES A CONTROLLED-IMPEDANCE TRANSMISSION LINE.

EOUT

RMOD CIM

MAX3800

CARD

2

CARD

1

+3.3V +3.3V

LOS RMOD CIMLOS

Typical Application Circuit

19-1953; Rev 3; 12/05

PARTTEMP

RANGE

PIN-PACKAGE

PKGCODE

MAX3800UGJ 0°C to +85°C 32 QFN G3255-1

MAX3800UHJ 0°C to +85°C 32 TQFP-EP* AA-EP

MAX3800UHJ+ 0°C to +85°C 32 TQFP-EP* AA-EP

*EP = exposed pad+Denotes lead-free package.

Pin Configuration appears at end of data sheet.

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.

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2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

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.)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functionaloperation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure toabsolute maximum rating conditions for extended periods may affect device reliability.

Supply Voltage, VCC..............................................-0.5V to +6.0VVoltage 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- ................25mAContinuous Power Dissipation (TA = +85°C)

32-Pin TQFP-EP (derate 22.2mW/°C above +85°C) ...1444mW

Operating Ambient Temperature Range ................0°C to +85°CStorage Temperature Range .............................-55°C to +150°CLead Temperature (soldering, 10s) .................................+300°C

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Supply Current ICC Includes external load current (Note 1) 65 85 mA

CABLE DRIVER INPUT SPECIFICATIONS

Input Voltage (Single-Ended)VDIN+,VDIN-

VCC- 0.6

VCC+ 0.2

V

Input Voltage (Differential) VDIN VDIN = (VDIN+) - (VDIN-) 400 1100 mVp-p

Input Impedance Single-ended 45 55 65 ΩCABLE DRIVER OUTPUT SPECIFICATIONS

RMOD = 10kΩ (Note 2) 750 870 1000 mVp-pOutput Voltage(Differential) RMOD = 20kΩ (Note 2) 400 450 550 mVp-p

Output Impedance Single-ended 50 62.5 75 ΩCABLE EQUALIZER INPUT SPECIFICATIONS

M i ni m um C ab l e Inp ut ( D i ffer enti al ) 3.2Gbps, 30dB cable loss at 1.6GHz (Note 3) 650 700 mVp-p

M axi m um C ab l e Inp ut ( D i ffer enti al ) 1100 mVp-p

Input Impedance Single-ended 45 55 65 ΩCABLE EQUALIZER OUTPUT SPECIFICATIONS

Output Voltage (Differential) (Note 2) 500 1000 mVp-p

Output Impedance Single-ended 50 62.5 75 ΩV ol tag e at C IM Outp ut ( D i ffer enti al ) VCIM No external load, VCIM = (VCIM+) - (VCIM-) -0.5 +0.5 Vp-p

Voltage at CIM Output(Single-Ended)

VCIM+,VCIM-

No external load 0.5VCC- 0.5

V

Output high (Note 4) 2.4 VVoltage at LOS

Output low (Note 4) 0.4 V

Outp ut C om m on- M od e V ol tag e Each output DC-coupled 50Ω to VCC VCC - 0.2 V

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Note 1: Equalizer and driver total currents (equalizer with maximum equalization and driver with maximum output swing).Note 2: Input voltage within specification limits, 50Ω to VCC at each output.Note 3: Minimum cable input for LOS to assert high.Note 4: 100kΩ load to ground.Note 5: AC electrical characteristics are guaranteed by design and characterization.Note 6: VDIN = 400mVp-p to 1100mVp-p (differential), 10kΩ ≤ RMOD ≤ 20kΩ, 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.

AC 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.) (Note 5)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Maximum Input Data Rate 3.2 Gbps

CABLE DRIVER SPECIFICATIONS

Random Jitter (Note 6) 2 4 mUIRMS

Deterministic Jitter (Note 6) 20 60 mUIp-p

Output Edge Speed 20% to 80% 59 76 ps

Input Return Loss (Single-Ended) ≤3.2GHz 14 dB

Outp ut Retur n Loss ( S i ng l e- E nd ed ) ≤3.2GHz 14 dB

EQUALIZER SPECIFICATIONS

0dB cable loss (Note 8) 170 240 mUIp-p

24dB cable loss (Note 8) 97 200 mUIp-pResidual Jitter (Note 7)

30dB cable loss (Note 8) 112 200 mUIp-p

Output Edge Speed 20% to 80% 56 77 ps

Input Return Loss (Single-Ended) ≤3.2GHz 14 dB

Outp ut Retur n Loss ( S i ng l e- E nd ed ) ≤3.2GHz 14 dB

Equalization Compensation 1.6GHz (skin-effect losses only) 30 dB

Equalization Time Constant 5 µs

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4 _______________________________________________________________________________________

20

30

25

40

35

50

45

55

65

60

70

0 20 30 4010 50 60 70 80 90

SUPPLY CURRENT vs. TEMPERATURE

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1

TEMPERATURE (°C)

SUPP

LY C

URRE

NT (m

A)

DRIVER + EQUALIZER

EQUALIZER

DRIVER

400

600

500

900

800

700

1200

1100

1000

1300

4 107 13 16 19 22

CABLE DRIVER OUTPUT VOLTAGE vs. RMOD

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2

RMOD (kΩ)

DRIV

ER O

UTPU

T VO

LTAG

E (m

V)

-50

-30

-40

-10

-20

10

0

20

40

30

50

0 0.8 1.2 1.60.4 2.0 2.4 2.8 3.63.2 4.0

DRIVER INPUT RETURN LOSS (S11)

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3

FREQUENCY (GHz)

GAIN

(dB)

-50

-30

-40

-10

-20

10

0

20

40

30

50

0 0.8 1.2 1.60.4 2.0 2.4 2.8 3.63.2 4.0

DRIVER OUTPUT RETURN LOSS (S22)

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4

FREQUENCY (GHz)

GAIN

(dB)

30

35

45

40

50

55

0.001 0.10.01 1 10 100

EQUALIZER RESIDUAL JITTER vs. POWER SUPPLYNOISE (100mVp-p SINE WAVE) (40FT OF MADISON#14887 SHIELDED TWISTED PAIR-DIFFERENTIAL)

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5

NOISE FREQUENCY (MHz)

JITTE

R (p

s p-p

)

40

60

50

80

70

100

90

110

40 50 5545 60 65 70 75 80 85 (INCHES)

EQUALIZER RESIDUAL JITTER vs. LINE LENGTH(FR-4 6MIL STRIPLINE - SINGLE-ENDED)

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LINE LENGTH

JITTE

R (p

s p-p

)

3.2Gbps622Mbps

2.5Gbps

1.02 1.27 1.401.14 1.52 1.65 1.77 1.90 2.03 2.16 (METERS)

20

30

40

50

60

70

80

90

100

10 20 30 40 50 (FEET)

EQUALIZER RESIDUAL JITTER vs.CABLE LENGTH (MADISON #13887 SHIELDED

TWISTED PAIR-DIFFERENTIAL)

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7

CABLE LENGTH

JITTE

R (p

s p-p

)

3.2Gbps622Mbps2.5Gbps

3.05 6.1 9.14 12.19 15.24 (METERS)

40

80

60

120

100

140

160

25 55 6535 45 75 85 95 (FEET)

EQUALIZER RESIDUAL JITTER vs.CABLE LENGTH (RG179B 75Ω COAXIAL

CABLE - SINGLE-ENDED)

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CABLE LENGTH

JITTE

R (p

s p-p

) 3.2Gbps

622Mbps

2.5Gbps

7.65 16.76 19.8110.67 13.72 22.86 25.91 28.96 (METERS)

70

80

100

90

120

130

110

140

300 500 600400 700 800 900 1000 1100

EQUALIZER RESIDUAL JITTER vs. CABLEINPUT AMPLITUDE (RG179B 75ΩCOAXIAL CABLE - SINGLE-ENDED)

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CABLE INPUT AMPLITUDE (mV)

JITTE

R (p

s p-p

)25 FT

72 FT

Typical Operating Characteristics(TA = +25°C, VCC = +3.3V, all jitter measurements done at 3.2Gbps, 700mV cable input with 213-1 PRBS pattern with 100 consecutiveones and 100 consecutive zeros substituted. Note: Test pattern produces near worst-case jitter results. Results will vary with pattern,unless otherwise noted.)

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_______________________________________________________________________________________ 5

EQUALIZER INPUT AFTER 115FT OF CABLE (TOP)

EQUALIZER OUTPUT (BOTTOM)M

AX38

00 to

c10

EQUALIZER OUTPUT EYE DIAGRAMAFTER 115FT OF 50Ω GORE 89 CABLE

(DIFFERENTIAL, 27-1 PRBS)

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60ps/div (2.5Gbps)

EQUALIZER OUTPUT EYE DIAGRAMAFTER 100FT OF 75Ω RG179 CABLE

(SINGLE-ENDED, 27-1 PRBS)

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68ps/div (2.5Gbps)

EQUALIZER OUTPUT EYE DIAGRAMAFTER 100FT OF BELDEN 9207 CABLE

(DIFFERENTIAL, 27-1 PRBS)

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3

60ps/div (2.5Gbps) 60ps/div (2.5Gbps)

EQUALIZER OUTPUT EYE DIAGRAMAFTER 50FT OF MADISON #14887 SHIELDED TWISTED PAIR CABLE

(DIFFERENTIAL, 27-1 PRBS)M

AX38

00 to

c14

1.2

1.5

1.4

1.3

1.6

1.7

1.8

0 403010 20 50 60 70 80 90 100

CIM VOLTAGE vs. CABLE LENGTH(RG179B 75Ω COAXIAL CABLE -

SINGLE-ENDED)

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CABLE LENGTH (FEET)

CIM

VOL

TAGE

(V)

CIM-

CIM+

-50

-30

-40

-10

-20

10

0

20

40

30

50

0 0.8 1.2 1.60.4 2.0 2.4 2.8 3.63.2 4.0

EQUALIZER INPUT RETURN LOSS (S11)

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6

FREQUENCY (GHz)

GAIN

(dB)

-50

-30

-40

-10

-20

10

0

20

40

30

50

0 0.8 1.2 1.60.4 2.0 2.4 2.8 3.63.2 4.0

EQUALIZER OUTPUT RETURN LOSS (S22)

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7

FREQUENCY (GHz)

GAIN

(dB)

Typical Operating Characteristics (continued)(TA = +25°C, VCC = +3.3V, all jitter measurements done at 3.2Gbps, 700mV cable input with 213-1 PRBS pattern with 100 consecutiveones and 100 consecutive zeros substituted. Note: Test pattern produces near worst-case jitter results. Results will vary with pattern,unless otherwise noted.)

Detailed DescriptionThe MAX3800 consists of a cable driver (transmitter)and an adaptive cable equalizer (receiver). The driverand equalizer are implemented on the same chip, butthey are completely independent.

The Cable DriverThe cable driver accepts differential or single-endedcurrent-mode logic (CML) input data at rates up to3.2Gbps. The driver output is also implemented usingCML. The maximum output amplitude can be adjustedover a typical range of 450mV to 870mV by changingthe value of the RMOD resistor between 10kΩ and20kΩ (this resistor is connected between the RMOD pinand ground).

The Adaptive Cable EqualizerThe adaptive cable equalizer accepts differential CMLinput data at rates up to 3.2Gbps and is capable ofequalizing differential or single-ended signals. It auto-matically adjusts to attenuation levels of up to 30dB at1.6GHz (due to skin-effect losses in copper cable). Theequalizer consists of a CML input buffer, a loss-of-sig-

nal detector, a flat response amplifier, a skin-effectcompensation amplifier, a current-steering network, adual power-detector feedback loop, an output limitingamplifier, and a CML output buffer (Figure 1).

General Theory of OperationThe shape of the power spectrum of a random bitstream can be described by the square of the sincfunction, where sinc f = (sin πf) / πf. For sufficiently longbit patterns (nonrandom bit streams), sinc2(f) is a goodapproximation. From the shape of the sinc2(f) function,we can estimate the ratio of the power densities at anytwo frequencies. The MAX3800 adaptive equalizeremploys this principle by incorporating a feedback loopthat continuously monitors the power at two frequenciesand dynamically adjusts the equalizer to maintain thecorrect power ratio.

CML Input and Output BuffersThe input and output buffers are implemented usingcurrent-mode logic (CML). Equivalent circuits areshown in Figures 2 and 3. For details on interfacing with

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6 _______________________________________________________________________________________

PIN NAME FUNCTION

1, 3, 6, 11, 14 VCCE Equalizer Power Supply

2, 7, 10, 15,23, 24, 26, 31

GND Ground

4 EIN+ Positive Equalizer Input, CML

5 EIN- Negative Equalizer Input, CML

8 CIM- Negative Cable Integrity Monitor (CIM) Output

9 CIM+ Positive Cable Integrity Monitor (CIM) Output

12 EOUT- Negative Equalizer Output, CML

13 EOUT+ Positive Equalizer Output, CML

16, 17 N.C. No Connection. Leave unconnected.

18 LOS Equalizer Loss-of-Signal Output, Active-Low

19, 22, 27,30, 32

VCCD Driver Power Supply

20 DIN+ Positive Driver Input, CML

21 DIN- Negative Driver Input, CML

25 RMODDriver Output Modulation Adjust. A resistor connected from this pin to GND controls driver outputvoltage.

28 DOUT+ Positive Driver Output, CML

29 DOUT- Negative Driver Output, CML

EPExposed

PadGround. The exposed pad must be soldered to the circuit board ground plane for proper thermaland electrical performance.

Pin Description

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_______________________________________________________________________________________ 7

VARIABLEATTENUATOR

LIMITINGAMP

CABLEDRIVER

FLATRESPONSEAMP

Σf√

MAX3800

LOOPFILTER

|H(f)|

|H(f)|

VARIABLEATTENUATOR

200M

HzPW

R DE

TECT

OR

600M

HzPW

R DE

TECT

OR

CIM

-

CIM

+

CMLCML

CMLCML

RMOD

EIN

DOUT

EOUT

DIN

P0WERDETECTOR

LOS

CURRENT STEERING NETWORK

SKINEFFECTCOMPEN-SATIONAMP

Figure 1. Functional Diagram

IN-

IN+

GND

ESDSTRUCTURES

VCC

50Ω 50Ω

GND

ESDSTRUCTURES

62.5Ω 62.5Ω

OUT-

OUT+

VCC

Figure 2. CML Input Equivalent Circuit Figure 3. CML Output Equivalent Circuit

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Flat Response and Skin-EffectCompensation Amplifiers

The buffered input waveform is fed equally to twoamplifiers—the flat response amplifier and the skin-effect compensation amplifier. The flat response ampli-fier has a constant gain over the entire frequency rangeof the device, and the skin-effect compensation amplifi-er has a gain characteristic that approximates theinverse of the skin-effect attenuation inherent in coppercable. The skin-effect attenuation, in dB per unit length,is proportional to the square root of the frequency. Theoutput currents from the two amplifiers are supplied tothe current-steering network. Note that when LOSasserts low, equalization is minimized.

Current-Steering NetworkThe function of the current-steering network is to com-bine adjustable quantities of the output currents fromthe flat response and skin-effect compensation ampli-fiers to achieve a desired current ratio. The ratio adjust-ment is controlled by the dual power-detector feedbackloop.

The current-steering network is implemented with a pairof variable attenuators that feed into a current-summingnode. The variable attenuators are used to attenuatethe output currents of the flat response and skin-effectcompensation amplifiers under control of the dualpower-detector feedback loop. The outputs of the twoattenuators are combined at the summing node andthen fed to the output limiting amplifier and the feed-back loop.

Dual Power-Detector Feedback LoopThe output of the current-steering network is applied tothe inputs of two frequency-specific power detectors.One of the power detectors is tuned to 200MHz and theother is tuned to 600MHz. The outputs of the two powerdetectors are applied to the inverting (200MHz powerdetector) and noninverting (600MHz power detector)inputs of the differential loop amplifier. The differentialoutputs of the loop amplifier control the variable attenu-ators in the current-steering network.

Output Limiting AmplifierThe output limiting amplifier amplifies the signal fromthe current-steering network to achieve the specifiedoutput voltage swing.

Applications InformationRefer to Maxim application note HFDN-10.0, EqualizingGigabit Copper Cable Links with the MAX3800 (avail-able at www.maxim-ic.com) for additional applicationsinformation.

Selecting RMODThe cable driver output amplitude can be adjusted byconnecting a resistor with a value from 10kΩ to 20kΩbetween the RMOD pin and ground. The exact outputamplitude of the driver for a given value of RMOD resis-tance is dependent on a number of factors. Refer to theTypical Operating Characteristics “Cable Driver OutputVoltage vs. RMOD” for typical values.

Cable Integrity Monitor (CIM)The differential CIM output current is directly propor-tional to the output current of the loop amplifier (whichcontrols the current-steering network—see DetailedDescription). This is an analog current output that indi-cates the amount of equalization that is being applied.A convenient way to monitor the CIM current is to con-nect a 100kΩ resistor from each of the CIM outputs toground, and then measure the voltage at the CIM pins.

The amount of equalization (and thus the CIM outputlevel) is affected by various factors, including cabletype, cable length, signal bandwidth, etc. Refer to theTypical Operating Characteristics “CIM Voltage vs.Cable Length” for typical values under specific condi-tions.

Loss-of-Signal (LLOOSS) OutputLoss-of-signal is indicated by the LOS output. A lowlevel on LOS indicates that the equalizer input signalpower has dropped below a threshold. The LOS outputindicates a loss of signal. When the equalizer no longerdetects a signal from the channel, the LOS output goeslow. When there is sufficient input voltage to the chan-nel (typically greater that 650mV), LOS is high. The LOSoutput is suitable for indicating problems with the trans-mission link caused by, for example, a broken cable, adefective driver, or a lost connection to the equalizer.


8 _______________________________________________________________________________________

Single-Ended OperationFor single-ended operation of the cable driver or equal-izer, connect the unused input to ground through aseries combination of a capacitor (of equal value toother AC-coupling capacitors) and a 50Ω resistor. Notethat the MAX3800 is specified for differential operation.

Layout ConsiderationsThe MAX3800’s performance can be significantlyaffected by circuit-board layout and design. Use goodhigh-frequency design techniques, including minimiz-ing ground inductance and using fixed-impedancetransmission lines for the high-frequency data signals.Power-supply decoupling capacitors should be placedas close as possible to VCC.

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MAX3800

TOP VIEW

32 28293031 252627

GND

V CCD

DOUT

-

DOUT

+

V CCD

V CCD

GND

RMOD

10 13 1514 1611 129

CIM

+

V CCE

GND

EOUT

+

EOUT

-

GND

V CCE

N.C.

2

3

4

5

6

7

8CIM-

GND

VCCE

EIN-

EIN+

VCCE

GND

1VCCE

17

18

19

20

21

22

23 GND

24 GND

VCCD

DIN-

DIN+

VCCD

N.C.

LOS

Pin Configuration

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10 ______________________________________________________________________________________

32L

QFN

.EP

S

Package Information(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline informationgo to www.maxim-ic.com/packages.)

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______________________________________________________________________________________ 11

Package Information (continued)(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline informationgo to www.maxim-ic.com/packages.)

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12 ______________________________________________________________________________________

32L,

TQFP

.EP

S

F1

221-0079

PACKAGE OUTLINE,32L TQFP, 5x5x1.0mm, EP OPTION


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Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses areimplied. 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

© 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.

F2

221-0079

PACKAGE OUTLINE,32L TQFP, 5x5x1.0mm, EP OPTION


3.2gbps adaptive equalizer and cable driver · 30db cable loss (note 8) 112 200 muip-p output edge...

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