19-1953; Rev 1; 11/01 3.2Gbps Adaptive Equalizer and Cable Driver 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. 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 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 Cable Inputs and Outputs Applications Ordering Information High-Speed Links in Communications and Data Systems MAX3800UGJ 0°C to +85°C 32 QFN Backplane and Interconnect Applications MAX3800UHJ 0°C to +85°C 32 TQFP-EP* SDH/SONET Transmission Equipment PART TEMP. RANGE PIN-PACKAGE *EP = exposed pad Pin Configuration appears at end of data sheet. Typical Application Circuit +3.3V CARD 1 DIN DOUT MAX3800 EOUT LOS RMOD EOUT EIN CARD 2 +3.3V MAX3800 EIN DOUT CIM LOS DIN RMOD 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 MAX3800 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. MAX3800 3.2Gbps Adaptive Equalizer and Cable Driver 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 = +85°C) 32-Pin TQFP-EP (derate 22.2mW/°C above +85°C) ...1444mW 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 CONDITIONS ICC MIN Includes external load current (Note 1) TYP MAX UNITS 65 85 mA VCC + 0.2 V CABLE DRIVER INPUT SPECIFICATIONS Input Voltage (Single-Ended) Input Voltage (Differential) VCC - 0.6 VDIN+, VDINVDIN VDIN = (VDIN+) - (VDIN-) 400 1100 mVp-p Single-ended 45 55 65 Ω Output Voltage (Differential) RMOD = 10kΩ (Note 2) 750 870 1000 mVp-p RMOD = 20kΩ (Note 2) 400 450 550 mVp-p Output Impedance Single-ended 50 62.5 75 Ω 650 700 mVp-p Input Impedance CABLE DRIVER OUTPUT SPECIFICATIONS CABLE EQUALIZER INPUT SPECIFICATIONS Minimum Cable Input (Differential) 3.2Gbps, 30dB cable loss at 1.6GHz (Note 3) Maximum Cable Input (Differential) 1100 Input Impedance Single-ended 45 55 mVp-p 65 Ω 1000 mVp-p CABLE EQUALIZER OUTPUT SPECIFICATIONS Output Voltage (Differential) (Note 2) 500 Output Impedance Single-ended 50 Voltage at CIM Output (Differential) Voltage at CIM Output (Single-Ended) Voltage at LOS Output Common-Mode Voltage 2 VCIM VCIM+, VCIM- 62.5 75 Ω No external load, VCIM = (VCIM+) - (VCIM-) -0.5 +0.5 Vp-p No external load 0.5 VCC - 0.5 V Output high (Note 4) 2.4 V Output low (Note 4) Each output DC-coupled 50Ω to VCC 0.4 VCC - 0.2 _______________________________________________________________________________________ V V 3.2Gbps Adaptive Equalizer and Cable Driver (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 Maximum Input Data Rate MIN TYP MAX 3.2 UNITS 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 Output Return Loss (Single-Ended) ≤3.2GHz 14 dB 0dB cable loss (Note 8) 170 240 mUIp-p 24dB cable loss (Note 8) 97 200 mUIp-p mUIp-p EQUALIZER SPECIFICATIONS Residual Jitter (Note 7) 30dB cable loss (Note 8) 112 200 Output Edge Speed 20% to 80% 56 77 Input Return Loss (Single-Ended) ≤3.2GHz 14 dB Output Return Loss (Single-Ended) ≤3.2GHz 14 dB Equalization Compensation 1.6GHz (skin-effect losses only) Equalization Time Constant 30 ps dB 5 µs Equalizer and driver total currents (equalizer with maximum equalization and driver with maximum output swing). Input voltage within specification limits, 50Ω to VCC at each output. Minimum cable input for LOS to assert high. 100kΩ load to ground. AC electrical characteristics are guaranteed by design and characterization. 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. Note 1: Note 2: Note 3: Note 4: Note 5: Note 6: _______________________________________________________________________________________ 3 MAX3800 AC ELECTRICAL CHARACTERISTICS 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 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 50 45 EQUALIZER 30 20 1000 900 800 0 -10 -20 600 -30 25 500 -40 20 400 30 DRIVER 0 10 20 30 40 50 60 70 80 90 -50 4 7 10 13 16 19 0 22 RMOD (kΩ) FREQUENCY (GHz) DRIVER OUTPUT RETURN LOSS (S22) EQUALIZER RESIDUAL JITTER vs. POWER SUPPLY NOISE (100mVp-p SINE WAVE) (40FT OF MADISON #14887 SHIELDED TWISTED PAIR-DIFFERENTIAL) EQUALIZER RESIDUAL JITTER vs. CABLE INPUT AMPLITUDE (RG179B 75Ω COAXIAL CABLE - SINGLE-ENDED) MAX3800 toc04 40 30 55 140 50 130 25 FT 120 10 0 -10 JITTER (psp-p) JITTER (psp-p) 20 45 40 110 100 72 FT -20 90 -30 35 80 -40 -50 30 0.001 70 FREQUENCY (GHz) NOISE FREQUENCY (MHz) 300 400 500 600 700 800 900 1000 1100 CABLE INPUT AMPLITUDE (mV) EQUALIZER RESIDUAL JITTER vs. CABLE LENGTH (MADISON #13887 SHIELDED TWISTED PAIR-DIFFERENTIAL) EQUALIZER RESIDUAL JITTER vs. CABLE LENGTH (RG179B 75Ω COAXIAL CABLE - SINGLE-ENDED) EQUALIZER RESIDUAL JITTER vs. LINE LENGTH (FR-4 6MIL STRIPLINE - SINGLE-ENDED) 90 0.1 1 160 MAX3800 toc07 100 0.01 2.5Gbps 140 10 100 110 100 80 2.5Gbps 50 3.2Gbps 622Mbps 120 JITTER (psp-p) 60 JITTER (psp-p) 90 70 3.2Gbps 100 80 60 30 20 6.1 30 40 9.14 12.19 CABLE LENGTH 50 (FEET) 15.24 (METERS) 40 70 622Mbps 2.5Gbps 3.2Gbps 50 622Mbps 10 3.05 80 60 40 20 MAX3800 toc09 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0 MAX3800 toc08 0 4 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0 TEMPERATURE (°C) 50 GAIN (dB) 10 700 35 MAX3800 toc03 MAX3800 toc02 1100 40 MAX3800 toc06 40 1200 GAIN (dB) 55 50 MAX3800 toc05 SUPPLY CURRENT (mA) 60 1300 DRIVER OUTPUT VOLTAGE (mV) DRIVER + EQUALIZER 65 DRIVER INPUT RETURN LOSS (S11) CABLE DRIVER OUTPUT VOLTAGE vs. RMOD MAX3800 toc01 70 JITTER (psp-p) MAX3800 3.2Gbps Adaptive Equalizer and Cable Driver 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 _______________________________________________________________________________________ 3.2Gbps Adaptive Equalizer and Cable Driver EQUALIZER OUTPUT EYE DIAGRAM AFTER 100FT OF 75Ω RG179 CABLE (SINGLE-ENDED, 27-1 PRBS) EQUALIZER OUTPUT EYE DIAGRAM AFTER 115FT OF 50Ω GORE 89 CABLE (DIFFERENTIAL, 27-1 PRBS) MAX3800 toc12 MAX3800 toc11 MAX3800 toc10 68ps/div (2.5Gbps) 60ps/div (2.5Gbps) EQUALIZER OUTPUT EYE DIAGRAM AFTER 50FT OF MADISON #14887 SHIELDED TWISTED PAIR CABLE (DIFFERENTIAL, 27-1 PRBS) CIM VOLTAGE vs. CABLE LENGTH (RG179B 75Ω COAXIAL CABLE SINGLE-ENDED) 1.8 MAX3800 toc14 MAX3800 toc13 EQUALIZER OUTPUT EYE DIAGRAM AFTER 100FT OF BELDEN 9207 CABLE (DIFFERENTIAL, 27-1 PRBS) CIM- 1.7 CIM VOLTAGE (V) MAX3800 toc15 EQUALIZER INPUT AFTER 115FT OF CABLE (TOP) EQUALIZER OUTPUT (BOTTOM) 1.6 1.5 1.4 1.3 CIM+ 1.2 60ps/div (2.5Gbps) 60ps/div (2.5Gbps) 0 10 20 30 40 50 60 70 80 90 100 CABLE LENGTH (FEET) EQUALIZER OUTPUT RETURN LOSS (S22) EQUALIZER INPUT RETURN LOSS (S11) 30 40 30 20 10 10 GAIN (dB) 20 0 -10 MAX3800 toc17 40 GAIN (dB) 50 MAX3800 toc16 50 0 -10 -20 -20 -30 -30 -40 -40 -50 -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 MAX3800 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 consecutive ones and 100 consecutive zeros substituted. Note: Test pattern produces near worst-case jitter results. Results will vary with pattern, unless otherwise noted.) 3.2Gbps Adaptive Equalizer and Cable Driver MAX3800 Pin Description PIN NAME 1, 3, 6, 11, 14 VCCE Equalizer Power Supply FUNCTION 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+ 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- Positive Equalizer Output, CML Negative Driver Input, CML Driver Output Modulation Adjust. A resistor connected from this pin to GND controls driver output voltage. 25 RMOD 28 DOUT+ Positive Driver Output, CML 29 DOUT- Negative Driver Output, CML EP Exposed Pad Ground. The exposed pad must be soldered to the circuit board ground plane for proper thermal and electrical performance. 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. 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 10kΩ and 20kΩ (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 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 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 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 _______________________________________________________________________________________ CIM- MAX3800 CIM+ 3.2Gbps Adaptive Equalizer and Cable Driver 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 CML EOUT VARIABLE ATTENUATOR CURRENT STEERING NETWORK MAX3800 LOS DOUT LIMITING AMP CABLE DRIVER CML DIN CML RMOD Figure 1. Functional Diagram VCC VCC ESD STRUCTURES 62.5Ω 50Ω 62.5Ω 50Ω OUT+ IN+ OUT- IN- ESD STRUCTURES GND GND Figure 2. CML Input Equivalent Circuit Figure 3. CML Output Equivalent Circuit _______________________________________________________________________________________ 7 MAX3800 3.2Gbps Adaptive Equalizer and Cable Driver 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. 8 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 10kΩ to 20kΩ 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 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. Refer to the Typical Operating Characteristics “CIM Voltage vs. Cable Length” for typical values under specific conditions. 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. _______________________________________________________________________________________ 3.2Gbps Adaptive Equalizer and Cable Driver MAX3800 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 50Ω resistor. Note that the MAX3800 is specified for differential operation. 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 VCCD GND VCCD DOUT- DOUT+ VCCD GND RMOD TOP VIEW 32 31 30 29 28 27 26 25 VCCE 1 24 GND GND 2 23 GND VCCE 3 22 VCCD EIN+ 4 21 DIN- MAX3800 EIN- 5 VCCE 6 19 VCCD GND 7 18 LOS CIM- 8 17 N.C. 10 11 12 13 14 15 16 GND VCCE EOUT- EOUT+ VCCE GND N.C. CIM+ 9 20 DIN+ _______________________________________________________________________________________ 9 3.2Gbps Adaptive Equalizer and Cable Driver MAX3800 Package Information 10 ______________________________________________________________________________________ 3.2Gbps Adaptive Equalizer and Cable Driver ______________________________________________________________________________________ 11 MAX3800 Package Information (continued) 3.2Gbps Adaptive Equalizer and Cable Driver 32L,TQFP.EPS MAX3800 Package Information (continued) 12 ______________________________________________________________________________________ 3.2Gbps Adaptive Equalizer and Cable Driver 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 © 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX3800 Package Information (continued)