19-4695; Rev 1; 6/10 KIT ATION EVALU E L B AVAILA 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver The MAX3799 is a highly integrated limiting amplifier and VCSEL driver that operates up to 14Gbps, making it suitable for Ethernet and Fibre Channel applications. By providing a selectable data path with a noise-shaping filter, the MAX3799 enables a module with 10G optics to be fully compliant with both 1000BASE-SR and 10GBASE-SR specifications. 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 amplifier 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 backterminated for a 50 transmission line PCB design. The use of a 3-wire digital interface reduces the pin count while enabling advanced Rx (rate selection, LOS threshold, LOS squelch, LOS polarity, CML output level, signal path polarity, deemphasis, and fast mode-select change time) and Tx settings (modulation current, bias current, polarity, and eye safety control) without the need for external components. The MAX3799 provides multiple current and voltage DACs to allow the use of low-cost controller ICs. The MAX3799 is packaged in a lead-free, 5mm x 5mm, 32-pin TQFN package. Applications Features Enables Single-Module Design Compliance with 1000BASE-SR and 10GBASE-SR Specifications -21.5dBm Optical Sensitivity at 1.25Gbps Using a 10.32Gbps ROSA (-19.7dBm OMA) Low Power Dissipation of 320mW at 3.3V Power Supply Typical Electrical Performance of 14.025Gbps on Rx/Tx (Non-Retimed 16x Fibre Channel Solution) 3mVP-P Receiver Sensitivity at 10.32Gbps 4psP-P DJ at Receiver Output at 8.5Gbps 8B/10B 4psP-P DJ at Receiver Output at 10.32Gbps 231 - 1 PRBS 26ps Rise and Fall Time at Rx/Tx Output Rate Select for 1Gbps Mode or 10Gbps Mode CML Output Squelch Polarity Select for Rx and Tx LOS Assert Level Adjustment LOS Polarity Select Modulation Current Up to 12mA Into 100 Differential Load Bias Current Up to 15mA Integrated Eye Safety Features 3-Wire Digital Interface Programmable Deemphasis at Tx Output 1000BASE-SR/10GBASE-SR Multirate SFP+ Optical Transceiver 1x/2x/4x/8x/16x SFF/SFP/SFP+ MSA Fibre Channel (FC) Optical Transceiver Ordering Information PART TEMP RANGE PIN-PACKAGE MAX3799ETJ+ -40C to +85C 32 TQFN-EP* MAX3799E/D -40C to +85C Dice** +Denotes a lead(Pb)-free/RoHS-compliant package. *EP = Exposed pad. **Tested at TA = +25C. Typical Application Circuit and Pin Configuration appear at end of data sheet. ________________________________________________________________ Maxim Integrated Products 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 MAX3799 General Description MAX3799 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver ABSOLUTE MAXIMUM RATINGS VCCR, VCCT, VCCD.................................................-0.3V to +4.0V Voltage Range at DISABLE, SDA, SCL, CSEL, RSEL, FAULT, BMON, LOS, CAZ2.........-0.3V to (VCC + 0.3V) Voltage Range at ROUT+, ROUT- .....(VCC - 1V) to (VCC + 0.3V) Voltage at TIN+, TIN-........................(VCC - 2.5V) to (VCC - 0.5V) Voltage Range at TOUT+, TOUT- ......(VCC - 2V) to (VCC + 0.3V) Voltage at BIAS ............................................................0V to VCC Voltage at RIN+, RIN- ..........................(VCC - 2V) to (VCC - 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 (TA = +70C) 32-Pin TQFN (derate 34.5W/C above +70C) ...........2759mW Operating Junction Temperature Range ...........-55C to +150C Storage Temperature Range .............................-65C to +160C Lead Temperature (soldering, 10s) .................................+300C Soldering Temperature (reflow) .......................................+260C 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 (VCC = 2.85V to 3.63V, TA = -40C to +85C, CML receiver output load is AC-coupled to differential 100, CAZ = 1nF, transmitter output load is AC-coupled to differential 100 (see Figure 1), typical values are at +25C, VCC = 3.3V, IBIAS = 6mA, IMOD = 6mA, unless otherwise specified. Registers are set to default values unless otherwise noted, and the 3-wire interface is static during measurements. For testing, the RATE_SEL bit was used and the RSEL pin was left open.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 97 150 mA 2.85 3.63 V 1.0625 10.32 Gbps POWER SUPPLY Power-Supply Current ICC Power-Supply Voltage VCC Includes the CML output current; excludes IBIAS = 6mA, IMOD = 6mA, VDIFF_ROUT = 400mV P-P (Note 1) GENERAL Input Data Rate Input/Output SNR 14.1 BER 10E-12 POWER-ON RESET High POR Threshold 2.55 Low POR Threshold IBIAS = IBIASOFF and IMOD = IMODOFF 2.75 2.3 2.45 75 100 125 RATE_SEL = 0 (1.25Gbps) 1 3 RATE_SEL = 1 (10.32Gbps) 3 8 V V Rx INPUT SPECIFICATIONS Differential Input Resistance RIN+/RIN- RIN_DIFF Input Sensitivity (Note 2) VINMIN Input Overload VINMAX Input Return Loss SDD11 Input Return Loss SCC11 1.2 mVP-P VP-P DUT is powered on, f 5GHz 14 DUT is powered on, f 16GHz 7 DUT is powered on, 1GHz < f 5GHz 8 DUT is powered on, 1GHz < f 16GHz 8 dB dB Rx OUTPUT SPECIFICATIONS Differential Output Resistance 2 R OUTDIFF 75 100 _______________________________________________________________________________________ 125 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver (VCC = 2.85V to 3.63V, TA = -40C to +85C, CML receiver output load is AC-coupled to differential 100, CAZ = 1nF, transmitter output load is AC-coupled to differential 100 (see Figure 1), typical values are at +25C, VCC = 3.3V, IBIAS = 6mA, IMOD = 6mA, unless otherwise specified. Registers are set to default values unless otherwise noted, and the 3-wire interface is static during measurements. For testing, the RATE_SEL bit was used and the RSEL pin was left open.) PARAMETER SYMBOL Output Return Loss SDD22 Output Return Loss SCC22 CONDITIONS MIN TYP DUT is powered on, f 5GHz 11 DUT is powered on, f 16GHz 5 DUT is powered on, 1GHz < f 5GHz 9 DUT is powered on, 1GHz < f 16GHz 7 MAX UNITS dB dB CML Differential Output Voltage High 5mVP-P VIN 1200mVP-P, SET_CML[162] 595 800 1005 mVP-P CML Differential Output Voltage Medium 10mV P-P VIN 1200mV P-P, SET_CML[80] 300 400 515 mVP-P CML Differential Output DAC Limit SET_CML[7:0] Differential Output Signal When Disabled Outputs AC-coupled, VINMAX applied to input VDIFF_ROUT = 800mV P-P at 8.5Gbps (Notes 2, 3) 6 15 10mV P-P VIN 1200mV P-P, RATE_SEL = 1, VDIFF_ROUT = 400mVP-P 26 35 5mVP-P VIN 1200mVP-P, RATE_SEL = 0, VDIFF_ROUT = 800mVP-P 60 100 60mV P-P VIN 400mVP-P at 10.32Gbps, RATE_SEL = 1, VDIFF_ROUT = 400mVP-P 4 12 10mV P-P VIN 1200mV P-P at 8.5Gbps, RATE _SEL = 1, VDIFF_ROUT = 400mVP-P 4 12 5mVP-P VIN 1200mVP-P at 1.25Gbps, RATE _SEL = 0, VDIFF_ROUT = 800mVP-P 20 Input = 60mV P-P at 1.25Gbps, RATE_SEL = 0, VDIFF_ROUT = 800mVP-P 1.8 2.5 Input = 60mV P-P at 8.5Gbps, RATE _SEL = 1, VDIFF_ROUT = 400mVP-P 0.32 0.48 Data Output Transition Time (20% to 80%) (Notes 2, 3, 4) tR/tF 215 mVP-P ps Rx TRANSFER CHARACTERISTICS Deterministic Jitter (Notes 2, 3, 5) DJ Random Jitter (Notes 2, 3) Low-Frequency Cutoff RJ psP-P psRMS CAZ = 0.1F 2 CAZ = open 500 kHz Rx LOS SPECIFICATIONS LOS Assert Sensitivity Range 14 LOS Hysteresis 10 x log(VDEASSERT/VASSERT) (Note 6) 1.25 LOS Assert/Deassert Time (Note 7) 2.3 Low Assert Level SET_LOS[7] (Notes 2, 6) 8 Low Deassert Level SET_LOS[7] (Notes 2, 6) 14 Medium Assert Level SET_LOS[32] (Notes 2, 6) 39 77 2.1 mVP-P dB 80 s 11 14 mVP-P 18 21 mVP-P 48 58 mVP-P Medium Deassert Level SET_LOS[32] (Notes 2, 6) 65 81 95 mVP-P High Assert Level SET_LOS[63] (Notes 2, 6) 77 94 112 mVP-P High Deassert Level SET_LOS[63] (Notes 2, 6) 127 158 182 mVP-P _______________________________________________________________________________________ 3 MAX3799 ELECTRICAL CHARACTERISTICS (continued) MAX3799 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver ELECTRICAL CHARACTERISTICS (continued) (VCC = 2.85V to 3.63V, TA = -40C to +85C, CML receiver output load is AC-coupled to differential 100, CAZ = 1nF, transmitter output load is AC-coupled to differential 100 (see Figure 1), typical values are at +25C, VCC = 3.3V, IBIAS = 6mA, IMOD = 6mA, unless otherwise specified. Registers are set to default values unless otherwise noted, and the 3-wire interface is static during measurements. For testing, the RATE_SEL bit was used and the RSEL pin was left open.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Tx INPUT SPECIFICATIONS Differential Input Voltage VIN Common-Mode Input Voltage VINCM Differential Input Resistance RIN Input Return Loss SDD11 Input Return Loss SCC11 Data rate = 1.0625Gbps 0.2 2.4 Data rate = 10.32Gbps 0.075 0.8 2.75 75 100 DUT is powered on, f 5GHz 15 DUT is powered on, f 16GHz 6 DUT is powered on, 1GHz < f 5GHz 9 DUT is powered on, 1GHz < f 16GHz 5 VP-P V 125 dB dB Tx LASER MODULATOR Maximum Modulation-On Current into 100 Differential Load IMODMAX Outputs AC-coupled, VCCTO 2.95V Minimum Modulation-On Current into 100 Differential Load IMODMIN Outputs AC-coupled 2 mA 2mA IMOD 12mA (Note 8) 4 % ps Modulation Current DAC Stability Modulation Current Rise Time/ Fall Time Deterministic Jitter (Notes 2, 9) tR/tF DJ SDD22 mA 5mA IMOD 10mA, 20% to 80%, SET_TXDE[3:0] = 10 (Notes 2, 4) 26 39 5mA IMOD 12mA, at 10.32Gbps, 250mVP-P VIN 800mV P-P, SET_TXDE[3:0] = 0 6 12 5mA IMOD 12mA, at 10.32Gbps, 250mVP-P VIN 800mV P-P, SET_TXDE[3:0] = 10 6 13 5mA IMOD 12mA, at 8.5Gbps, 250mVP-P VIN 800mV P-P, SET_TXDE[3:0] = 0 6 12 5mA IMOD 12mA, at 8.5Gbps, 250mVP-P VIN 800mV P-P, SET_TXDE[3:0] = 10 6 12 2mA IMOD 12mA, at 4.25Gbps 5 2mA IMOD 12mA, at 1.0625Gbps 5 5mA IMOD 12mA, 250mV P-P VIN 800mVP-P Random Jitter Output Return Loss 12 0.17 DUT is powered on, f 5GHz 12 DUT is powered on, f 16GHz 5 0.5 ps psRMS dB Tx BIAS GENERATOR Maximum Bias-On Current IBIASMAX Current into BIAS pin Minimum Bias-On Current IBIASMIN Current into BIAS pin 4 15 _______________________________________________________________________________________ mA 2 mA 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver (VCC = 2.85V to 3.63V, TA = -40C to +85C, CML receiver output load is AC-coupled to differential 100, CAZ = 1nF, transmitter output load is AC-coupled to differential 100 (see Figure 1), typical values are at +25C, VCC = 3.3V, IBIAS = 6mA, IMOD = 6mA, unless otherwise specified. Registers are set to default values unless otherwise noted, and the 3-wire interface is static during measurements. For testing, the RATE_SEL bit was used and the RSEL pin was left open.) PARAMETER SYMBOL Compliance Voltage at BIAS CONDITIONS MIN TYP 2mA IBIAS 15mA (Notes 2, 10) BIAS Current DAC Stability VBIAS 0.9 BIAS Current Monitor Current Gain External resistor to GND defines the voltage gain IBMON Compliance Voltage at BMON VBMON BIAS Current Monitor Current Gain Stability IBMON 2mA IBIAS 15mA (Note 10) VBMON Average voltage, FAULT warning always occurs for VBMON VCC - 0.55V, FAULT warning never occurs for VBMON VCC 0.65V MAX UNITS 4 % 2.1 V 16 0 mA/A 1.8 V 5 % Tx SAFETY FEATURES Excessive Voltage at BMON Excessive Voltage at BIAS Maximum VCSEL Current in Off State VBIAS I OFF VCC 0.65V VCC 0.6V VCC 0.55V V 0.44 0.48 0.65 V FAULT or DISABLE, VBIAS = VCC 25 A 1 s Average voltage, FAULT always occurs for VBIAS 0.44V, FAULT never occurs for VBIAS 0.65V SFP TIMING REQUIREMENTS DISABLE Assert Time t_ OFF Time from rising edge of DISABLE input signal to IBIAS = IBIASOFF and IMOD = IMODOFF DISABLE Negate Time t_ ON Time from falling edge of DISABLE to IBIAS and IMOD at 90% of steady state when FAULT = 0 before reset 500 s FAULT Reset Time of Power-On Time t_INIT Time from power-on or negation of FAULT using DISABLE 100 ms Time from fault to FAULT on, CFAULT 20pF, RFAULT = 4.7k 10 s FAULT Reset Time t_FAULT Time DISABLE must be held high to reset FAULT DISABLE to Reset 5 s OUTPUT_LEVEL VOLTAGE DAC (SET_CML) Full-Scale Voltage VFS 100 differential resistive load 1200 mVP-P 5 mVP-P INL 5mA ICML_LEVEL 20mA 0.9 LSB Resolution Integral Nonlinearity LOS THRESHOLD VOLTAGE DAC (SET_LOS) Full-Scale Voltage VFS Resolution Integral Nonlinearity INL 11mV P-P VTH_LOS 94mVP-P 94 mVP-P 1.5 mVP-P 0.7 LSB 21 mA BIAS CURRENT DAC (SET_IBIAS) Full-Scale Current IFS _______________________________________________________________________________________ 5 MAX3799 ELECTRICAL CHARACTERISTICS (continued) MAX3799 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver ELECTRICAL CHARACTERISTICS (continued) (VCC = 2.85V to 3.63V, TA = -40C to +85C, CML receiver output load is AC-coupled to differential 100, CAZ = 1nF, transmitter output load is AC-coupled to differential 100 (see Figure 1), typical values are at +25C, VCC = 3.3V, IBIAS = 6mA, IMOD = 6mA, unless otherwise specified. Registers are set to default values unless otherwise noted, and the 3-wire interface is static during measurements. For testing, the RATE_SEL bit was used and the RSEL pin was left open.) PARAMETER SYMBOL CONDITIONS MIN Resolution Integral Nonlinearity Differential Nonlinearity TYP MAX UNITS 40 A INL 1mA IBIAS 15mA 1 LSB DNL 1mA IBIAS 15mA, guaranteed monotonic at 8-bit resolution (SET_IBIAS[8:1]) 1 LSB MODULATION CURRENT DAC (SET_IMOD) Full-Scale Current IFS Resolution Integral Nonlinearity Differential Nonlinearity 21 mA 40 A INL 2mA IMOD 12mA 1 LSB DNL 2mA IMOD 12mA, guaranteed monotonic at 8-bit resolution (SET_IMOD[8:1]) 1 LSB CONTROL I/O SPECIFICATIONS RSEL Input Current RSEL Input High Voltage I IH, I IL VIH RSEL Input Low Voltage VIL RSEL Input Impedance RPULL DISABLE Input Current 1.8 0 Internal pulldown resistor 40 75 I IH I IL 150 A VCC V 0.8 V 110 k 12 Dependency on pullup resistance 420 800 A DISABLE Input High Voltage VIH 1.8 VCC V DISABLE Input Low Voltage VIL 0 0.8 V DISABLE Input Impedance RPULL Internal pullup resistor LOS, FAULT Output High Voltage VOH RLOS = 4.7k - 10k to VCC, RFAULT = 4.7k - 10k to VCC LOS, FAULT Output Low Voltage VOL RLOS = 4.7k - 10k to VCC, RFAULT = 4.7k - 10k to VCC 10 k VCC 0.5 4.7 8 VCC V 0 0.4 V 2.0 VCC V 0.8 V 3-WIRE DIGITAL I/O SPECIFICATIONS (SDA, CSEL, SCL) Input High Voltage VIH Input Low Voltage VIL Input Hysteresis VHYST Input Leakage Current I IL, IIH 0.082 VIN = 0V or VCC; internal pullup or pulldown (75k typ) Output High Voltage VOH External pullup of 4.7k to VCC Output Low Voltage VOL External pullup of 4.7k to VCC V 150 VCC 0.5 A V 0.4 V 1000 kHz 3-WIRE DIGITAL INTERFACE TIMING CHARACTERISTICS (See Figure 4) SCL Clock Frequency f SCL SCL Pulse-Width High tCH 0.5 s SCL Pulse-Width Low tCL 0.5 s 6 400 _______________________________________________________________________________________ 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver (VCC = 2.85V to 3.63V, TA = -40C to +85C, CML receiver output load is AC-coupled to differential 100, CAZ = 1nF, transmitter output load is AC-coupled to differential 100 (see Figure 1), typical values are at +25C, VCC = 3.3V, IBIAS = 6mA, IMOD = 6mA, unless otherwise specified. Registers are set to default values unless otherwise noted, and the 3-wire interface is static during measurements. For testing, the RATE_SEL bit was used and the RSEL pin was left open.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS SDA Setup Time tDS 100 ns SDA Hold Time tDH 100 ns SCL Rise to SDA Propagation Time tD 5 ns CSEL Pulse-Width Low tCSW 500 ns CSEL Leading Time Before the First SCL Edge tL 500 ns CSEL Trailing Time After the Last SCL Edge tT 500 ns SDA, SCL External Load CB Total bus capacitance on one line with 4.7k pullup to VCC 20 pF Note 1: Supply current is measured with unterminated receiver CML output or with AC-coupled Rx output termination. The Tx output and the bias current output must be connected to a separate supply to remove the modulation/bias current portion from the supply current. BIAS must be connected to 2.0V. TOUT+/- must be connected through 50 load resistors to a separate supply voltage. Note 2: Guaranteed by design and characterization, TA = -40C to +95C. Note 3: The data input transition time is controlled by a 4th-order Bessel filter with -3dB frequency = 0.75 x data rate. The deterministic jitter caused by this filter is not included in the DJ generation specifications. Note 4: Test pattern is 00001111 at 1.25Gbps for RATE_SEL = 0. Test pattern is 00001111 at 8.5Gbps for RATE_SEL = 1. Note 5: Receiver deterministic jitter is measured with a repeating 231 - 1 PRBS equivalent pattern at 10.32Gbps. For 1.25Gbps to 8.5Gbps, a repeating K28.5 pattern [00111110101100000101] is used. Deterministic jitter is defined as the arithmetic sum of pulse-width distortion (PWD) and pattern-dependent jitter (PDJ). Note 6: Measured with a k28.5 pattern from 1.0625Gbps to 8.5Gbps. Measured with 231 - 1 PRBS at 10.32Gbps. Note 7: Measurement includes an input AC-coupling capacitor of 100nF and CCAZ of 100nF. The signal at the input is switched between two amplitudes: Signal_ON and Signal_OFF. 1) Receiver operates at sensitivity level plus 1dB power penalty. a) Signal_OFF = 0 Signal_ON = (+8dB) + 10log(min_assert_level) b) Signal_ON = (+1dB) + 10log(max_deassert_level) Signal_OFF = 0 2) Receiver operates at overload. Signal_OFF = 0 Signal_ON = 1.2VP-P max_deassert_level and the min_assert_level are measured for one LOS_THRESHOLD setting. Note 8: Gain stability is defined as [(I_measured) - (I_reference)]/(I_reference) over the listed current range, temperature, and VCC from +2.95V to +3.63V. Reference current measured at VCC = +3.2V, TA = +25C. Note 9: Transmitter deterministic jitter is measured with a repeating 27 - 1 PRBS, 72 0s, 27 - 1 PRBS, and 72 1s pattern at 10.32Gbps. For 1.0625Gbps to 8.5Gbps, a repeating K28.5 pattern [00111110101100000101] is used. Deterministic jitter is defined as the arithmetic sum of PWD and PDJ. Note 10: Gain stability is defined as [(I_measured) - (I_reference)]/(I_reference) over the listed current range, temperature, and VCC from +2.85V to +3.63V. Reference current measured at VCC = +3.3V, TA = +25C. _______________________________________________________________________________________ 7 MAX3799 ELECTRICAL CHARACTERISTICS (continued) 1000pF 1nF 50 VCCR 50 0.1F RIN+ VCCR CAZ2 CONTROLLER CAZ1 4.7k 0.1F VCCT RIN- MAX3799 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver VEER LOS VCCR VEET 4.7k RSEL FAULT 50 0.1F 50 OSCILLOSCOPE BIAS ROUT+ 50 50 MAX3799 0.1F CONTROLLER 0.1F 50 TOUT+ ROUT- OSCILLOSCOPE 0.1F 50 CONTROLLER DISABLE BMON TIN- TIN+ CSEL SDA VCCD SCL VCCD VCCT 1000pF 0.1F CONTROLLER 0.1F 0.1F 1k 50 VCCR VCCT 0.1F VCCD 50 1H 50 VCCT 1000pF VCC 50 TOUT- Figure 1. Test Circuit for VCSEL Driver Characterization 8 _______________________________________________________________________________________ 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver 340 RATE_SEL = 1 320 21 19 17 15 13 11 9 7 310 AT 8.5Gbps 5 4 3 AT 10.32Gbps 2 5 300 1 3 200 400 600 800 1000 1200 0 INPUT AMPLITUDE (mVP-P) DETERMINISTIC JITTER vs. DATA RATE PATTERN = k28.5 9 8 BER 7 6 5 RATE_SEL = 1 4 400 600 800 1000 0 1200 200 400 600 800 1000 1200 INPUT AMPLITUDE (mVP-P) INPUT AMPLITUDE (mVP-P) BER vs. INPUT AMPLITUDE OUTPUT EYE DIAGRAM AT 1.25Gbps MAX3799 toc06 1.0E-01 1.0E-02 1.0E-03 MAX3799 toc04 10 200 MAX3799 toc05 0 DETERMINISTIC JITTER (ps) PATTERN = PRBS, RATE_SEL = 1 6 DETERMINISTIC JITTER (ps) 350 7 MAX3799 toc02 PATTERN = k28.5, RATE_SEL = 0 23 DETERMINISTIC JITTER (ps) 360 RANDOM JITTER (ps) 25 MAX3799 toc01 370 330 DETERMINISTIC JITTER vs. INPUT AMPLITUDE DETERMINISTIC JITTER vs. INPUT AMPLITUDE AT 1.25Gbps MAX3799 toc03 RANDOM JITTER vs. INPUT AMPLITUDE RATE_SEL = 0 1.0E-04 1.0E-05 1.0E-06 1.0E-07 1.0E-08 1.0E-09 RATE_SEL = 0 RATE_SEL = 1 150mV/div 1.0E-10 1.0E-11 3 1.0E-12 1.0E-13 2 0 2 4 6 8 10 12 0.5 14 1.0 1.5 2.0 2.5 3.0 200ps/div INPUT AMPLITUDE (mVP-P) DATA RATE (Gbps) OUTPUT EYE DIAGRAM AT 4.25Gbps OUTPUT EYE DIAGRAM AT 10.32Gbps OUTPUT EYE DIAGRAM AT 8.5Gbps MAX3799 toc07 MAX3799 toc09 MAX3799 toc08 RATE_SEL = 1 50mV/div 50mV/div 50mV/div 50ps/div 20ps/div 20ps/div _______________________________________________________________________________________ 9 MAX3799 Typical Operating Characteristics--Limiting Amplifier (VCC = 3.3V, TA = +25C, unless otherwise specified. Figure 1 shows the typical setup used for measurements. Registers are set to default values unless otherwise noted, and the 3-wire interface is static during measurements. For testing, the RATE_SEL bit was used and the RSEL pin was left open.) Typical Operating Characteristics--Limiting Amplifier (continued) (VCC = 3.3V, TA = +25C, unless otherwise specified. Figure 1 shows the typical setup used for measurements. Registers are set to default values unless otherwise noted, and the 3-wire interface is static during measurements. For testing, the RATE_SEL bit was used and the RSEL pin was left open.) TRANSITION TIME LOS THRESHOLD vs. DAC SETTING OUTPUT EYE DIAGRAM AT 14.025Gbps vs. INPUT AMPLITUDE RATE_SEL = 0, RXDE_EN = 0 50 40 30 RATE_SEL = 1, RXDE_EN = 0 20 RATE_SEL = 1, RXDE_EN = 1 10 140 200 0 400 600 120 DEASSERT 100 80 60 40 PATTERN = 00001111 20% TO 80% 0 20ps/div 160 LOS THRESHOLD (mV) TRANSITION TIME (ps) 60 50mV/div 180 MAX3799 toc11 70 MAX3799 toc12 MAX3799 toc10 RATE_SEL = 1, RXDE_EN = 1 800 1000 ASSERT 20 0 0 1200 7 14 21 SENSITIVITY vs. DATA RATE -10 -15 -18 -15 -30 -40 -19 -20 -30 -45 3 5 7 9 11 1G -50 100M 100G 10G 1G 100G 10G DATA RATE (Gbps) FREQUENCY (Hz) FREQUENCY (Hz) CML OUTPUT AMPLITUDE vs. DAC SETTING TOTAL SUPPLY CURRENT vs. TEMPERATURE TOTAL SUPPLY CURRENT vs. TEMPERATURE 800 600 400 110 100 90 80 50 0 40 50 100 150 200 SET_CML[7:0] 250 300 IBIAS = 9mA IBIAS = 2mA 70 60 200 SUPPLY CURRENT (mA) 1000 IBIAS = 12mA 120 SUPPLY CURRENT (mA) 1200 130 MAX3799 toc17 140 MAX3799 toc16 1400 IMOD = 2mA; RECEIVER OUTPUT = 400mVP-P; TOTAL SUPPLY MEASURED USING THE SETUP IN FIGURE 1 -40 -25 -10 5 20 35 50 TEMPERATURE (C) 65 80 95 160 150 140 130 120 110 100 90 80 70 60 50 40 MAX3799 toc18 -60 100M -22 0 -25 -40 RATE_SEL = 0 1 -20 -35 -50 -21 10 -5 SDD22 (dB) -17 63 56 -10 -20 -16 49 MAX3799 toc15 RATE_SEL = 1 SDD11 (dB) SENSITIVITY OMA (dBm) -14 42 0 MAX3799 toc14 USING FINISAR ROSA -13 35 Rx OUTPUT RETURN LOSS Rx INPUT RETURN LOSS 0 MAAX3799 toc13 -12 28 SET_LOS[5:0] INPUT AMPLITUDE (mVP-P) CML OUTPUT AMPLITUDE (mVP-P) MAX3799 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver IMOD = 12mA IMOD = 9mA IMOD = 2mA IBIAS = 2mA; RECEIVER OUTPUT = 400mVP-P; TOTAL SUPPLY MEASURED USING THE SETUP IN FIGURE 1 -40 -25 -10 5 20 35 50 TEMPERATURE (C) ______________________________________________________________________________________ 65 80 95 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver OPTICAL EYE DIAGRAM OPTICAL EYE DIAGRAM MAX3799 toc19 MAX3799 toc21 MAX3799 toc20 8.5Gbps, SET_IMOD = 60, 27 - 1 PRBS, 850nm VCSEL, MASK WITH 54% 4.25Gbps, SET_IMOD = 60, 27 - 1 PRBS, 850nm VCSEL, MASK WITH 46% 2.125Gbps, SET_IMOD = 60, 27 - 1 PRBS, 850nm VCSEL, MASK WITH 50% 68ps/div 34ps/div 17ps/div OPTICAL EYE DIAGRAM ELECTRICAL EYE DIAGRAM DETERMINISTIC JITTER vs. MODULATION CURRENT MAX3799 toc23 MAX3799 toc22 10.3Gbps, SET_IMOD = 60, 27 - 1 PRBS, 850nm VCSEL, MASK WITH 44% 8.0 14.025Gbps, SET_IMOD = 60, 231 - 1 PRBS PATTERN = PRBS, DATA RATE = 10.32Gbps DETERMINISTIC JITTER (ps) 7.5 EYE WIDTH 62.8ps MAX3799 toc24 OPTICAL EYE DIAGRAM 7.0 6.5 6.0 5.5 5.0 4.5 2 14ps/div 14ps/div 4 6 8 10 12 MODULATION CURRENT (mAP-P) RISE TIME 23 18 13 MAX3799 toc26 37 35 FALL TIME 33 31 29 RISE TIME 8 3 4 6 8 10 MODULATION CURRENT (mAP-P) 12 10 RLOAD = 50 8 6 RLOAD = 100 4 0 25 2 RLOAD = 75 12 2 27 PATTERN = 11110000, DATA RATE = 8.5Gbps 14 MODULATION CURRENT (mA) TRANSITION TIME (ps) 28 PATTERN = 11110000, DATA RATE = 8.5Gbps, IMOD = 10mAP-P 39 TRANSITION TIME (ps) FALL TIME 33 41 MAX3799 toc25 38 MODULATION CURRENT vs. DAC SETTING TRANSITION TIME vs. DEEMPHASIS SETTING MAX3799 toc27 TRANSITION TIME vs. MODULATION CURRENT 0 1 2 3 4 5 6 7 SET_TXDE[3:0] 8 9 10 11 0 50 100 150 200 250 300 SET_IMOD[8:0] ______________________________________________________________________________________ 11 MAX3799 Typical Operating Characteristics--VCSEL Driver (continued) (VCC = 3.3V, TA = +25C, unless otherwise specified. Figure 1 shows the typical setup used for measurements. Registers are set to default values unless otherwise noted, and the 3-wire interface is static during measurements. For testing, the RATE_SEL bit was used and the RSEL pin was left open.) Typical Operating Characteristics--VCSEL Driver (continued) (VCC = 3.3V, TA = +25C, unless otherwise specified. Figure 1 shows the typical setup used for measurements. Registers are set to default values unless otherwise noted, and the 3-wire interface is static during measurements. For testing, the RATE_SEL bit was used and the RSEL pin was left open.) BIAS CURRENT vs. DAC SETTING TRANSMITTER DISABLE TRANSMITTER ENABLE MAX3799 toc29 MAX3799 toc28 14 12 BIAS CURRENT (mA) VCC MAX3799 toc30 VCC 3.3V 3.3V 10 tON = 420ns 8 FAULT 6 LOW FAULT HIGH DISABLE DISABLE LOW 4 OUTPUT 2 LOW HIGH LOW OUTPUT 0 50 0 100 150 200 250 300 100ns/div 1s/div SET_IBIAS[8:0] RESPONSE TO FAULT FAULT RECOVERY FREQUENCY ASSERTION OF DISABLE MAX3799 toc31 EXTERNALLY FORCED FAULT LOW FAULT OUTPUT MAX3799 toc33 EXTERNALLY FORCED FAULT VBIAS HIGH FAULT LOW HIGH DISABLE LOW DISABLE EXTERNAL FAULT VBIAS HIGH FAULT MAX3799 toc32 HIGH LOW HIGH DISABLE LOW LOW OUTPUT OUTPUT 1s/div 4s/div 4s/div Tx OUTPUT RETURN LOSS Tx INPUT RETURN LOSS 0 MAX3799 toc34 0 -10 MAX3799 toc35 VBIAS -5 -10 -15 SDD22 (dB) -20 SDD11 (dB) MAX3799 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver -30 -20 -25 -30 -40 -35 -50 -40 -60 100M 1G 10G FREQUENCY (Hz) 12 100G -45 100M 1G 10G FREQUENCY (Hz) ______________________________________________________________________________________ 100G 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver DETERMINISTIC JITTER vs. PULSE-WIDTH SETTING 8 7 6 5 4 DOWN EYE CROSSING 3 700 IBIAS = 12mA MONITOR CURRENT (A) DETERMINISTIC JITTER (ps) 9 MAX3799 toc37 PATTERN = PRBS, DATA RATE = 10.32Gbps UP 800 MAX3799 toc36 10 BIAS MONITOR CURRENT vs. TEMPERATURE 600 500 400 IBIAS = 8mA 300 IBIAS = 2mA 200 100 2 0 -7 -5 -3 -1 1 3 5 7 -40 -25 -10 SET_PWCTRL[3:0] 5 20 35 50 65 80 95 TEMPERATURE (C) Pin Description PIN NAME FUNCTION 1 LOS Loss-of-Signal Output, Open Drain. The default polarity of LOS is high when the level of the input signal is below the preset threshold set by the SET_LOS DAC. Polarity of the LOS function can be inverted by setting LOS_POL = 0. The LOS circuitry can be disabled by setting the bit LOS_EN = 0. 2 RSEL Mode-Select Input, TTL/CMOS. Set the RSEL pin or RATE_SEL bit (set by the 3-wire digital interface) to logic-high for high-bandwidth mode. Setting RSEL and RATE_SEL logic-low for high-gain mode. The RSEL pin is internally pulled down by a 75k resistor to ground. 3, 6, 27, 30 VCCR Power Supply. Provides supply voltage to the receiver block. 4 ROUT+ 5 ROUT- 7 VCCD 8 DISABLE 9 SCL Serial-Clock Input, TTL/CMOS. This pin has a 75k internal pulldown. 10 SDA Serial-Data Bidirectional Input, TTL/CMOS. Open-drain output. This pin has a 75k internal pullup, but it requires an external 4.7k pullup resistor to meet the 3-wire digital timing specification. (Data line collision protection is implemented.) 11 CSEL Chip-Select Input, TTL/CMOS. Setting CSEL to logic-high starts a cycle. Setting CSEL to logic-low ends the cycle and resets the control state machine. Internally pulled down by a 75k resistor to ground. 12, 15, 18, 21, 24, 25 VCCT Power Supply. Provides supply voltage to the transmitter block. 13 TIN+ Noninverted Transmit Data Input, CML Noninverted Receive Data Output, CML. Back-terminated for 50 load. Inverted Receive Data Output, CML. Back-terminated for 50 load. Power Supply. Provides supply voltage for the digital block. Transmitter Disable Input, TTL/CMOS. Set to logic-low for normal operation. Logic-high or open disables both the modulation and bias current. Internally pulled up by an 8k resistor to VCCT. ______________________________________________________________________________________ 13 MAX3799 Typical Operating Characteristics--VCSEL Driver (continued) (VCC = 3.3V, TA = +25C, unless otherwise specified. Figure 1 shows the typical setup used for measurements. Registers are set to default values unless otherwise noted, and the 3-wire interface is static during measurements. For testing, the RATE_SEL bit was used and the RSEL pin was left open.) 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver MAX3799 Pin Description (continued) PIN NAME 14 TIN- 16 BMON 17 VEET FUNCTION Inverted Transmit Data Input, CML Bias Current Monitor Output. Current out of this pin develops a ground-referenced voltage across an external resistor that is proportional to the laser bias current. Ground. Provides ground for the transmitter block. 19 TOUT- Inverted Modulation Current Output. Back-termination of 50 to VCCT. 20 TOUT+ Noninverted Modulation Current Output. Back-termination of 50 to VCCT. 22 BIAS 23 FAULT 26 VEER 28 RIN- Inverted Receive Data Input, CML 29 RIN+ Noninverted Receive Data Input, CML 31 CAZ2 Offset Correction Loop Capacitor. A capacitor connected between this pin and CAZ1 sets the time constant of the offset correction loop. The offset correction can be disabled through the digital interface by setting the bit AZ_EN = 0. 32 CAZ1 Offset Correction Loop Capacitor. Counterpart to CAZ2, internally connected to VEER . -- EP VCSEL Bias Current Output Transmitter Fault Output, Open Drain. Logic-high indicates a fault condition. FAULT remains high even after the fault condition has been removed. A logic-low occurs when the fault condition has been removed and the fault latch has been cleared by the DISABLE signal. Ground. Provides ground for the receiver block. Exposed Pad. Ground. Must be soldered to circuit board ground for proper thermal and electrical performance (see the Exposed-Pad Package section). Detailed Description The MAX3799 SFP+ transceiver combines a limiting amplifier receiver with loss-of-signal detection and a VCSEL laser driver transmitter with fault protection. Configuration of the advanced Rx and Tx settings of the MAX3799 is performed by a controller through the 3-wire interface. The MAX3799 provides multiple current and voltage DACs to allow the use of low-cost controller ICs. 14 Limiting Amplifier Receiver The limiting amplifier receiver inside the MAX3799 is designed to operate from 1.0625Gbps to 10.32Gbps. The receiver includes a dual path limiter, offset correction circuitry, CML output stage with deemphasis, and loss-of-signal circuitry. The functions of the receiver can be controlled through the on-chip 3-wire interface. The registers that control the receiver functionality are RXCTRL1, RXCTRL2, RXSTAT, MODECTRL, SET_CML, and SET_LOS. ______________________________________________________________________________________ 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver MAX3799 CAZ2 CAZ1 OFFSET CORRECTION 10.32Gbps LIMITING AMPLIFIER AZ_EN RXDE_EN 1G 900MHz RIN+ 0 1 ROUT+ 0 ROUT- 1 RIN- RX_POL LOS_POL LOS_EN RSEL RATE_SEL RPULL LOS OUTPUT CONTROL LOGIC SQ_EN LOS VEER VCCD SCL SDA CSEL 3-WIRE INTERFACE RPULL RPULL INTERNAL REGISTER 6b DAC SET_LOS RPULL CONTROL LOGIC 8b DAC SET_CML 9b DAC SET_IMOD 9b DAC SET_IBIAS 4b DAC SET_PWCTRL 4b DAC SET_TXDE BMON IBIAS BIAS BIAS MONITOR IMOD IDE TX_POL IVCSEL = IMOD - IDE TOUT+ PULSEWIDTH CONTROL TOUT- 1 TIN+ 0 TINVCCT RPULL FAULT EYE SAFETY AND OUTPUT CONTROL TX_EN DISABLE POWER-ON RESET MAX3799 10.32Gbps VCSEL DRIVER Figure 2. Functional Diagram ______________________________________________________________________________________ 15 MAX3799 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver Dual Path Limiter The limiting amplifier features a low data-rate mode (1.25Gbps) and a high data-rate mode (up to 10.32Gbps), allowing for overall system optimization. Either the RSEL pin or the RATE_SEL bit can perform the rate selection. For operating up to 1.25Gbps, the low data-rate mode (RATE_SEL = 0) is recommended. For operation up to 14.025Gbps, the high data-rate mode (RATE_SEL = 1) is recommended. The polarity of the ROUT+/ROUT- relative to RIN+/RIN- is programmed by the RX_POL bit. Offset Correction Circuitry The offset correction circuit is enabled to remove pulsewidth distortion caused by intrinsic offset voltages within the differential amplifier stages. An external capacitor (CAZ) connected between the CAZ1 and CAZ2 pins is used to set the offset correction loop cutoff frequency. The offset loop can be disabled using the AZ_EN bit. CML Output Stage with Deemphasis and Slew-Rate Control The CML output stage is optimized for differential 100 loads. The RXDE_EN bit adds analog deemphasis compensation to the limited differential output signal for SFP connector losses. The output stage is controlled by a combination of the RX_EN and SQ_EN bits and the LOS pin. See Table 1. Amplitude of the CML output stage is controlled by an 8-bit DAC register (SET_CML). The differential output amplitude range is from 40mVP-P up to 1200mVP-P with 4.6mVP-P resolution (assuming an ideal 100 differential load). Table 1. CML Output Stage Operation Mode OPERATION MODE DESCRIPTION RX_EN SQ_EN LOS 0 X X CML output disabled. 1 0 X CML output enabled. 1 1 0 CML output enabled. 1 1 1 CML output disabled. 16 Loss-of-Signal (LOS) Circuitry The input data amplitude is compared to a preset threshold controlled by the 6-bit DAC register SET_LOS. The LOS assert level can be programmed from 14mVP-P up to 77mVP-P with 1.5mVP-P resolution (assuming an ideal 100 differential source). LOS is enabled through the LOS_EN bit and the polarity of the LOS is controlled with the LOS_POL bit. VCSEL Driver The VCSEL driver inside the MAX3799 is designed to operate from 1.0625Gbps to 10.32Gbps. The transmitter contains a differential data path with pulse-width adjustment, bias current and modulation current DACs, output driver with programmable deemphasis, poweron reset circuitry, BIAS monitor, VCSEL current limiter, and eye safety circuitry. A 3-wire digital interface is used to control the transmitter functions. The registers that control the transmitter functionality are TXCTRL, TXSTAT1, TXSTAT2, SET_IBIAS, SET_IMOD, IMODMAX, IBIASMAX, MODINC, BIASINC, MODECTRL, SET_PWCTRL, and SET_TXDE. Differential Data Path The CML input buffer is optimized for AC-coupled signals and is internally terminated with a differential 100. Differential input data is equalized for high-frequency losses due to SFP connectors. The TX_POL bit in the TXCTRL register controls the polarity of TOUT+ and TOUT- vs. TIN+ and TIN-. The SET_PWCTRL register controls the output eye-crossing adjustment. A status indicator bit (TXED) monitors the presence of an AC input signal. Table 2. Slew-Rate Control for CML Output Stage RATE_SEL OPERATION MODE DESCRIPTION 0 1.25Gbps operation with reduced output edge speed. 1 Up to 10.32Gbps operation. ______________________________________________________________________________________ 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver The value of the SET_IBIAS DAC register is updated when the BIASINC register is addressed through the 3-wire interface. The BIASINC register is an 8-bit register where the first 5 bits contain the increment information in two's complement notation. Increment values range from -8 to +7 LSBs. If the updated value of SET_IBIAS[8:1] exceeds IBIASMAX[7:0], the IBIASERR warning flag is set and SET_IBIAS[8:0] remains unchanged. Modulation Current DAC The modulation current from the MAX3799 is optimized to provide up to 12mA of modulation current into a 100 differential load with 40A resolution. The modulation current is controlled through the 3-wire digital interface using the SET_IMOD, IMODMAX, MODINC, and SET_TXDE registers. For VCSEL operation, the IMODMAX register is first programmed to a desired maximum modulation current value (up to 12mA into a 100 differential load). The modulation current to the VCSEL then can range from zero to the value programmed into the IMODMAX register. The modulation current level is stored in the 9-bit SET_IMOD register. Only bits 1 to 8 are written to. The LSB (bit 0) of SET_IMOD is initialized to zero and is updated through the MODINC register. The value of the SET_IMOD DAC register is updated when the MODINC register is addressed through the 3-wire interface. The MODINC register is an 8-bit register where the first 5 bits contain the increment information in two's complement notation. Increment values range from -8 to +7 LSBs. If the updated value of SET_IMOD[8:1] exceeds IMODMAX[7:0], the IMODERR warning flag is set and SET_IMOD[8:0] remains unchanged. Output Driver The output driver is optimized for an AC-coupled 100 differential load. The output stage also features programmable deemphasis that allows the deemphasis amplitude to be set as a percentage of the modulation current. The deemphasis function is enabled by the TXDE_EN bit. At initial setup, the required amount of deemphasis can be set using the SET_TXDE register. During the system operation, it is advised to use the incremental mode that updates the deemphasis (SET_TXDE) and the modulation current DAC (SET_IMOD) simultaneously through the MODINC register. Power-On Reset (POR) Power-on reset ensures that the laser is off until the supply voltage has reached a specified threshold (2.55V). After power-on reset, bias current and modulation current ramp up slowly to avoid an overshoot. In the case of a POR, all registers are reset to their default values. Bias Current Monitor Current out of the BMON pin is typically 1/16th the value of IBIAS. A resistor to ground at BMON sets the voltage gain. An internal comparator latches a SOFT FAULT if the voltage on BMON exceeds the value of VCC - 0.55V. Eye Safety and Output Control Circuitry The safety and output control circuitry contains a disable pin (DISABLE) and disable bit (TX_EN), along with a FAULT indicator and fault detectors (Figure 3). The MAX3799 has two types of faults, HARD FAULT and SOFT FAULT. A HARD FAULT triggers the FAULT pin and the output to the VCSEL is disabled. A SOFT FAULT operates more like a warning and the outputs are not disabled. Both types of faults are stored in the TXSTAT1 and TXSTAT2 registers. The FAULT pin is a latched output that can be cleared by toggling the DISABLE pin. Toggling the DISABLE pin also clears the TXSTAT1 and TXSTAT2 registers. A single-point fault can be a short to VCC or GND. Table 3 shows the circuit response to various single-point failures. ______________________________________________________________________________________ 17 MAX3799 Bias Current DAC The bias current from the MAX3799 is optimized to provide up to 15mA of bias current into a 50 to 75 VCSEL load with 40A resolution. The bias current is controlled through the 3-wire digital interface using the SET_IBIAS, IBIASMAX, and BIASINC registers. For VCSEL operation, the IBIASMAX register is first programmed to a desired maximum bias current value (up to 15mA). The bias current to the VCSEL then can range from zero to the value programmed into the IBIASMAX register. The bias current level is stored in the 9-bit SET_IBIAS register. Only bits 1 to 8 are written to. The LSB (bit 0) of SET_IBIAS is initialized to zero and is updated through the BIASINC register. MAX3799 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver VCCT FAULT REGISTER TXSTAT1 TOUT- TOUT+ <0> FAULT BIAS <1> 0.72V IMOD <2> 0.8V IBIAS <3> 1.5V FAULT REGISTER TXSTAT1 IBIAS 16 <4> <5> <6> VCC - 0.55V BMON <7> VCCT POR POR RESET 8k DISABLE UNUSED LOSS-OF-SIGNAL CIRCUIT WARNING REGISTER TXSTAT2 <0> ADDR7 <1> TX_LOS BIAS INCREMENT <2> BIASMAX MOD INCREMENT <3> MODMAX Figure 3. Eye Safety Circuitry 18 ______________________________________________________________________________________ 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver PIN NAME 1 LOS Normal (Note 1) SHORT TO VCC 2 RSEL SHORT TO GND OPEN Normal (Note 1) Normal (Note 1) Normal (Note 1) Normal (Note 1) Normal (Note 1) Normal Disabled--HARD FAULT (external Normal (Note 3)--Redundant path supply shorted) (Note 2) 3 VCCR 4 ROUT+ Normal (Note 1) Normal (Note 1) Normal (Note 1) 5 ROUT- Normal (Note 1) Normal (Note 1) Normal (Note 1) 6 VCCR Normal Disabled--HARD FAULT (external Normal (Note 3)--Redundant path supply shorted) (Note 2) 7 VCCD Normal Disabled--HARD FAULT Disabled--HARD FAULT Normal (Note 1). Can only be disabled with other means. Disabled 8 DISABLE Disabled 9 SCL Normal (Note 1) Normal (Note 1) Normal (Note 1) 10 SDA Normal (Note 1) Normal (Note 1) Normal (Note 1) 11 CSEL Normal (Note 1) Normal (Note 1) Normal (Note 1) Normal Disabled--Fault (external supply shorted) (Note 2) Normal (Note 3)--Redundant path 12 VCCT 13 TIN+ SOFT FAULT SOFT FAULT Normal (Note 1) 14 TIN- SOFT FAULT SOFT FAULT Normal (Note 1) 15 VCCT Normal Disabled--Fault (external supply shorted) (Note 2) Normal (Note 3)--Redundant path 16 BMON Disabled--HARD FAULT Normal (Note 1) Disabled--HARD FAULT 17 VEET Disabled--Fault (external supply shorted) (Note 2) Normal Disabled--HARD FAULT 18 VCCT Normal Disabled--Fault (external supply shorted) (Note 2) Normal (Note 3)--Redundant path 19 TOUT- IMOD is reduced Disabled--HARD FAULT IMOD is reduced 20 TOUT+ IMOD is reduced Disabled--HARD FAULT IMOD is reduced 21 VCCT Normal Disabled--Fault (external supply shorted) (Note 2) Normal (Note 3)--Redundant path 22 BIAS IBIAS is on--No Fault Disabled--HARD FAULT Disabled--HARD FAULT 23 FAULT Normal (Note 1) Normal (Note 1) Normal (Note 1) Normal (Note 3)--Redundant path 24 VCCT Normal Disabled--Fault (external supply shorted) (Note 2) 25 VCCT Normal Disabled--Fault (external supply shorted) (Note 2) Normal (Note 3)--Redundant path 26 VEER Disabled--Fault (external supply shorted) (Note 2) Normal Normal (Note 3)--Redundant path 27 VCCR Normal Disabled--HARD FAULT (external Normal (Note 3)--Redundant path supply shorted) (Note 2) 28 RIN- Normal (Note 1) Normal (Note 1) Normal (Note 1) 29 RIN+ Normal (Note 1) Normal (Note 1) Normal (Note 1) ______________________________________________________________________________________ 19 MAX3799 Table 3. Circuit Response to Single-Point Faults MAX3799 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver Table 3. Circuit Response to Single-Point Faults (continued) PIN NAME SHORT TO VCC SHORT TO GND OPEN 30 VCCR Normal Disabled--Fault (external supply shorted) (Note 2) Normal (Note 3)--Redundant path 31 CAZ2 Normal (Note 1) Normal (Note 1) Normal (Note 1) 32 CAZ1 (VEER) Disabled--Fault (external supply shorted) (Note 2) Normal (Note 3)--Redundant path Normal (Note 3)--Redundant path Note 1: Normal--Does not affect laser power. Note 2: Supply-shorted current is assumed to be primarily on the circuit board (outside this device) and the main supply is collapsed by the short. Note 3: Normal in functionality, but performance could be affected. Warning: Shorted to VCC or shorted to ground on some pins can violate the Absolute Maximum Ratings. Read Mode (RWN = 1) The master generates 16 clock cycles at SCL in total. The master outputs a total of 8 bits (MSB first) to the SDA line at the falling edge of the clock. The SDA line is released after the RWN bit has been transmitted. The slave outputs 8 bits of data (MSB first) at the rising edge of the clock. The master closes the transmission by setting CSEL to 0. Figure 4 shows the interface timing. 3-Wire Digital Communication The MAX3799 implements a proprietary 3-wire digital interface. An external controller generates the clock. The 3-wire interface consists of an SDA bidirectional data line, an SCL clock signal input, and a CSEL chip-select input (active high). The external master initiates a data transfer by asserting the CSEL pin. The master starts to generate a clock signal after the CSEL pin has been set to 1. All data transfers are most significant bit (MSB) first. Mode Control Normal mode allows read-only instruction for all registers except MODINC and BIASINC. The MODINC and BIASINC registers can be updated during normal mode. Doing so speeds up the laser control update through the 3-wire interface by a factor of two. The normal mode is the default mode. Setup mode allows the master to write unrestricted data into any register except the status (TXSTAT1, TXSTAT2, and RXSTAT) registers. To enter the setup mode, the MODECTRL register (address = H0x0E) must be set to H0x12. After the MODECTRL register has been set to H0x12, the next operation is unrestricted. The setup mode is automatically exited after the next operation is finished. This sequence must be repeated if further unrestricted settings are necessary. Protocol Each operation consists of 16-bit transfers (15-bit address/data, 1-bit RWN). The bus master generates 16 clock cycles to SCL. All operations transfer 8 bits to the MAX3799. The RWN bit determines if the cycle is read or write. See Table 4. Register Addresses The MAX3799 contains 17 registers available for programming. Table 5 shows the registers and addresses. Write Mode (RWN = 0) The master generates 16 clock cycles at SCL in total. The master outputs a total of 16 bits (MSB first) to the SDA line at the falling edge of the clock. The master closes the transmission by setting CSEL to 0. Figure 4 shows the interface timing. Table 4. Digital Communication Word Structure BIT 15 14 13 12 11 Register Address 20 10 9 8 RWN 7 6 5 4 3 2 Data that is written or read. ______________________________________________________________________________________ 1 0 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver ADDRESS NAME H0x00 RXCTRL1 H0x01 RXCTRL2 H0x02 RXSTAT H0x03 SET_CML Output CML Level Setting Register H0x04 SET_LOS LOS Threshold Level Setting Register H0x05 TXCTRL Transmitter Control Register H0x06 TXSTAT1 Transmitter Status Register 1 H0x07 TXSTAT2 Transmitter Status Register 2 H0x08 SET_IBIAS Bias Current Setting Register MAX3799 Table 5. Register Descriptions and Addresses FUNCTION Receiver Control Register 1 Receiver Control Register 2 Receiver Status Register H0x09 SET_IMOD Modulation Current Setting Register H0x0A IMODMAX Maximum Modulation Current Setting Register H0x0B IBIASMAX Maximum Bias Current Setting Register H0x0C MODINC Modulation Current Increment Setting Register H0x0D BIASINC Bias Current Increment Setting Register H0x0E MODECTRL H0x0F SET_PWCTRL Transmitter Pulse-Width Control Register H0x10 SET_TXDE Transmitter Deemphasis Control Register Mode Control Register WRITE MODE CSEL tL tT tCH tCL SCL 0 1 2 3 4 5 6 7 8 9 A4 A3 A2 A1 A0 RWN D7 D6 10 11 12 13 14 15 tDS SDA A6 A5 D5 D4 D3 D2 D1 D0 tDH READ MODE CSEL tL tT tCH tCL SCL 0 1 2 3 4 5 6 7 8 9 tDS SDA A6 A5 A4 10 11 12 13 14 15 tD A3 A2 A1 A0 RWN D7 D6 D5 D4 D3 D2 D1 D0 tDH Figure 4. Timing for 3-Wire Digital Interface ______________________________________________________________________________________ 21 MAX3799 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver Register Descriptions Receiver Control Register 1 (RXCTRL1) Bit # 7 6 5 4 3 2 1 0 Name X X X X X X RATE_SEL X Default Value X X X X X X 0 X ADDRESS H0x00 Bit 1: RATE_SEL. RATE_SEL combined with the RSEL pin through a logic-OR function selects between the low data-rate mode (1.25Gbps) or high data-rate mode (up to 10.32Gbps). Logic-OR output 0 = 1Gbps mode Logic-OR output 1 = 10Gbps mode Receiver Control Register 2 (RXCTRL2) Bit # 7 6 5 4 3 2 1 0 Name X LOS_EN LOS_POL RX_POL SQ_EN RX_EN RXDE_EN AZ_EN Default Value X 1 1 1 0 1 0 1 ADDRESS H0x01 Bit 6: LOS_EN. Controls the LOS circuitry. When RX_EN is set to 0, the LOS detector is also disabled. 0 = disabled 1 = enabled Bit 5: LOS_POL. Controls the output polarity of the LOS pin. 0 = inverse 1 = normal Bit 4: RX_POL. Controls the polarity of the receiver signal path. 0 = inverse 1 = normal Bit 3: SQ_EN. When SQ_EN = 1, the LOS controls the output circuitry. 0 = disabled 1 = enabled Bit 2: RX_EN. Enables or disables the receive circuitry. 0 = disabled 1 = enabled Bit 1: RXDE_EN. Enables or disables the deemphasis on the receiver output. 0 = disabled 1 = enabled Bit 0: AZ_EN. Enables or disables the autozero circuitry. When RX_EN is set to 0, the autozero circuitry is also disabled. 0 = disabled 1 = enabled 22 ______________________________________________________________________________________ 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver Bit # 7 6 5 4 3 2 1 0 (STICKY) Name X X X X X X X LOS Default Value X X X X X X X X ADDRESS H0x02 Bit 0: LOS. Copy of the LOS output circuitry. This is a sticky bit, which means that it is cleared on a read. The first 0-to-1 transition gets latched until the bit is read by the master or POR occurs. Output CML Level Setting Register (SET_CML) Bit # Name Default Value 7 6 5 4 3 2 1 0 SET_CML[0] SET_CML[7] SET_CML[6] SET_CML[5] SET_CML[4] SET_CML[3] SET_CML[2] SET_CML[1] (LSB) (MSB) 0 1 0 1 0 0 1 ADDRESS H0x03 1 Bits 7 to 0: SET_CML[7:0]. The SET_CML register is an 8-bit register that can be set up to 255, corresponding to an output up to 1000mVP-P. See the Typical Operating Characteristics section for a typical CML output voltage vs. DAC code graph. LOS Threshold Level Setting Register (SET_LOS) Bit # 7 6 5 SET_LOS[4] SET_LOS[3] 0 1 Name X X SET_LOS[5] (MSB) Default Value X X 0 4 3 2 1 0 ADDRESS SET_LOS[2] SET_LOS[1] SET_LOS[0] (LSB) H0x04 1 0 0 Bits 5 to 0: SET_LOS[5:0]. The SET_LOS register is a 6-bit register used to program the LOS threshold. See the Typical Operating Characteristics section for a typical LOS threshold voltage vs. DAC code graph. ______________________________________________________________________________________ 23 MAX3799 Receiver Status Register (RXSTAT) MAX3799 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver Transmitter Control Register (TXCTRL) Bit # 7 6 5 4 3 2 1 0 Name X X X X TXDE_EN SOFTRES TX_POL TX_EN Default Value X X X X 0 0 1 1 ADDRESS H0x05 Bit 3: TXDE_EN. Enables or disables the transmit output deemphasis circuitry. 0 = disabled 1 = enabled Bit 2: SOFTRES. Resets all registers to their default values. 0 = normal 1 = reset Bit 1: TX_POL. Controls the polarity of the transmit signal path. 0 = inverse 1 = normal Bit 0: TX_EN. Enables or disables the transmit circuitry. 0 = disabled 1 = enabled Transmitter Status Register 1 (TXSTAT1) Bit # 7 (STICKY) 6 (STICKY) 5 (STICKY) 4 (STICKY) 3 (STICKY) 2 (STICKY) 1 (STICKY) 0 (STICKY) Name FST[7] FST[6] X X FST[3] FST[2] FST[1] TX_FAULT X X X X X X X X Default Value ADDRESS H0x06 Bit 7: FST[7]. When the VCCT supply voltage is below 2.45V, the POR circuitry reports a FAULT. Once the VCCT supply voltage is above 2.55V, the POR resets all registers to their default values and the FAULT is cleared. Bit 6: FST[6]. When the voltage at BMON is above VCC - 0.55V, a SOFT FAULT is reported. Bit 3: FST[3]. When the common-mode voltage at VTOUT+/- goes below 1.5V, a SOFT FAULT is reported. Bit 2: FST[2]. When the voltage at VTOUT+/- goes below 0.8V, a HARD FAULT is reported. Bit 1: FST[1]. When the BIAS voltage goes below 0.44V, a HARD FAULT is reported. Bit 0: TX_FAULT. Copy of a FAULT signal in FST[7] to FST[1]. A POR resets FST[7:1] to 0. Transmitter Status Register 2 (TXSTAT2) Bit # 7 6 5 4 3 (STICKY) 2 (STICKY) 1 (STICKY) 0 (STICKY) Name X X X X IMODERR IBIASERR TXED X Default Value X X X X X X X X ADDRESS H0x07 Bit 3: IMODERR. When the modulation-incremented result is greater than IMODMAX, a SOFT FAULT is reported. See the Programming Modulation Current section. 24 ______________________________________________________________________________________ 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver Bias Current Setting Register (SET_IBIAS) Bit # Name Default Value 7 6 5 4 3 SET_IBIAS SET_IBIAS SET_IBIAS SET_IBIAS SET_IBIAS [8] (MSB) [7] [6] [5] [4] 0 0 0 0 0 2 1 0 SET_IBIAS SET_IBIAS SET_IBIAS [3] [2] [1] 1 0 ADDRESS H0x08 0 Bits 7 to 0: SET_IBIAS[8:1]. The bias current DAC is controlled by a total of 9 bits. The SET_IBIAS[8:1] bits are used to set the bias current with even denominations from 0 to 510 bits. The LSB (SET_IBIAS[0]) bit is controlled by the BIASINC register and is used to set the odd denominations in the SET_IBIAS[8:0]. Modulation Current Setting Register (SET_IMOD) Bit # Name Default Value 7 6 5 4 3 2 1 0 SET_IMOD SET_IMOD SET_IMOD SET_IMOD SET_IMOD SET_IMOD SET_IMOD SET_IMOD [8] (MSB) [7] [6] [5] [4] [3] [2] [1] 0 0 0 1 0 0 1 ADDRESS H0x09 0 Bits 7 to 0: SET_IMOD[8:1]. The modulation current DAC is controlled by a total of 9 bits. The SET_IMOD[8:1] bits are used to set the modulation current with even denominations from 0 to 510 bits. The LSB (SET_IMOD[0]) bit is controlled by the MODINC register and is used to set the odd denominations in the SET_IMOD[8:0]. Maximum Modulation Current Setting Register (IMODMAX) Bit # 7 6 5 4 3 2 1 0 ADDRESS Name IMODMAX [7] (MSB) IMODMAX [6] IMODMAX [5] IMODMAX [4] IMODMAX [3] IMODMAX [2] IMODMAX [1] IMODMAX [0] (LSB) H0x0A 0 0 1 1 0 0 0 0 Default Value Bits 7 to 0: IMODMAX[7:0]. The IMODMAX register is an 8-bit register that can be used to limit the maximum modulation current. IMODMAX[7:0] is continuously compared to the SET_IMOD[8:1]. Maximum Bias Current Setting Register (IBIASMAX) Bit # 7 6 5 4 3 2 1 0 ADDRESS Name IBIASMAX [7] (MSB) IBIASMAX [6] IBIASMAX [5] IBIASMAX [4] IBIASMAX [3] IBIASMAX [2] IBIASMAX [1] IBIASMAX [0] (LSB) H0x0B 0 0 0 1 0 0 1 0 Default Value Bits 7 to 0: IBIASMAX[7:0]. The IBIASMAX register is an 8-bit register that can be used to limit the maximum bias current. IBIASMAX[7:0] is continuously compared to the SET_IBAS[8:1]. ______________________________________________________________________________________ 25 MAX3799 Bit 2: IBIASERR. When the bias incremented result is greater than IBIASMAX, then a SOFT FAULT is reported. See the Programming Bias Current section. Bit 1: TXED. This only indicates the absence of an AC signal at the transmit input. This is not an LOS indicator. MAX3799 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver Modulation Current Increment Setting Register (MODINC) Bit # 7 6 5 Name SET_IMOD [0] X DE_INC 0 0 0 Default Value 4 3 2 1 0 MODINC[0] MODINC[4] MODINC[3] MODINC[2] MODINC[1] (LSB) (MSB) 0 0 0 0 ADDRESS H0x0C 0 Bit 7: SET_IMOD[0]. This is the LSB of the SET_IMOD[8:0] bits. This bit can only be updated by the use of MODINC[4:0]. Bit 5: DE_INC. When this bit is set to 1 and the deemphasis on the transmit output is enabled, the SET_TXDE[3:0] is incremented or decremented by 1 LSB. The increment or decrement is determined by the sign bit of the MODINC[4:0] string of bits. Bits 4 to 0: MODINC[4:0]. This string of bits is used to increment or decrement the modulation current. When written to, the SET_IMOD[8:0] bits are updated. MODINC[4:0] are a two's complement string. Bias Current Increment Setting Register (BIASINC) Bit # 7 Name SET_IBIAS [0] X X 0 0 0 Default Value 6 5 4 3 2 1 0 BIASINC[0] BIASINC[4] BIASINC[3] BIASINC[2] BIASINC[1] (LSB) (MSB) 0 0 0 0 ADDRESS H0x0D 0 Bit 7: SET_IBIAS[0]. This is the LSB of the SET_IBIAS[8:0] bits. This bit can only be updated by the use of BIASINC[4:0]. Bits 4 to 0: BIASINC[4:0]. This string of bits is used to increment or decrement the bias current. When written to, the SET_IBIAS[8:0] bits are updated. BIASINC[4:0] are a two's complement string. Mode Control Register (MODECTRL) Bit # 7 Name Default Value 6 5 4 3 2 1 0 MODECTRL MODECTRL MODECTRL MODECTRL MODECTRL MODECTRL MODECTRL MODECTRL [7] (MSB) [6] [5] [4] [3] [2] [1] [0] (LSB) 0 0 0 0 0 0 0 ADDRESS H0x0E 0 Bits 7 to 0: MODECTRL[7:0]. The MODECTRL register enables a switch between normal and setup modes. The setup mode is achieved by setting this register to H0x12. MODECTRL must be updated before each write operation. Exceptions are MODINC and BIASINC, which can be updated in normal mode. Transmitter Pulse-Width Control Register (SET_PWCTRL) Bit # 7 6 5 4 Name X X X X Default Value X X X X 3 2 1 0 SET_ SET_ SET_ SET_ PWCTRL[3] PWCTRL[0] PWCTRL[2] PWCTRL[1] (MSB) (LSB) 0 0 0 ADDRESS H0x0F 0 Bits 3 to 0: SET_PWCTRL[3:0]. This is a 4-bit register used to control the eye crossing by adjusting the pulse width. 26 ______________________________________________________________________________________ 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver Bit # 7 6 5 4 3 2 1 0 ADDRESS Name X X X X SET_TXDE [3] (MSB) SET_TXDE [2] SET_TXDE [1] SET_TXDE [0] (LSB) H0x10 Default Value X X X X 0 0 0 0 Bits 3 to 0: SET_TXDE[3:0]. This is a 4-bit register used to control the amount of deemphasis on the transmitter output. When calculating the total modulation current, the amount of deemphasis must be taken into account. The deemphasis is set as a percentage of modulation current. Design Procedure Programming Bias Current 1) IBIASMAX[7:0] = Maximum_Bias_Current_Value 2) SET_IBIASi[8:1] = Initial_Bias_Current_Value Note: The total bias current value is calculated using the SET_IBIAS[8:0] register. SET_IBIAS[8:1] are the bits that can be manually written. SET_IBIAS[0] can only be updated using the BIASINC[4:0] register. When implementing an APC loop, it is recommended to use the BIASINC[4:0] register, which guarantees the fastest bias current update. 3) BIASINCi[4:0] = New_Increment_Value 4) If (SET_IBIASi[8:1] IBIASMAX[7:0]), then (SET_IBIASi[8:0] = SET_IBIASi-1[8:0] + BIASINCi[4:0]) 5) Else (SET_IBIASi[8:0] = SET_IBIASi-1[8:0]) The total bias current can be calculated as follows: 6) IBIAS = [SET_IBIASi[8:0] + 20] x 40A Programming Modulation Current 1) IMODMAX[7:0] = Maximum_Modulation_Current_Value 2) SET_IMODi[8:1] = Initial_Modulation_Current_Value Note: The total modulation current value is calculated using the SET_IMOD[8:0] register. SET_IMOD[8:1] are the bits that can be manually written. SET_IMOD[0] can only be updated using the MODINC[4:0] register. When implementing modulation compensation, it is recommended to use the MODINC[4:0] register, which guarantees the fastest modulation current update. 3) MODINCi[4:0] = New_Increment_Value 4) If (SET_IMODi[8:1] IMODMAX[7:0]), then (SET_IMODi[8:0] = SET_IMODi-1[8:0] + MODINCi[4:0]) 5) Else (SET_IMODi[8:0] = SET_IMODi-1[8:0]) The following equation is valid with assumption of 100 on-chip and 100 external differential load (Rextd). The maximum value that can be set for SET_TXDE[3:0] = 11. 6) IMOD(Rextd=100) = [(20 + SET_IMODi[8:0]) x 40A] 2 + SET _ TXDE[3 : 0] x 1 - 64 For general Rextd, the modulation current that is achieved using the same setting of SET_IMODi[8:0] as for Rextd = 100 is shown below. It can be written as a function of IMOD(Rextd=100), still assuming a 100 onchip load. Re xt 7) IMOD(Re xtd) = 2 x IMOD (Re xtd=100) Re xt + 100 Programming LOS Threshold LOSTH = (SET_LOS[5:0] x 1.5mVP-P) Programming Transmit Output Deemphasis The TXDE_EN bit must be set to 1 to enable the deemphasis function. The SET_TXDE register value is used to set the amount of deemphasis, which is a percentage of the modulation current. Deemphasis percentage is determined as: DE(%) = 100 x ( 2 + SET _ TXDE[3 : 0] ) 64 where the maximum SET_TXDE[3:0] = 11. For an IMOD value of 10mA, the maximum achievable deemphasis value is approximately 20%. Maximum deemphasis achievable for full IMOD range of 12mA is limited to 15%. With deemphasis enabled, the value of the modulation current amplitude is reduced by the calculated deemphasis percentage. To maintain the modulation current amplitude constant, the SET_IMOD[8:0] register must be increased by the deemphasis percentage. If the system conditions like temperature, required IMOD value, etc., change during the transmit operation, the deemphasis setting might need to be readjusted. For such an ______________________________________________________________________________________ 27 MAX3799 Transmitter Deemphasis Control Register (SET_TXDE) MAX3799 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver impromptu deemphasis adjustment, it is recommended that the DE_INC (MODINC[5]) bit is used. Use of this bit increments or decrements the deemphasis code setting by 1 LSB based on the sign of increment in the MODINC[4:0] and, hence, the SET_IMOD[8:0] setting. This helps maintain the BER while having the flexibility to improve signal quality by adjusting deemphasis while the transmit operation continues. This feature enables glitchless deemphasis adjustment while maintaining excellent BER performance. Activating Receiver Output Deemphasis The RXDE_EN bit must be set to 1 to enable the deemphasis function. Deemphasis decreases the output amplitude at ROUT+/ROUT- by 25%. To maintain the same output amplitude as before the activation of deemphasis, the SET_CML register value needs to be increased by 25%. When deemphasis is enabled, the limiting amplifier AC performance is guaranteed up to 800mVP-P typical output amplitude. The SET_CML register can be set from 0 to 255 bits, but it is important to note that performance is guaranteed up to 215 bits. Programming Pulse-Width Control The eye crossing at the Tx output can be adjusted using the SET_PWCTRL register. Table 6 shows these settings. The sign of the number specifies the direction of pulsewidth distortion. The code of 1111 corresponds to a balanced state for differential output. The pulse-width distortion is bidirectional around the balanced state (see the Typical Operating Characteristics section). Programming CML Output Settings Amplitude of the CML output stage is controlled by an 8-bit DAC register (SET_CML). The differential output amplitude is up to 1000mVP-P with 4.6mVP-P resolution (assuming an ideal 100 differential load). The guaranteed output CML DAC range is up to 215. Output Voltage ROUT (mVP-P) = 40 + 4.55 (SET_CML) Select the Coupling Capacitor For AC-coupling, the coupling capacitors C IN and COUT should be selected to minimize the receiver's deterministic jitter. Jitter is decreased as the input lowfrequency cutoff (fIN) is decreased. fIN = 1/[2(50)(CIN)] The recommended C IN and C OUT is 0.1F for the MAX3799. Select the Offset-Correction Capacitor The capacitor between CAZ1 and CAZ2 determines the time constant of the signal path DC-offset cancellation loop. To maintain stability, it is important to keep at 28 least a one-decade separation between fIN and the low-frequency cutoff (fOC) associated with the DC-offset cancellation circuit. A 1nF capacitor between CAZ1 and CAZ2 is recommended for the MAX3799. Applications Information Layout Considerations To minimize inductance, keep the connections between the MAX3799 output pins and laser diode as close as possible. Optimize the laser diode performance by placing a bypass capacitor as close as possible to the laser anode. Use good high-frequency layout techniques and multiple-layer boards with uninterrupted ground planes to minimize EMI and crosstalk. Exposed-Pad Package The exposed pad on the 32-pin TQFN provides a very low-thermal resistance path for heat removal from the IC. The pad is also electrical ground on the MAX3799 and must be soldered to the circuit board ground for proper thermal and electrical performance. Refer to Application Note 862: HFAN-08.1: Thermal Considerations of QFN and Other Exposed-Paddle Packages for additional information. Laser Safety and IEC 825 Using the MAX3799 laser driver alone does not ensure that a transmitter design is compliant with IEC 825. The entire transmitter circuit and component selections must be considered. Each user must determine the level of fault tolerance required by the application, recognizing that Maxim products are neither designed nor authorized for use as components in systems intended for surgical implant into the body, for applications intended to support or sustain life, or for any other application in which the failure of a Maxim product could create a situation where personal injury or death could occur. Table 6. Eye-Crossing Settings for SET_PWCTRL SET_PWCTRL[3:0] PWD SET_PWCTRL[3:0] PWD 1000 -7 0111 8 1001 -6 0110 7 1010 -5 0101 6 1011 -4 0100 5 1100 -3 0011 4 1101 -2 0010 3 1110 -1 0001 2 1111 0 0000 1 ______________________________________________________________________________________ 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver REGISTER FUNCTION/ ADDRESS REGISTER NAME NORMAL MODE SETUP MODE BIT NUMBER /TYPE BIT NAME DEFAULT VALUE NOTES Receiver Control Register 1 Address = H0x00 RXCTRL1 R RW 1 RATE_SEL 0 Mode-select 0: high-gain mode, 1: highbandwidth mode R RW 6 LOS_EN 1 LOS control 0: disable, 1: enable (always 0 when RX_EN = 0) R RW 5 LOS_POL 1 LOS polarity 0: inverse, 1: normal R RW 4 RX_POL 1 Rx polarity 0: inverse, 1: normal R RW 3 SQ_EN 0 Squelch 0: disable, 1: enable R RW 2 RX_EN 1 Rx control 0: disable, 1: enable R RW 1 RXDE_EN 0 Rx deemphasis 0: disable, 1: enable R RW 0 AZ_EN 1 Rx autozero control 0: disable, 1: enable (always 0 when RX_EN = 0) R R 0 (sticky) LOS X Copy of LOS output signal MSB output level DAC Receiver Control Register 2 Address = H0x01 Receiver Status Register Address = H0x02 Output CML Level Setting Register Address = H0x03 LOS Threshold Level Setting Register Address = H0x04 RXCTRL2 RXSTAT SET_CML SET_LOS R RW 7 SET_CML[7] 0 R RW 6 SET_CML[6] 1 R RW 5 SET_CML[5] 0 R RW 4 SET_CML[4] 1 R RW 3 SET_CML[3] 0 R RW 2 SET_CML[2] 0 R RW 1 SET_CML[1] 1 R RW 0 SET_CML[0] 1 LSB output level DAC R RW 5 SET_LOS[5] 0 MSB LOS threshold DAC R RW 4 SET_LOS[4] 0 R RW 3 SET_LOS[3] 1 R RW 2 SET_LOS[2] 1 R RW 1 SET_LOS[1] 0 R RW 0 SET_LOS[0] 0 LSB LOS threshold DAC ______________________________________________________________________________________ 29 MAX3799 Table 7. Register Summary MAX3799 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver Table 7. Register Summary (continued) REGISTER FUNCTION/ ADDRESS Transmitter Control Register Address = H0x05 Transmitter Status Register 1 Address = H0x06 Transmitter Status Register 2 Address = H0x07 Bias Current Setting Register Address = H0x08 REGISTER NAME TXCTRL TXSTAT1 TXSTAT2 SET_IBIAS NORMAL MODE SETUP MODE BIT NUMBER /TYPE BIT NAME DEFAULT VALUE R RW 3 TXDE_EN 0 R RW 2 SOFTRES 0 Global digital reset Tx deemphasis 0: disable, 1: enable R RW 1 TX_POL 1 Tx polarity 0: inverse, 1: normal R RW 0 TX_EN 1 Tx control 0: disable, 1: enable R R 7 (sticky) FST[7] X TX_POR TX_VCC lowlimit violation R R 6 (sticky) FST[6] X BMON open/shorted to VCC R R 5 (sticky) X X R R 4 (sticky) X X R R 3 (sticky) FST3] X VTOUT+/- common-mode low-limit violation R R 2 (sticky) FST[2] X VTOUT+/- low-limit violation R R 1 (sticky) FST[1] X BIAS open or shorted to GND R R 0 (sticky) TX_FAULT X Copy of FAULT signal in case POR bits 6 to 1 reset to 0 R R 3 (sticky) IMODERR X Warning increment result > IMODMAX R R 2 (sticky) IBIASERR X Warning increment result > IBIASMAX R R 1 (sticky) TXED X Tx edge detection R R 0 (sticky) Unused X Unused R RW 8 SET_IBIAS[8] 0 MSB bias DAC R RW 7 SET_IBIAS[7] 0 R RW 6 SET_IBIAS[6] 0 R RW 5 SET_IBIAS[5] 0 R RW 4 SET_IBIAS[4] 0 R RW 3 SET_IBIAS[3] 1 R RW 2 SET_IBIAS[2] 0 R RW 1 SET_IBIAS[1] 0 0 SET_IBIAS[0] 0 Accessible through REG_ADDR = 13 30 NOTES LSB bias DAC ______________________________________________________________________________________ 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver REGISTER FUNCTION/ ADDRESS Modulation Current Setting Register Address = H0x09 REGISTER NAME SET_IMOD NORMAL MODE SETUP MODE BIT NUMBER /TYPE BIT NAME DEFAULT VALUE R RW 8 SET_IMOD[8] 0 R RW 7 SET_IMOD[7] 0 R RW 6 SET_IMOD[6] 0 R RW 5 SET_IMOD[5] 1 R RW 4 SET_IMOD[4] 0 R RW 3 SET_IMOD[3] 0 R RW 2 SET_IMOD[2] 1 R RW 1 SET_IMOD[1] 0 0 SET_IMOD[0] 0 LSB modulation DAC MSB modulation limit Accessible through REG_ADDR = 12 Maximum Modulation Current Setting Register Address = H0x0A Maximum Bias Current Setting Register Address = H0x0B Modulation Current Increment Setting Register Address = H0x0C IMODMAX IBIASMAX MODINC R RW 7 IMODMAX[7] 0 R RW 6 IMODMAX[6] 0 R RW 5 IMODMAX[5] 1 R RW 4 IMODMAX[4] 1 R RW 3 IMODMAX[3] 0 R RW 2 IMODMAX[2] 0 R RW 1 IMODMAX[1] 0 MAX3799 Table 7. Register Summary (continued) NOTES MSB modulation DAC R RW 0 IMODMAX[0] 0 LSB modulation limit R RW 7 IBIASMAX[7] 0 MSB bias limit R RW 6 IBIASMAX[6] 0 R RW 5 IBIASMAX[5] 0 R RW 4 IBIASMAX[4] 1 R RW 3 IBIASMAX[3] 0 R RW 2 IBIASMAX[2] 0 R RW 1 IBIASMAX[1] 1 R RW 0 IBIASMAX[0] 0 LSB bias limit R R 7 SET_IMOD[0] 0 LSB of SET_IMOD DAC register address = H0x09 R R 6 X 0 R R 5 DE_INC 0 Deemphasis increment 0: no update, 1: SET_TXDE updates 1 LSB RW RW 4 MODINC[4] 0 MSB MOD DAC two's complement RW RW 3 MODINC[3] 0 RW RW 2 MODINC[2] 0 RW RW 1 MODINC[1] 0 RW RW 0 MODINC[0] 0 LSB MOD DAC two's complement ______________________________________________________________________________________ 31 MAX3799 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver Table 7. Register Summary (continued) REGISTER FUNCTION/ ADDRESS Bias Current Increment Setting Register Address = H0x0D Mode Control Register Address = H0x0E Transmitter PulseWidth Control Register Address = H0x0F Transmitter Deemphasis Control Register Address = H0x10 32 REGISTER NAME BIASINC MODECTRL SET_ PWCTRL SET_TXDE NORMAL MODE SETUP MODE BIT NUMBER /TYPE BIT NAME DEFAULT VALUE R R 7 SET_IBIAS[0] 0 R R 6 X 0 R R 5 X 0 RW RW 4 BIASINC[4] 0 RW RW 3 BIASINC[3] 0 RW RW 2 BIASINC[2] 0 RW RW 1 BIASINC[1] 0 RW RW 0 BIASINC[0] 0 LSB bias DAC two's complement MSB mode control NOTES LSB of SET_IBIAS DAC register address = H0x08 MSB bias DAC two's complement RW RW 7 MODECTRL[7] 0 RW RW 6 MODECTRL[6] 0 RW RW 5 MODECTRL[5] 0 RW RW 4 MODECTRL[4] 0 RW RW 3 MODECTRL[3] 0 RW RW 2 MODECTRL[2] 0 RW RW 1 MODECTRL[1] 0 RW RW 0 MODECTRL[0] 0 LSB mode control MSB Tx pulse-width control R RW 3 SET_PWCTRL[3] 0 R RW 2 SET_PWCTRL[2] 0 R RW 1 SET_PWCTRL[1] 0 R RW 0 SET_PWCTRL[0] 0 LSB Tx pulse-width control R RW 3 SET_TXDE[3] 0 MSB Tx deemphasis R RW 2 SET_TXDE[2] 0 R RW 1 SET_TXDE[1] 0 R RW 0 SET_TXDE[0] 0 LSB Tx deemphasis ______________________________________________________________________________________ 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver MAX3799 VCCR VCCR DEEMPHASIS CONTROL 50 50 ROUT+ RIN+ ROUT50 CONTROL LOOP 50 RIN- VEER VEER VCCT VCCT DEEMPHASIS CONTROL 50 50 TOUT+ TIN+ TOUT50 CONTROL LOOP 50 TIN- VCCT VCCD VEET VEET 8k 75k SDA DISABLE VEET VCCR VCCD VEER FAULT, LOS 376 CLAMP RSEL SCL, CSEL 75k 75k VEET VEER VEER Figure 5. Simplified I/O Structures ______________________________________________________________________________________ 33 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver MAX3799 Typical Application Circuit SFP CONNECTOR SFP OPTICAL TRANSCEIVER +3.3V SUPPLY FILTER HOST BOARD HOST FILTER VCC_RX +3.3V 1nF CAZ2 CAZ1 VEER RIN+ VCCR 4.7 0.1F LOS 0.1F RINIMON ROUT+ 0.1F RECEIVER ROUT0.1F 10G PIN FLEX ROSA +3.3V RMON RSEL +3.3V VCCD SCL SDA CSEL 3-WIRE INTERFACE SerDes 10G VCSEL FLEX TOSA ZDIFF = 100 VCCT BIAS MAX3799 0.1F VSEL 0.1F TOUT- TIN+ 0.1F TOUT+ MD TRANSMITTER TIN0.1F ZDIFF = 100 DISABLE EP BMON VEET FAULT +3.3V 4.7 IMON 3-WIRE INTERFACE ADC TX_FAULT SFP+ CONTROLLER I2C MODE_DEF2 (SD) MODE_DEF1 (SCLK) TX_DISABLE RPD 2k VCC_TX SUPPLY FILTER 34 HOST FILTER ______________________________________________________________________________________ 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver Pad Configuration VEER 26 15 VCCT VCCR 27 14 TIN- RIN- 28 13 TIN+ 12 VCCT 11 CSEL 10 SDA 9 SCL MAX3799 RIN+ 29 VCCR 30 CAZ2 31 *EP + 7 VCCD 6 VCCR 5 ROUT- 4 ROUT+ 3 VCCR LOS 2 RSEL 1 VEER VEER TOUTVCCT VEET VCCT TOUT+ VCCT TINTIN+ VCCT GND GND RIN- CAZ2 CAZ1 PIN 1 CSEL SDA SCL GND DIE MAP 2800 m x 2550m (110.24mils x 100.39mils) *THE EXPOSED PAD MUST BE CONNECTED TO GROUND. Package Information Chip Information PROCESS: SiGe BiPOLAR VCCT RIN+ VCCR VCCR 8 THIN QFN (5mm x 5mm) BMON GND VCCR VCCR DISABLE CAZ1 32 VCCT GND BMON VCCD DISABLE 16 ROUTVCCR 17 BIAS BIAS 18 VCCR ROUT+ VCCT VEET 19 GND GND TOUT- 20 VCCT FAULT TOUT+ 21 RSEL VCCT 22 GND BIAS 23 DIE ID FAULT 24 VCCT 25 LOS VCCT NOT DRAWN TO SCALE TOP VIEW For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO. 32 TQFN-EP T3255+5 21-0140 90-0001 ______________________________________________________________________________________ 35 MAX3799 Pin Configuration MAX3799 1Gbps to 14Gbps, SFP+ Multirate Limiting Amplifier and VCSEL Driver Revision History REVISION NUMBER REVISION DATE 0 8/09 Initial release 1 6/10 Added the dice package and pad configuration to the Ordering Information and Pad Configuration sections DESCRIPTION PAGES CHANGED -- 1, 35 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. 36 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2010 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.