19-3467; Rev 0; 10/04 1Gbps to 4.25Gbps Multirate Transimpedance Amplifier with Photocurrent Monitor Features The MAX3793 transimpedance amplifier provides a compact low-power solution for applications from 1Gbps up to 4.25Gbps. The MAX3793 features 195nA input-referred noise, 3.5kΩ transimpedance gain, 2.9GHz bandwidth (CIN = 0.3pF) and 2.8mAP-P input overload. Operating from a +3.3V supply, the MAX3793 consumes only 106mW. An integrated filter resistor provides positive bias for the photodiode. These features, combined with a small die size, allow easy assembly into a TO-46 header with a photodiode. The MAX3793 also includes an average photocurrent monitor. ♦ 4.7psP-P Deterministic Jitter (DJ) ♦ 195nARMS Input-Referred Noise ♦ 2.9GHz Small-Signal Bandwidth ♦ 2.8mAP-P AC Overload ♦ Photocurrent Output Monitor ♦ 3.5kΩ Differential Gain ♦ Compact Die Size (30 mils x 50 mils) The MAX3793 has a typical optical sensitivity of -20dBm (0.55A/W) at 4.25Gbps. Typical optical overload is at 4dBm. The MAX3793 and the MAX3794 limiting amplifiers provide a complete solution for multirate receiver applications. Ordering Information Applications SFF/SFP Transceiver Modules from 1Gbps to 4.25Gbps PART TEMP RANGE PIN-PACKAGE MAX3793E/D -40°C to +85°C Dice* *Dice are designed to operate from -40°C to +85°C ambient temperature, but are tested and guaranteed only at TA = +25°C. Gigabit Ethernet Optical Receivers Multirate Fibre-Channel Optical Receivers Typical Application Circuit HOST BOARD SFP OPTICAL RECEIVER CVCC CFILT RATE_SELECT FILT BWSEL MAX3793 MAX3794* 0.1µF OUT- 0.1µF OUT- IN- MON GND 0.1µF OUT+ IN+ OUT+ IN VCC 0.1µF VCC DISABLE RMON LOS VCC 4.7kΩ TO 10kΩ MOD-DEF1 DS1856/ DS1859 MOD-DEF2 *FUTURE PRODUCT ________________________________________________________________ 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 MAX3793 General Description MAX3793 1Gbps to 4.25Gbps Multirate Transimpedance Amplifier with Photocurrent Monitor ABSOLUTE MAXIMUM RATINGS Power-Supply Voltage (VCC) .................................-0.5V to +4.5V Continuous CML Output Current (OUT+, OUT-) ...............................................-25mA to +25mA Continuous Input Current (IN)...............................-4mA to +4mA Continuous Input Current (FILTER).......................-8mA to +8mA Operating Junction Temperature Range (TJ) ....-55°C to +150°C Storage Ambient Temperature Range (TSTG) ...-55°C to +150°C Die Attach Temperature...................................................+400°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. ELECTRICAL CHARACTERISTICS (VCC = +2.97V to +3.63V, TA = -40°C to +85°C. Typical values are at VCC = +3.3V, source capacitance CIN = 0.60pF, TA = +25°C, unless otherwise noted.) (Notes 1, 2) PARAMETER Power-Supply Current SYMBOL CONDITIONS MIN ICC Measured with AC-coupled output IOL (Note 3) TYP MAX UNITS 32 46 mA Input Bias Voltage Input Overload 1.0 BER = 10-12 , K28.5, at 1.0625Gbps Optical Input Sensitivity (850nm, re = 10dB, Responsiveness = 0.55A/W) BER = Input-Referred Noise (Notes 3, 4) Differential Transimpedance Small-Signal Bandwidth 2.2 10-12 , -23.5 K28.5, at 2.125Gbps -23 BW = 933MHz, 4th-order Bessel filter 195 264 BW = 2000MHz, 4th-order Bessel filter 377 420 Unfiltered output 449 615 3.5 4.5 2.8 -3dB, CIN = 0.6pF (Note 3) 1.9 2.5 3.2 -3dB, CIN = 0.3pF (Note 5) 2.36 2.9 3.56 (Note 3) Low-Frequency Cut-Off -3dB, IIN = 20µAAVE (Note 3) 0 20µAP-P < IIN < 100µAP-P, K28.5, at 4.25Gbps DJ 100µAP-P < IIN < 2.2mAP-P, K28.5, at 4.25Gbps TA = +100°C RFILT Differential Output Resistance ROUT Maximum Differential Output Voltage Output Edge Transition Time 2 VOD(MAX) Outputs terminated by 50Ω to VCC, IIN > 100µAP-P Outputs terminated by 50Ω to VCC 20% to 80%, IIN > 200µAP-P (Note 3) kΩ GHz kHz 4.7 11 6 16 10 27 psP-P 10 TA = +100°C, 100µAP-P < IIN < 2.2mAP-P, K28.5, at 4.25Gbps Photodiode Resistor nARMS dB 70 IIN = 20µAP-P, K28.5, at 4.25Gbps Deterministic Jitter (Notes 3, 6) dBm -20 Gain Peaking V mAP-P BER = 10-12 , K28.5, at 4.25Gbps IIN = 20µAAVE BW 2.8 10 600 750 930 Ω 85 100 115 Ω 480 mVP-P 220 73 95 ps TA = +100°C 90 _______________________________________________________________________________________ 1Gbps to 4.25Gbps Multirate Transimpedance Amplifier with Photocurrent Monitor (VCC = +2.97V to +3.63V, TA = -40°C to +85°C. Typical values are at VCC = +3.3V, source capacitance CIN = 0.60pF, TA = +25°C, unless otherwise noted.) (Notes 1, 2) PARAMETER SYMBOL Differential Output Return Loss Single-Ended Output Return Loss Power-Supply Noise Rejection (Note 7) PSNR Minimum Photocurrent to be Detected IAVGMIN Maximum Photocurrent to be Detected IAVGMAX Maximum Photocurrent Monitor Output Offset Photocurrent Monitor Output Offset Temperature Dependency IMON (OFFSET) ∆IMON (OFFSET) Monitor Output Compliance Voltage VMON Photocurrent Monitor Gain AMON CONDITIONS MIN TYP Frequency ≤ 1GHz 18 1GHz < frequency ≤ 4GHz 9 Frequency ≤ 1GHz 14 1GHz < frequency ≤ 4GHz 11 IIN = 0, f < 1MHz 47 IIN = 0, 1MHz ≤ f < 10MHz 22 MAX dB dB dB 2 1 10 0.21 0 2µA ≤ IAVG ≤ 1.0mA Photocurrent Monitor Gain Stability 2µA ≤ IAVG ≤ 1.0mA (Notes 3, 8) Photocurrent Monitor Gain Bandwidth 2µA ≤ IAVG ≤ 1.0mA µA mA IIN = 0µAP-P IIN = 0µAP-P ∆IMON(OFFSET) = ABS (IMON(OFFSET) (-40°C) - IMON(OFFSET) (+100°C)) UNITS µA 2 1 -10 V A/A +10 7 µA % MHz Note 1: Die parameters are production tested at room temperature only, but are guaranteed by design and characterization from -40°C to +85°C. Note 2: Source capacitance represents the total external capacitance at the IN pad during characterization of the noise and bandwidth parameters. Note 3: Guaranteed by design and characterization. Note 4: Input-referred noise is: RMS Output Noise Gain at f = 100MHz Note 5: Values are derived by calculation from the CIN = 0.6pF measurements. Note 6: DJ is the sum of pulse-width distortion (PWD) and pattern-dependent jitter (PDJ). DJ is measured using a 3.2GHz 4th-order Bessel filter on the input. Note 7: Power-supply noise rejection PSNR = -20log(∆VOUT / ∆VCC), where ∆VOUT is the change in differential output voltage and ∆VCC is the noise on VCC. Note 8: Gain stability is defined as (AMON - AMON-NOM) / (AMON-NOM) over the listed current range, temperature, and supply variation. Nominal gain is measured at VCC = +3.3V and +25°C. _______________________________________________________________________________________ 3 MAX3793 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VCC = +3.3V, CIN = 0.6pF, TA = +25°C, unless otherwise noted.) 70 GAIN (dBΩ) UNFILTERED 400 300 65 60 BW = 2.0GHz 55 200 18 DETERMINISTIC JITTER (psP-P) 500 MAX3793 toc02 75 MAX3793 toc01 600 50 100 -20 0 20 40 60 12 9 6 0 10M 100 80 100M 1G 10G 20µ 400µ 800µ 1.2m 1.6m TEMPERATURE (°C) FREQUENCY (Hz) INPUT AMPLITUDE (AP-P) SMALL-SIGNAL TRANSIMPEDANCE vs. TEMPERATURE DIFFERENTIAL S22 vs. FREQUENCY SUPPLY CURRENT vs. TEMPERATURE -5 -10 -15 S22 (dB) 70 -20 -25 -30 65 70 -35 2.0m MAX3793 toc06 0 MAX3793 toc04 75 60 SUPPLY CURRENT (mA) -40 DATA RATE = 4.25Gbps K28.5 PATTERN, UNFILTERED INPUT 15 3 MAX3793 toc05 INPUT-REFERRED NOISE (nARMS) DETERMINISTIC JITTER vs. INPUT AMPLITUDE FREQUENCY RESPONSE MAx3793 toc03 INPUT-REFERRED NOISE vs. TEMPERATURE TRANSIMPEDANCE (dBΩ) 50 40 30 20 -40 10 -45 60 0 -50 -40 -20 0 20 40 60 80 100 10M 100M TEMPERATURE (°C) -40 10G 1G -20 0 0.6 0.4 MAX3793 toc08 200 150 OUTPUT VOLTAGE (mV) 0.8 40 DC TRANSFER FUNCTION (VFILT = 0V) MAX3793 toc07 1.0 20 100 50 0 -50 -100 0.2 -150 -200 0 0 0.2 0.4 0.6 0.8 AVERAGE INPUT CURRENT (mA) 4 1.0 60 TEMPERATURE (°C) FREQUENCY (Hz) MONITOR OUTPUT CURRENT vs. AVERAGE INPUT CURRENT MONITOR OUTPUT CURRENT (mA) MAX3793 1Gbps to 4.25Gbps Multirate Transimpedance Amplifier with Photocurrent Monitor -100 -50 0 50 INPUT CURRENT (µA) _______________________________________________________________________________________ 100 80 100 1Gbps to 4.25Gbps Multirate Transimpedance Amplifier with Photocurrent Monitor EYE DIAGRAM INPUT = 20µAP-P, DATA RATE = 1.0625Gbps MAX3793 toc09 EYE DIAGRAM INPUT = 20µAP-P, DATA RATE = 2.125Gbps MAX3793 toc10 K28.5 PATTERN 10mV/div EYE DIAGRAM INPUT = 20µAP-P, DATA RATE = 4.25Gbps MAX3793 toc11 K28.5 PATTERN 10mV/div K28.5 PATTERN 10mV/div 200ps/div 100ps/div 48ps/div EYE DIAGRAM INPUT = 2.2mAP-P, DATA RATE = 4.25Gbps EYE DIAGRAM TA = +100°C INPUT = 20µAP-P, DATA RATE = 4.25Gbps PHOTOCURRENT MONITOR OFFSET TEMPERATURE DEPENDENCY HISTOGRAM MAX3793 toc13 45 K28.5 PATTERN MAX3793 toc14 MAX3793 toc12 K28.5 PATTERN 40 40mV/div % OF UNITS 35 10mV/div 30 25 20 15 10 5 0 48ps/div 48ps/div 0.28-0.42 0.56-0.7 0.14-0.28 0.7-0.84 0.42-0.56 IMON CHANGE OVER TEMPERATURE (µA) 0-0.14 _______________________________________________________________________________________ 5 MAX3793 Typical Operating Characteristics (continued) (VCC = +3.3V, CIN = 0.6pF, TA = +25°C, unless otherwise noted.) MAX3793 1Gbps to 4.25Gbps Multirate Transimpedance Amplifier with Photocurrent Monitor Pin Description BOND PAD NAME 1 OUT+ FUNCTION 2, 3 VCC +3.3V Supply Voltage. The pads are not internally connected. Therefore, they must always be externally bonded. 4 FILT Provides bias voltage for the photodiode through a 750Ω resistor to VCC. When grounded, this pin disables the DC-cancellation amplifier to allow a DC path from IN to OUT+ and OUT- for testing. 5 IN 6 MON Photocurrent Monitor. Output current from MON is proportional to the average current in RFILT. Connect a resistor between MON and ground to monitor the average photocurrent. 7, 11 GND Circuit Ground. The pads are not internally connected. Therefore, they must always be externally bonded. 8, 10 N.C. No Connection 9 OUT- Inverting Data Output. Current flowing into IN causes the voltage at OUT- to decrease. Noninverting Data Output. Current flowing into IN causes the voltage at OUT+ to increase. TIA Input. Signal current from photodiode flows into this pin. See the Wire Bonding section for recommended bonding sequence, Figure 4. Functional Diagram VCC Rf VOLTAGE AMPLIFIER OUTPUT ROUT BUFFER ROUT OUT+ IN TIA OUT- LOWPASS FILTER EN MAX3793 DC CANCELLATION VCC FILT MON 6 FILTER NETWORK _______________________________________________________________________________________ 1Gbps to 4.25Gbps Multirate Transimpedance Amplifier with Photocurrent Monitor AMPLITUDE MAX3793 AMPLITUDE INPUT FROM PHOTODIODE TIME TIME OUTPUT (SMALL SIGNALS) INPUT AFTER DC CANCELLATION OUTPUT (LARGE SIGNALS) Figure 1. MAX3793 Limited Output Figure 2. DC-Cancellation Effect on Input Detailed Description The MAX3793 transimpedance amplifier is designed for 1Gbps to 4.25Gbps fiber optic applications. The MAX3793 is comprised of a transimpedance amplifier, a voltage amplifier, an output buffer, a DC-cancellation circuit, a photodiode biasing resistor, and a photocurrent monitor (see the Functional Diagram). Transimpedance Amplifier The signal current at the input flows into the summing node of a high-gain amplifier. Shunt feedback through resistor RF converts this current into a voltage. Schottky diodes clamp the output signal for large input currents (Figure 1). Voltage Amplifier The voltage amplifier provides additional gain and converts the transimpedance amplifier single-ended output signal into a differential signal. Output Buffer The output buffer is designed to drive a 100Ω differential load between OUT+ and OUT-. For optimum supply noise rejection, the MAX3793 should be terminated with a matched load. The MAX3793 outputs do not drive a DC-coupled grounded load. The outputs should always be AC-coupled. Refer to Application Note HFAN-1.1: Choosing AC-Coupling Capacitors for a more detailed discussion on selecting capacitors. If a single-ended output is required, both the used and the unused outputs should be terminated in a similar manner. See Figure 6. DC-Cancellation Circuit The DC-cancellation circuit uses low-frequency feedback to remove the DC component of the input signal (Figure 2). This feature centers the input signal within the transimpedance amplifier’s linear range, thereby reducing pulse-width distortion. The DC-cancellation circuit is internally compensated and does not require external capacitors. This circuit minimizes pulse-width distortion for data sequences that exhibit a 50% mark density. A mark density significantly different from 50% causes the MAX3793 to generate pulse-width distortion. Grounding the FILT pin disables the DC-cancellation circuit. For normal operation, the DC-cancellation circuit must be enabled. Photocurrent Monitor The MAX3793 includes an average photocurrent monitor. The current sourced from MON to ground is proportionally equal to the average R FILT current (see the Typical Operating Characteristics). This RFILT is used to bias the photodiode, see Figure 7. RFILT is an internal 750Ω resistor between V CC and FILT. This resistor is to be used in conjunction with an external C FILT to bias the photodiode. The current through this resistor is monitored and creates the photocurrent monitor output. For test purposes, driving FILT below 0.5V disables the DC-cancellation circuit. Design Procedure Select Photodiode Noise performance and bandwidth are adversely affected by capacitance on the TIA input node. Select a low-capacitance photodiode to minimize the total input capacitance on this pin. The MAX3793 is optimized for 0.6pF of capacitance on the input. Select CFILT The filter resistor of the MAX3793, combined with an external capacitor, can be used to reduce noise (see the Typical Application Circuit). Current generated by supply noise voltage is divided between CFILT and CIN. Assuming the filter capacitor is much larger than the photodiode capacitance, the input noise current due to supply noise is: INOISE = (VNOISE x CIN) / (RFILT x CFILT) _______________________________________________________________________________________ 7 MAX3793 1Gbps to 4.25Gbps Multirate Transimpedance Amplifier with Photocurrent Monitor If the amount of tolerable noise is known, the filter capacitor can be easily selected: CFILT = (VNOISE x CIN) / (RFILT x INOISE) For example, with maximum noise voltage = 100mVP-P, CIN = 0.6pF, RFILT = 750Ω, and INOISE at 350nA, the filter capacitor is: CFILT = (100mV x 0.6pF) / (750Ω x 350nA) = 229pF Select RMON If photocurrent monitoring is desired, connect a resistor between MON and ground to monitor the average photocurrent. Select the largest RMON possible: VCC MON PHOTODIODE CFILT 5-PIN HEADER CVCC FILT IN MON OUT- MAX3793 RMON = 2.0V IMONMAX where, IMONMAX is the largest average input current observed. An ammeter can also be used to monitor the current out of the MON pin. Layout Considerations Figure 3 shows suggested layouts for 4-pin and 5-pin TO headers. Wire Bonding For high-current density and reliable operation, the MAX3793 uses gold metalization. For best results, use gold-wire ball-bonding techniques. Exercise caution if attempting wedge bonding. The die size is 30 mils x 50 mils (0.762mm x 1.27mm), and the die thickness is 15 mils (380µm). Bond-pad size for the VCC, GND, OUT+, and OUT- pads is 94µm x 94µm. Bond-pad size for the FILT, IN, and MON pads is 79µm x 79µm; all bond-pad metal thickness is 1.2µm. Refer to Maxim Application Note HFAN-08.0.1: Understanding Bonding Coordinates and Physical Die Size for additional information on bondpad coordinates. Recommended bonding sequence is shown in Figure 4. OUT+ PHOTODIODE IS MOUNTED ON CFILT, CASE IS GROUND. 11 7 CFILT 1 VCC 4-PIN HEADER 3 CVCC FILT IN MON OUT- OUT+ CVCC 10 PHOTODIODE CFILT 5 2 6 8 9 4 MAX3793 Figure 3. Suggested TO Header Layouts 8 PHOTODIODE IS MOUNTED ON CFILT, CASE IS GROUND. MAX3793 Figure 4. Recommended MAX3793 Bonding Scheme _______________________________________________________________________________________ 1Gbps to 4.25Gbps Multirate Transimpedance Amplifier with Photocurrent Monitor Optical Power Relations Many of the MAX3793 specifications relate to the input signal amplitude. When working with optical receivers, the input is sometimes expressed in terms of average optical power and extinction ratio. Figure 5 and Table 1 show relations that are helpful for converting optical power to input signal when designing with the MAX3793. To obtain a system bit-error rate (BER) of 1E-12, the signal-to-noise ratio must always exceed 14:1. The input sensitivity, expressed in average power, can be estimated as: 14.1 × IN (re + 1) Sensitivity = 10 log × 1000 dBm 2 × ρ × (re − 1)) where, ρ is the photodiode responsivity in A/W, and IN is the RMS noise current in amps. Optical Sensitivity Calculation The input-referred RMS noise current (I N ) of the MAX3793 generally determines the receiver sensitivity. I Overload = 10log OL × 1000 dBm 2 × ρ PI OPTICAL POWER Input Optical Overload Overload is the largest input that the MAX3793 accepts while meeting DJ specifications. Optical overload can be estimated in terms of average power with the following equation: Optical Linear Range PAVG The MAX3793 has high gain, which limits the output when the input signal exceeds 50µAP-P. The MAX3793 operates in a linear range for inputs not exceeding: PO 50µA × (re + 1) Linear Range = 10 log × 1000 dBm 2 × ρ × (re − 1) TIME Figure 5. Optical Power Relations Table 1. Optical Power Relations* SYMBOL RELATION Average power PARAMETER PAVG PAVG = (P0 + P1) / 2 Extinction ratio re re = P1 / P0 Optical power of a 1 P1 P1 = 2PAVG Optical power of a 0 P0 P0 = 2PAVG / (re + 1) Optical modulation amplitude PIN PIN = P1 − P0 = 2PAVG re − re re + 1 re + *Assuming a 50% average mark density. _______________________________________________________________________________________ 9 MAX3793 Applications Information MAX3793 1Gbps to 4.25Gbps Multirate Transimpedance Amplifier with Photocurrent Monitor Interface Schematics VCC VCC VCC 50Ω VCC 50Ω OUT+ RFILT 750Ω 750Ω FILT VCC OUTVCC MON Figure 6. Equivalent Output Figure 7. FILT and MON Interface Table 2. Bond-Pad Coordinates Pad Coordinates COORDINATES (µm) PAD NAME X Y BP1 OUT+ 40.2 650.6 BP2 VCC 40.2 391.6 47.2 BP3 VCC 47.2 BP4 FILT 166.2 40.2 BP5 IN 278.2 40.2 BP6 MON 390.2 40.2 BP7 GND 509.2 47.2 BP8 N.C. 516.2 289.2 BP9 OUT- 509.2 650.6 BP10 N.C. 393.0 1032.8 BP11 GND 274.0 1025.8 10 Table 2 gives center pad coordinates for the MAX3793 bondpads. See Application Note HFAN-8.0.1: Understanding Bonding Coordinates and Physical Die Size for more information on bondpad coordinates. Chip Information TRANSISTOR COUNT: 475 PROCESS: SiGe Bipolar Package Information For the latest package outline information, go to www.maxim-ic.com/packages. ______________________________________________________________________________________ 1Gbps to 4.25Gbps Multirate Transimpedance Amplifier with Photocurrent Monitor N.C. 11 10 HD682-A MAX3793 OUT+ 1 VCC 2 VCC GND 3 4 5 6 FILT IN MON 9 OUT- 8 N.C. 7 GND 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 ____________________ 11 © 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX3793 Pin Configuration/Chip Topography