19-2207; Rev 1; 3/05 Low-Noise, Fibre Channel Transimpedance Amplifiers Features The MAX3275/MAX3277 transimpedance amplifiers provide a compact low-power solution for communication up to 2.125Gbps. They feature 300nA inputreferred noise at 2.1GHz bandwidth (BW) with 0.85pF input capacitance. The parts also have 2mA P-P AC input overload. ♦ Up to 2.125Gbps (NRZ) Data Rates The MAX3277 is identical to the MAX3275, but with the output polarities inverted for optimum packaging flexibility. Both parts operate from a single 3.3V supply and consume only 83mW. The MAX3275/MAX3277 are compact 24mil x 47mil die and require no external compensation capacitor. A space-saving filter connection is provided for positive bias to the photodiode through an on-chip 600Ω resistor to V CC. These features allow easy assembly into a TO-46 or TO-56 header with a photodiode. The MAX3275/MAX3277 and MAX3274 limiting amplifiers provide a two-chip solution for dual-rate, fibre channel receiver applications. ♦ 25mA Supply Current at +3.3V ♦ 7psP-P Deterministic Jitter for <100µAP-P Input Current ♦ 300nARMS Input-Referred Noise at 2.1GHz Bandwidth ♦ 2.3GHz Small-Signal Bandwidth ♦ 2.0mAP-P AC Overload ♦ Die Size: 24mil x 47mil Ordering Information PART TEMP RANGE PIN-PACKAGE MAX3275U/D 0°C to +85°C Dice* MAX3277U/D 0°C to +85°C Dice* *Dice are guaranteed to operate from 0°C to +85°C, but are tested only at TA = +25°C. Applications Dual-Rate Fibre Channel Optical Receivers Gigabit Ethernet Optical Receivers Typical Application Circuit SMALL FORM FACTOR OPTICAL RECEIVER HOST SERVER OR SWITCH +3.3V +3.3V 4.7kΩ TO 10kΩ 400pF 600Ω VCC LOS LOS MAX3275 OUT+ CFILTER 400pF IN MAX3274 0.1µF 0.1µF OUT+ IN+ 100Ω TIA OUT- IN- LIMITING AMP 100Ω OUT- 0.1µF GND 0.1µF TH SQUELCH 660Ω DESERIALIZER BWSEL RATE SELECT ________________________________________________________________ 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 MAX3275/MAX3277 General Description MAX3275/MAX3277 Low-Noise, Fibre Channel Transimpedance Amplifiers ABSOLUTE MAXIMUM RATINGS Power-Supply Voltage (VCC) .................................-0.5V to +4.0V 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 = +3.0V to +3.6V, TA = 0°C to +85°C. Typical values are at VCC = +3.3V, source capacitance (CIN) = 0.85pF, TA = +25°C, unless otherwise noted.) (Notes 1, 2) PARAMETER Supply Current Small-Signal Bandwidth SYMBOL ICC BW Low-Frequency Cutoff CONDITIONS MIN TYP -3dB, CIN = 0.6pF (Note 3) 2.0 -3dB, CIN = 0.85pF (Note 3) 1.7 2.3 2.7 Including output termination current -3dB, input current = 40µA (Note 3) MAX UNITS 25 41 mA 2.7 3.3 65 Input Bias Voltage Input-Referred Noise IN CIN = 0.6pF, BW = 0.8GHz (Notes 3, 4) 185 250 CIN = 0.6pF, BW = 1.6GHz (Notes 3, 4) 245 350 CIN = 0.6pF, BW = 2.1GHz (Notes 3, 4) 275 380 CIN = 0.85pF, BW = 0.8GHz (Notes 3, 4) 193 275 CIN = 0.85pF, BW = 1.6GHz (Notes 3, 4) 272 400 CIN = 0.85pF, BW = 2.1GHz (Notes 3, 4) 300 430 (Notes 3, 5) 2 DC Input Overload (Note 5) 1 Output Resistance (OUT+, OUT-) Deterministic Jitter DJ 2 mA P-P 690 Ω Single-ended 42.5 Ω 50 57.5 1mAP-P < input < 2mAP-P (Notes 3, 6, 7) 15 40 100µAP-P < input ≤ 1mAP-P (Notes 3, 6, 7) 15 31 Differential output 2.8 Transimpedance Linear Range 0.95 < linearity < 1.05 (Note 8) 50 Data Output Swing Input > 100µAP-P (Note 9) 220 Output Data-Transition Time PSR mAP-P 600 10µAP-P < input ≤ 100µAP-P (Notes 3, 6, 7) Power-Supply Rejection nARMS 510 Transimpedance Output Return Loss V Ω 40 AC Input Overload Filter Resistance kHz 1.0 Input Resistance GHz 7 16 3.3 3.8 psP-P kΩ µAP-P 300 500 mVP-P Input > 200µAP-P, 20% to 80% rise/fall time (Notes 3, 10) 90 140 ps Freq ≤ 1GHz 15 1GHz < freq ≤ 2GHz 10 f < 1MHz (Note 11) 40 1MHz ≤ f < 10MHz (Note 11) 34 _______________________________________________________________________________________ dB dB Low-Noise, Fibre Channel Transimpedance Amplifiers (VCC = +3.0V to +3.6V, TA = 0°C to +85°C. Typical values are at VCC = +3.3V, source capacitance (CIN) = 0.85pF, TA = +25°C, unless otherwise noted.) (Notes 1, 2) Note 1: Die parameters are production tested at room temperature only, but are guaranteed by design and characterization from 0°C to +85°C. Note 2: Source capacitance represents the total capacitance at the IN pad during characterization of the noise and bandwidth parameters. Note 3: Guaranteed by design and characterization. Note 4: Measured using an RF-power meter with no pattern applied at the input. The TIA output is bandwidth limited for measurement using a 4th-order Bessel Thompson filter. The -3dB frequency of the filter matches the frequency (0.8GHz, 1.6GHz, or 2.1GHz) for the specified noise BW. Note 5: DC offset and deterministic jitter may exceed specification if AC or DC overload conditions are exceeded. Note 6: Using fibre channel K28.5± pattern. The input bandwidth is limited to 0.75 ✕ (2.125Gbps) by a 4th-order Bessel Thompson filter. Measured differentially across an AC-coupled 100Ω external load. Note 7: K28.5± pattern: (00111110101100000101). Note 8: Gain may vary ±5% relative to reference measured with 30µAP-P input. Note 9: Production tested with 1mAP-P input. Note 10: Using a K28.7 (0011111000) pattern. Measured differentially across an AC-coupled 100Ω external load. Note 11: Power-supply rejection PSR = -20log(∆VOUT/∆VCC), where ∆VOUT is the differential output voltage and ∆VCC is the noise on VCC. Typical Operating Characteristics (VCC = +3.3V, CIN = 0.85pF, TA = +25°C, unless otherwise noted.) CIN = 0.6pF 220 210 CIN = 0.85pF 200 190 CIN = 0.6pF 180 20 40 60 80 AMBIENT TEMPERATURE (°C) 100 67 65 63 61 59 BW = 0.8GHz 150 0 69 170 160 BW = 1.6GHz MAX3275 toc03 230 71 TRANSIMPEDANCE (dBΩ) CIN = 0.85pF CIN IS SOURCE CAPACITANCE PRESENTED TO DIE, INCLUDING PIN DIODE, AND PARASITIC INTERCONNECT CAPACITANCE 240 FREQUENCY RESPONSE MAX3275 toc02 CIN IS SOURCE CAPACITANCE PRESENTED TO DIE, INCLUDING PIN DIODE, AND PARASITIC INTERCONNECT CAPACITANCE 250 INPUT-REFERRED NOISE (nARMS) 350 340 330 320 310 300 290 280 270 260 250 240 230 220 210 200 INPUT-REFERRED NOISE vs. TEMPERATURE MAX3275 toc01 INPUT-REFERRED NOISE (nARMS) INPUT-REFERRED NOISE vs. TEMPERATURE 57 0 20 40 60 80 AMBIENT TEMPERATURE (°C) 100 100M 1G 10G FREQUENCY (Hz) _______________________________________________________________________________________ 3 MAX3275/MAX3277 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (continued) (VCC = +3.3V, CIN = 0.85pF, TA = +25°C, unless otherwise noted.) DETERMINISTIC JITTER vs. INPUT AMPLITUDE 35 30 25 20 15 10 5 0 0.1 1 10 MAX3275 toc06 2.9 2.8 CIN = 0.6pF 2.7 2.6 2.5 2.4 2.3 CIN = 0.85pF 2.2 2.1 2.0 0 20 40 60 100 80 0 20 40 60 80 100 INPUT AMPLITUDE (mAP-P) AMBIENT TEMPERATURE (°C) AMBIENT TEMPERATURE (°C) EYE DIAGRAM (INPUT = 10µAP-P) EYE DIAGRAM (INPUT = 2mAP-P) DIFFERENTIAL OUTPUT REFLECTION COEFFICIENT MAX3275 toc09 0 MAX3275 toc08 MAX3275 toc07 0.01 BANDWIDTH vs. TEMPERATURE 3.0 BANDWIDTH (GHz) TRANSIMPEDANCE (dBΩ) 40 74 73 72 71 70 69 68 67 66 65 64 63 62 61 60 MAX3275 toc05 2.125Gbps K28.5 INPUT 45 MAX3275 toc04 SMALL-SIGNAL TRANSIMPEDANCE vs. TEMPERATURE 50 DETERMINISTIC JITTER (psP-P) -5 S22 (dB) -10 50mV/div 5mV/div -15 -20 -25 -30 -35 INPUT: K28.5 INPUT: K28.5 -40 0 80ps/div 80ps/div 500M 1G 1.5G 2G FREQUENCY (Hz) DC TRANSFER FUNCTION (FILTER = GND) SUPPLY CURRENT vs. TEMPERATURE 45 150 OUTPUT VOLTAGE (mV) 40 35 30 25 20 15 MAX3275 toc11 200 MAX3275 toc10 50 SUPPLY CURRENT (mA) MAX3275/MAX3277 Low-Noise, Fibre Channel Transimpedance Amplifiers 100 50 0 -50 -100 10 -150 5 -200 0 0 20 40 60 80 AMBIENT TEMPERATURE (°C) 4 100 -200 -100 0 100 200 INPUT CURRENT (µA) _______________________________________________________________________________________ 2.5G 3G Low-Noise, Fibre Channel Transimpedance Amplifiers MAX3275 BOND PAD MAX3277 BOND PAD NAME 1, 9 1, 9 VCC Supply Voltage 2, 5 2, 5 GND Circuit Ground 3 4 OUT- Inverting Data Output. Current flowing into IN causes the voltage at OUT- to decrease. 4 3 OUT+ Noninverting Data Output. Current flowing into IN causes the voltage at OUT+ to increase. 6 6 N.C. 7 7 FILTER 8 8 IN FUNCTION No Connection. Not internally connected. Provides bias voltage for the photodiode through a 600Ω 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. TIA Input. Signal current from photodiode flows into this pin. VCC Rf VOLTAGE AMPLIFIER IN OUTPUT BUFFER 50Ω 50Ω OUT+ OUT- TIA VCC VCC DC CANCELLATION 600Ω DISABLE FILTER GND LOWPASS FILTER MAX3275 MAX3277 Figure 1. Functional Diagram Detailed Description The MAX3275/MAX3277 are transimpedance amplifiers designed for up to 2.125Gbps fibre channel applications. A functional diagram of the MAX3275/MAX3277 is shown in Figure 1. The MAX3275/MAX3277 comprises a transimpedance amplifier stage, a voltage amplifier stage, an output buffer, and a direct-current feedback cancellation circuit. Transimpedance Amplifier Stage The signal current at the input flows into the summing node of a high-gain amplifier. Shunt feedback through the resistor RF converts this current to a voltage. In parallel with the feedback are two back-to-back Schottky diodes that clamp the output signal for large input currents as shown in Figure 2. Voltage Amplifier Stage The voltage amplifier stage provides gain and converts the single-ended input to differential outputs. _______________________________________________________________________________________ 5 MAX3275/MAX3277 Pad Description AMPLITUDE AMPLITUDE INPUT FROM PHOTODIODE TIME TIME OUTPUT (SMALL SIGNALS) INPUT (AFTER DC CANCELLATION) OUTPUT (LARGE SIGNALS) Figure 2. MAX3275/MAX3277 Limited Output Output Buffer The output buffer provides a reverse-terminated voltage output. The buffer is designed to drive a 100Ω differential load between OUT+ and OUT-. The output current is divided between internal 50Ω resistors and the external load resistor. For optimum supply-noise rejection, the MAX3275/ MAX3277 should be terminated with a differential load. If a single-ended output is required, the unused output should be terminated in a similar manner. The MAX3275/MAX3277 will not drive a DC-coupled, 50Ω grounded load; however, it will drive a compatible 50Ω CML input. DC Cancellation Circuit The direct-current (DC) cancellation circuit uses lowfrequency feedback to remove the DC component of the input signal (Figure 3). This feature centers the input signal within the transimpedance amplifier’s linear range, thereby reducing pulse-width distortion caused by large input signals. Pulse-width distortion in small signals will not be corrected. The DC cancellation circuit is internally compensated and therefore does not require external capacitors. This circuit minimizes pulse-width distortion for data sequences that exhibit a 50% mark density and 8b/10b coding. A mark density significantly different from 50% will cause the MAX3275/MAX3277 to generate pulsewidth distortion. DC cancellation current is drawn from the input and creates noise. For low-level signals with little or no DC component, the added noise is insignificant. Applications Information Figure 3. DC Cancellation Effect on Input average optical power and extinction ratio. Figure 4 and Table 1 show relations that are helpful for converting optical power to input signal when designing with the MAX3275/MAX3277. (Refer to Application note HFAN–3.0.0 Accurately Estimating Optical Receiver Sensitivity.) Table 1. Optical Power Relations PARAMETER SYMBOL Average Power PAVG RELATION PAVG = (P0 + P1)/2 Extinction Ratio re re = P1/P0 Optical Power of a 1 P1 P1 = 2PAVG(re)/(re + 1) Optical Power of a 0 P0 P0 = 2PAVG/(re + 1) Signal Amplitude PIN PIN = P1 - P0 PIN = 2PAVG(re - 1)/(re + 1) P1 OPTICAL POWER MAX3275/MAX3277 Low-Noise, Fibre Channel Transimpedance Amplifiers PAVG P0 TIME Figure 4. Optical Power Relations Optical Power Relations Many of the MAX3275/MAX3277 specifications relate to the input signal amplitude. When working with optical receivers, the input is sometimes expressed in terms of 6 Optical Sensitivity Calculation The input-referred RMS noise current (I N ) of the MAX3275/MAX3277 generally determines the receiver _______________________________________________________________________________________ Low-Noise, Fibre Channel Transimpedance Amplifiers 14.1IN (re +1) × 1000 Sensitivity =10 log dBm 2ρ(re -1) where ρ is the photodiode responsivity in A/W and IN is RMS current in Amps. Input Optical Overload The overload is the largest input that the MAX3275/ MAX3277 accept while meeting specifications. The optical overload can be estimated in terms of average power with the following equation: (2E - 3) (re +1) × 1000 Overload=10 log dBm 2ρ(re -1) Optical Linear Range The MAX3275/MAX3277 have high gain, which limits the output when the input signal exceeds 50µAP-P. The MAX3275/MAX3277 operate in a linear range (10% linearity) for inputs not exceeding: (50E - 6) (re +1) × 1000 Linear Range=10 log dBm 2ρ(re -1) Layout Considerations Noise performance and bandwidth will be adversely affected by capacitance at the IN pad. Minimize capacitance on this pad and select a low-capacitance photodiode. Assembling the MAX3275/MAX3277 in die form using chip and wire technology provides the best possible performance. Figure 5 shows a suggested layout for a TO header for the MAX3275/MAX3277. Special care should be taken to ensure that ESD at IN does not exceed 500V. Photodiode Filter Supply voltage noise at the cathode of the photodiode produces a current I = CPD ∆V/∆t, which reduces the receiver sensitivity (C PD is the photodiode capacitance). The filter resistor of the MAX3275/MAX3277, combined with an external capacitor, can be used to reduce this noise (see the Typical Application Circuit). Current generated by supply noise voltage is divided between CFILTER and CPD. The input noise current due to supply noise is (assuming the filter capacitor is much larger than the photodiode capacitance): INOISE = (VNOISE)(CPD) / (RFILTER)(CFILTER) If the amount of tolerable noise is known, the filter capacitor can be easily selected: CFILTER = (VNOISE)(CPD) / (RFILTER)(INOISE) For example, with maximum noise voltage = 100mVP-P, CPD = 0.85pF, RFILTER = 600Ω, and INOISE selected to be 350nA: CFILTER = (100mV)(0.85pF) / (600Ω)(350nA) = 400pF Wire Bonding For high-current density and reliable operation, the MAX3275/MAX3277 use gold metalization. Connections to the die should be made with gold wire only, using ball-bonding techniques. Wedge bonding is not recommended. Die thickness is typically 15 mils (0.4mm). Pad Coordinates VCC CFILTER PHOTODIODE CAP OUT+ OUTPUT POLARITIES REVERSED FOR MAX3277 OUT- MAX3275 CASE IS GROUND PAD# COORDINATES (µm) 1 16, 39 2 16, 372 3 16, 806 4 358, 806 5 358, 341 6 358, 36 7 362, -116 8 250, -116 9 138, -116 Figure 5. Suggested Layout for TO-46 Header _______________________________________________________________________________________ 7 MAX3275/MAX3277 sensitivity. To obtain a system bit error rate (BER) of 1E12, the signal-to-noise ratio must always exceed 14.1. The input sensitivity, expressed in average power, can be estimated as: Low-Noise, Fibre Channel Transimpedance Amplifiers MAX3275/MAX3277 Chip Topographies OUT(PAD 3) OUT+ (PAD 4) GND (PAD 2) MAX3275 GND (PAD 5) 0.047" (1.2mm) VCC (PAD 1) N.C. (PAD 6) INDEX FILTER (PAD 7) VCC (PAD 9) IN (PAD 8) 0.024" (0.6mm) 8 _______________________________________________________________________________________ Low-Noise, Fibre Channel Transimpedance Amplifiers OUT+ (PAD 3) OUT(PAD 4) GND (PAD 2) MAX3277 GND (PAD 5) VCC (PAD 1) 0.047" (1.2mm) N.C. (PAD 6) INDEX FILTER (PAD 7) VCC (PAD 9) IN (PAD 8) 0.024" (0.6mm) Chip Information TRANSISTOR COUNT: 301 SUBSTRATE: ISOLATED PROCESS: SiGe BIPOLAR 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 _____________________ 9 © 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc. MAX3275/MAX3277 Chip Topographies (continued)