19-4796; Rev 1; 6/00 KIT ATION EVALU E L B AVAILA 1.25Gbps/2.5Gbps, +3V to +5.5V, Low-Noise Transimpedance Preamplifiers for LANs The 1.25Gbps MAX3266 has a typical optical dynamic range of -24dBm to 0dBm in a shortwave (850nm) configuration or -27dBm to -3dBm in a longwave (1300nm) configuration. The 2.5Gbps MAX3267 has a typical optical dynamic range of -21dBm to 0dBm in a shortwave configuration or -24dBm to -3dBm in a longwave configuration. Features ♦ 200nA Input-Referred Noise (MAX3266) 500nA Input-Referred Noise (MAX3267) ♦ 920MHz Bandwidth (MAX3266) 1900MHz Bandwidth (MAX3267) ♦ 1mA Input Overload ♦ +3.0V to +5.5V Single-Supply Voltage Ordering Information PART TEMP. RANGE MAX3266CSA 0°C to +70°C 8 SO MAX3266C/D — Dice* MAX3267CSA 0°C to +70°C 8 SO — Dice* MAX3267C/D MAX3267ESA PIN-PACKAGE -40°C to +85°C MAX3267E/D 8 SO — Dice* *Dice are designed to operate over a -40°C to +140°C junction temperature (Tj) range, but are tested and guaranteed at TA = +25°C. Pin Configuration TOP VIEW Applications VCC 1 Gigabit Ethernet N.C. 1Gbps to 2.5Gbps Optical Receivers IN Fibre Channel 2 3 MAX3266 MAX3267 FILTER 4 8 GND 7 OUT+ 6 OUT- 5 GND SO Typical Application Circuit VCC 0.01µF 1.5k CFILTER 400pF VCC FILTER 0.1µF OUT+ PHOTODIODE IN 100Ω OUT- MAX3266 MAX3267 0.1µF LIMITING AMPLIFIER GND ________________________________________________________________ Maxim Integrated Products 1 For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. MAX3266/MAX3267 General Description The MAX3266 is a transimpedance preamplifier for 1.25Gbps local area network (LAN) fiber optic receivers. The circuit features 200nA input-referred noise, 920MHz bandwidth, and 1mA input overload. The MAX3267 provides a pin-for-pin compatible solution for communications up to 2.5Gbps. It features 500nA input-referred noise, 1.9GHz bandwidth, and 1mA input overload. Both devices operate from a +3.0V to +5.5V single supply and require no compensation capacitor. They also include a space-saving filter connection that provides positive bias for the photodiode through a 1.5kΩ resistor to VCC. These features allow easy assembly into a TO-46 or TO-56 header with a photodiode. MAX3266/MAX3267 1.25Gbps/2.5Gbps, +3V to +5.5V, Low-Noise Transimpedance Preamplifiers for LANs ABSOLUTE MAXIMUM RATINGS Supply Voltage (VCC - GND) .................................-0.5V to +6.0V IN Current..............................................................-4mA to +4mA FILTER Current......................................................-8mA to +8mA Voltage at OUT+, OUT- ...................(VCC - 1.5V) to (VCC + 0.5V) Continuous Power Dissipation (TA = +70°C) 8-Pin SO (derate 6.7mW/°C above +70°C)..................533mW Storage Temperature Range .............................-55°C to +150°C Operating Junction Temperature (die) ..............-55°C to +150°C Processing Temperature (die) .........................................+400°C Lead Temperature (soldering, 10s) .................................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS—MAX3266C/MAX3267C (VCC = +3.0V to +5.5V, TA = 0°C to +70°C, 100Ω load between OUT+ and OUT-. Typical values are at TA = +25°C, VCC = 3.3V, source capacitance = 0.85pF, unless otherwise noted.) (Note 1) PARAMETER CONDITIONS MIN TYP MAX UNITS 0.69 0.83 0.91 V 26 50 mA MAX3266 2260 2800 3400 MAX3267 1540 1900 2330 Input Bias Voltage Supply Current Transimpedance Differential, measured with 30µAp-p signal (40µAp-p for MAX3267) Ω Output Impedance Single ended (per side) 48 50 52 Ω Maximum Differential Output Voltage Input = 1mAp-p 185 250 415 mVp-p 1220 1500 1860 Ω Filter Resistor AC Input Overload 1.0 mAp-p DC Input Overload 0.65 mA Die, packaged in TO-56 header (Note 2) Input-Referred RMS Noise SO package (Note 2) Input-Referred Noise Density Small-Signal Bandwidth Low-Frequency Cutoff (Note 2) MAX3266 192 MAX3266 200 MAX3267 485 MAX3266 MAX3267 6.6 11.0 nA 655 pA/(Hz)1/2 MAX3266 750 920 1100 MAX3267 1530 1900 2420 -3dB, input ≤ 20µA DC 44 MAX3266 MAX3267 Transimpedance Linear Range Peak-to-peak, 0.95 < linearity < 1.05 Deterministic Jitter (Note 3) Power-Supply Rejection Ratio (PSRR) Output referred, f < 2MHz, PSRR = -20log (∆VOUT/∆VCC) 2 256 MHz kHz 30 40 µAp-p MAX3266 19 76 MAX3267 12 50 50 _______________________________________________________________________________________ ps ps dB 1.25Gbps/2.5Gbps, +3V to +5.5V, Low-Noise Transimpedance Preamplifiers for LANs (VCC = +3.0V to +5.5V, TA = -40°C to +85°C, 100Ω load between OUT+ and OUT-. Typical values are at TA = +25°C, VCC = 3.3V, source capacitance = 0.85pF, unless otherwise noted.) (Note 1) PARAMETER CONDITIONS Input Bias Voltage MIN TYP 0.67 0.83 0.97 V 26 53.2 mA Supply Current MAX UNITS Transimpedance Differential, measured with 40µAp-p signal 1470 1900 2355 Ω Output Impedance Single ended (per side) 47.7 50 52.1 Ω Maximum Differential Output Voltage Input = 1mAp-p 155 250 430 mVp-p 1210 1500 1865 Ω Filter Resistor AC Input Overload 1.0 DC Input Overload 0.65 mAp-p mA Input-Referred RMS Noise SO package (Note 2) 485 Input-Referred Noise Density (Note 2) 11.0 Small-Signal Bandwidth 1515 1900 Low-Frequency Cutoff -3dB, input ≤ 20µA DC Transimpedance Linear Range Peak-to-peak, 0.95 < linearity < 1.05 Deterministic Jitter (Note 3) 14 Power-Supply Rejection Ratio (PSRR) Output referred, f < 2MHz, PSRR = -20log (∆VOUT/∆VCC) 50 668 nA pA/(Hz)1/2 2550 24 MHz kHz 40 µAp-p 50 ps dB Note 1: Source Capacitance represents the total capacitance at the IN pin during characterization of noise and bandwidth parameters. Figure 1 shows the typical source capacitance vs. reverse voltage for the photodiode used during characterization of TO-56 header packages. Noise and bandwidth will be affected by the source capacitance. See the Typical Operating Characteristics for more information. Note 2: Input-Referred Noise is calculated as RMS Output Noise / (Gain at f = 10MHz). Noise Density is (Input-Referred Noise) / √bandwidth. No external filters are used for the noise measurements. Note 3: Deterministic Jitter is measured with the K28.5 pattern applied to the input [00111110101100000101]. _______________________________________________________________________________________ 3 MAX3266/MAX3267 ELECTRICAL CHARACTERISTICS—MAX3267E Typical Operating Characteristics (VCC = +3.3V, TA = +25°C, MAX3266/MAX3267 EV kit, source capacitance = 0.85pF, unless otherwise noted.) 210 200 190 CIN = 1.0pF CIN = 1.5pF CIN = 1.0pF 25 50 75 100 -25 0 25 50 75 100 1M 10M 100M 1G 10G FREQUENCY (Hz) DETERMINISTIC JITTER vs. INPUT AMPLITUDE INPUT-REFERRED RMS NOISE CURRENT vs. DC INPUT CURRENT SMALL-SIGNAL TRANSIMPEDANCE vs. TEMPERATURE 60 50 MAX3267 30 20 700 MAX3267 600 500 400 300 MAX3266 10 200 1 1000 10 100 MAX3266 BANDWIDTH vs. TEMPERATURE MAX3267 BANDWIDTH vs. TEMPERATURE 2400 940 CIN = 0.5pF 890 840 BANDWIDTH (MHz) MAX3266/67-07 990 CIN IS SOURCE CAPACITANCE 2300 PRESENTED TO DIE, INCLUDING PACKAGE PARASITIC, PIN DIODE, 2200 AND PARASITIC INTERCONNECT CAPACITANCE. 2100 CIN = 0.5pF 2000 740 25 50 75 JUNCTION TEMPERATURE (°C) 100 64 63 1500 -50 -25 0 25 50 75 100 OUTPUT AMPLITUDE vs. TEMPERATURE 350 300 250 200 150 100 CIN = 1.0pF 50 CIN = 1.5pF -25 0 25 50 75 JUNCTION TEMPERATURE (°C) -50 AMBIENT TEMPERATURE (°C) 1800 1600 CIN = 1.5pF MAX3267 65 60 1000 1900 1700 CIN = 1.0pF 66 61 DIFFERENTIAL DC INPUT CURRENT (µA) CIN IS SOURCE CAPACITANCE PRESENTED TO DIE, INCLUDING PACKAGE PARASITIC, PIN DIODE, AND PARASITIC INTERCONNECT CAPACITANCE. MAX3266 67 62 MAX3266 PEAK-TO-PEAK AMPLITUDE (µA) 1040 68 0 100 1090 69 AMPLITUDE (mV) 0 MAX3266/67-06 800 100 10 70 MAX3266/67-05 900 TRANSIMPEDANCE (dB) 70 1000 INPUT-REFERRED NOISE (nA) MAX3266/67-04 80 0 MAX3266/67-03 50 -50 JUNCTION TEMPERATURE (°C) 90 790 MAX3267 60 JUNCTION TEMPERATURE (°C) 100 40 65 55 CIN = 0.5pF 350 0 PEAK-TO-PEAK JITTER (ps) 450 400 170 4 500 CIN = 1.5pF 70 MAX3266/67-09 180 CIN = 0.5pF 550 MAX3266 TRANSIMPEDANCE (dB) 220 CIN IS SOURCE CAPACITANCE PRESENTED TO DIE, INCLUDING PACKAGE PARASITIC, PIN DIODE, AND PARASITIC INTERCONNECT CAPACITANCE. 600 FREQUENCY RESPONSE 75 MAX3266/67-08 INPUT-REFERRED NOISE (nA) 230 650 MAX3266/67-02 CIN IS SOURCE CAPACITANCE PRESENTED TO DIE, INCLUDING PACKAGE PARASITIC, PIN DIODE, AND PARASITIC INTERCONNECT CAPACITANCE. 240 MAX3267 INPUT-REFERRED NOISE vs. TEMPERATURE INPUT-REFERRED NOISE (nA) 250 MAX3266/67-01 MAX3266 INPUT-REFERRED NOISE vs. TEMPERATURE BANDWIDTH (MHz) MAX3266/MAX3267 1.25Gbps/2.5Gbps, +3V to +5.5V, Low-Noise Transimpedance Preamplifiers for LANs 100 0 -50 -25 0 25 50 AMBIENT TEMPERATURE (°C) _______________________________________________________________________________________ 75 100 1.25Gbps/2.5Gbps, +3V to +5.5V, Low-Noise Transimpedance Preamplifiers for LANs 4mV/div INPUT: 27-1 PRBS 30mV/div INPUT: 27-1 PRBS MAX3266/67-12 EYE DIAGRAM (INPUT = 20µAp-p) MAX3266/67-11 EYE DIAGRAM (INPUT = 1mAp-p) MAX3266/67-10 EYE DIAGRAM (INPUT = 10µAp-p) 5mV/div INPUT: 27-1 PRBS 160ps/div 80ps/div 160ps/div DC TRANSFER FUNCTION 30mV/div 150 MAX3266/67-14 INPUT: 27-1 PRBS 100 OUTPUT VOLTAGE (mVp-p) MAX3266/67-13 EYE DIAGRAM (INPUT = 1mAp-p) MAX3267 50 MAX3266 0 -50 -100 -150 80ps/div -200 -150 -100 -50 0 50 100 150 200 INPUT CURRENT (µA) Pin Description PIN NAME FUNCTION 1 VCC Supply Voltage 2 N.C. No Connection. Not internally connected. 3 IN 4 FILTER 5 GND Ground 6 OUT- Inverting Output. Current flowing into IN causes VOUT- to decrease. 7 OUT+ Noninverting Output. Current flowing into IN causes VOUT+ to increase. 8 GND Ground Amplifier Input Provides bias voltage for the photodiode through a 1.5kΩ 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 MAX3266/MAX3267 Typical Operating Characteristics (continued) (VCC = +3.3V, TA = +25°C, MAX3266/MAX3267 EV kit, source capacitance = 0.85pF, unless otherwise noted.) Detailed Description The MAX3266 is a transimpedance amplifier designed for 1.25Gbps fiber optic applications. Figure 2 is a functional diagram of the MAX3266, which comprises a transimpedance amplifier, a voltage amplifier, an output buffer, an output filter, and a DC cancellation circuit. The MAX3267, a transimpedance amplifier designed for 2.5Gbps fiber optic applications, shares similar architecture with the MAX3266. 1.85 1.70 1.40 1.25 1.10 0.95 0.80 0.65 0.50 1 2 3 4 Voltage Amplifier The voltage amplifier converts single-ended signals to differential signals and introduces a voltage gain. 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 load resistors and the external load resistor. In the typical operating circuit, this creates a voltage-divider with gain of 1/2. The MAX3266 can also be terminated with higher output impedances, which increases gain and output voltage swing. For optimum supply-noise rejection, the MAX3266 should be terminated with a differential load. If a singleended output is required, the unused output should be similarly terminated. The MAX3266 will not drive a DCcoupled, 50Ω grounded load. 1.55 0 Transimpedance Amplifier The signal current at the input flows into the summing node of a high-gain amplifier. Shunt feedback through RF converts this current to a voltage with gain of approximately 2.2kΩ (1.0kΩ for MAX3267). Schottky diodes clamp the output voltage for large input currents, as shown in Figure 3. Output Buffer MAX3266/67 fig01 2.00 CAPACITANCE (pF) MAX3266/MAX3267 1.25Gbps/2.5Gbps, +3V to +5.5V, Low-Noise Transimpedance Preamplifiers for LANs 5 REVERSE BIAS (V) Figure 1. Typical Photodiode Capacitance vs. Bias Voltage MAX3266 RF TRANSIMPEDANCE AMPLIFIER VOLTAGE AMPLIFIER OUTPUT BUFFER 50Ω OUTPUT FILTER OUT+ OUT- IN 50Ω LOWPASS FILTER VCC VCC GND DISABLE 1.5k DC CANCELLATION CIRCUIT FILTER Figure 2. MAX3266 Functional Diagram 6 _______________________________________________________________________________________ 1.25Gbps/2.5Gbps, +3V to +5.5V, Low-Noise Transimpedance Preamplifiers for LANs MAX3266/MAX3267 AMPLITUDE AMPLITUDE INPUT FROM PHOTODIODE TIME TIME OUTPUT (SMALL SIGNALS) OUTPUT (LARGE SIGNALS) Figure 3. MAX3266 Limited Output INPUT (AFTER DC CANCELLATION) Figure 4. DC Cancellation Effect on Input Output Filter The MAX3266 includes a one-pole lowpass filter that limits the circuit bandwidth and improves noise performance. DC Cancellation Circuit The DC cancellation circuit uses low-frequency feedback to remove the DC component of the input signal (Figure 4). This feature centers the input signal within the transimpedance amplifier’s linear range, thereby reducing pulse-width distortion on large input signals. 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% duty cycle. A duty cycle significantly different from 50% will cause the MAX3266 to generate pulse-width distortion. DC cancellation current is drawn from the input and creates noise. For low-level signals with little or no DC component, this is not a problem. Amplifier noise will increase for signals with significant DC component (see Typical Operating Characteristics). Applications Information Optical Power Relations Many of the MAX3266 specifications relate to the input signal amplitude. When working with fiber optic receivers, the input is usually expressed in terms of average optical power and extinction ratio. Figure 5 shows relations that are helpful for converting optical power to input signal when designing with the MAX3266. Optical power relations are shown in Table 1; the definitions are true if the average duty cycle of the input data is 50%. Optical Sensitivity Calculation The input-referred RMS noise current (I N ) of the MAX3266 generally determines the receiver sensitivity. To obtain a system bit error rate (BER) of 1E-12, the SNR ratio must always exceed 14.1. The input sensitivity, expressed in average power, can be estimated as: 14.1 I r + 1 N e 1000 dBm Sensitivity = 10 log 2ρ r − 1 (e ( ) ) Where ρ is the photodiode responsivity in A/W. Input Optical Overload The overload is the largest input that the MAX3266 accepts while meeting specifications. The optical overload can be estimated in terms of average power with the following equation: 1mA Overload = 10 log 1000 dBm 2ρ _______________________________________________________________________________________ 7 Noise performance and bandwidth will be adversely affected by capacitance at the IN pin. Minimize capacitance on this pin and select a low-capacitance photodiode. Assembling the MAX3266 in die form using chip and wire technology provides the best possible performance. Figure 6 shows a suggested layout for a TO header. The SO package version of the MAX3266 is offered as an easy way to characterize the circuit and become familiar with the circuit’s operation, but it does not offer optimum performance. When using the SO version of the MAX3266, the package capacitance adds approximately 0.3pF at the input. The PC board between the MAX3266 input and the photodiode also adds parasitic capacitance. Keep the input line short, and remove power and ground planes beneath it. PI OPTICAL POWER MAX3266/MAX3267 1.25Gbps/2.5Gbps, +3V to +5.5V, Low-Noise Transimpedance Preamplifiers for LANs PAVG PO TIME Figure 5. Optical Power Relations Table 1. Optical Power Relations PARAMETER SYMBOL Average Power PAVG RELATION 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 = 2PAVG (re) / (re + 1) PAVG = (P0 + P1) / 2 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 MAX3266, 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) Optical Linear Range The MAX3266 has high gain, which limits the output when the input signal exceeds 30µAp-p (40µAp-p for MAX3267). The MAX3266 operates in a linear range for inputs not exceeding: ( ) 30µA re + 1 1000 dBm Linear Range = 10log 2ρ re − 1 ( ) Layout Considerations Use good high-frequency design and layout techniques. The use of a multilayer circuit board with separate ground and power planes is recommended. Connect the GND pins to the ground plane with the shortest possible traces. 8 For example, with maximum noise voltage = 100mVp-p, CPD = 0.85pF, RFILTER = 1.5kΩ, and INOISE selected to be 100nA (1/2 of the MAX3266’s input noise): CFILTER = (100mV)(0.85pF) / (1500Ω)(100nA) = 570pF Wire Bonding For high current density and reliable operation, the MAX3266 uses gold metalization. Connections to the die should be made with gold wire only, using ballbonding techniques. Wedge bonding is not recommended. Die thickness is typically 15mils (0.375mm). _______________________________________________________________________________________ 1.25Gbps/2.5Gbps, +3V to +5.5V, Low-Noise Transimpedance Preamplifiers for LANs MAX3266/MAX3267 TOP VIEW OF TO-56 HEADER VCC CFILTER PHOTODIODE OUT+ OUT- MAX3266/MAX3267 CASE IS GROUND Figure 6. Suggested Layout for TO-56 Header Chip Topographies MAX3267 MAX3266 FILTER INPUT VCC FILTER GND GND INPUT GND GND 0.050" (1.25mm) OUT- OUT+ VCC 0.050" (1.25mm) OUT- 0.030" (0.75mm) OUT+ 0.030" (0.75mm) TRANSISTOR COUNT: 320 SUBSTRATE CONNECTED TO GND _______________________________________________________________________________________ 9 1.25Gbps/2.5Gbps, +3V to +5.5V, Low-Noise Transimpedance Preamplifiers for LANs SOICN.EPS MAX3266/MAX3267 Package Information 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. 10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.