19-4223; Rev 0; 7/08 KIT ATION EVALU E L B A AVAIL Analog CATV Transimpedance Amplifier The MAX3660 high-linearity analog RF transimpedance amplifier (TIA) is intended for passive optical network (PON) video receiver applications. With 66dBΩ maximum variable gain and integrated uptilt, the MAX3660 provides 23dBmV/channel ±1dB at 870MHz (19dBmV/channel at 47MHz) for optical inputs between +2dBm to -8dBm (at 4.2% OMI) using simple feed-forward automatic gain control (AGC). It can also be configured with feedback AGC for even greater dynamic range. CNR is better than 48dB from 47MHz to 870MHz (1.0A/W photodiode and -165dB/Hz RIN) at -8dBm with 4.2% OMI, or -6dBm with 3.3% OMI. CSO and CTB are better than -61dBc and -65dBc, respectively. The device supports extended frequency operation to > 1000MHz. The very low true-TIA input impedance accommodates a variety of photodiodes, eliminating the need for an input matching network and improving yield. Applications FTTH Optical Network Termination (ONT) Features ♦ Pin Compatible with MAX3654 ♦ Operates to > 1000MHz ♦ 23dBmV/ch Output at 870MHz ♦ 4.5pA/Hz1/2 Amplifier EIN without Photodiode ♦ 58dBm OIP2 ♦ 24dBm OIP3 ♦ No Input Matching Required ♦ Single +5V Supply ♦ 650mW Dissipation ♦ -40°C to +85°C Operating Temperature Range Ordering Information PART MAX3660ETE+ TEMP RANGE PIN-PACKAGE -40°C to +85°C 16 TQFN-EP* +Denotes a lead-free/RoHS-compliant package. *EP = Exposed pad. Pin Configuration VCC OUT+ OUT- VCC TOP VIEW 12 11 10 9 TEST 13 GND 14 MAX3660 + VCC 1 EP* 2 3 4 VCC GND 16 IN- GND 15 IN+ Typical Application Circuit appears at end of data sheet. 8 GND 7 HYST 6 MUTE 5 VAGC THIN QFN-EP (4mm × 4mm) *THE EXPOSED PAD MUST BE CONNECTED TO GROUND. ________________________________________________________________ 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 MAX3660 General Description MAX3660 Analog CATV Transimpedance Amplifier ABSOLUTE MAXIMUM RATINGS Supply Voltage Range, VCC........................................-0.3V to +5.5V IN+, IN-, VAGC, MUTE, HYST, TEST..................................(VEE - 0.4V) to (VCC + 0.4V) Output Current (OUT+, OUT-) ............................................60mA Maximum Voltage (OUT+, OUT-) ............................(VCC + 0.4V) Continuous Power Dissipation (TA = +70°C) 16-Pin TQFN-EP (derate 16.9mW/°C above +70°C)..1349mW Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-55°C to +175°C Lead Temperature (soldering, 10s) .................................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. DC ELECTRICAL CHARACTERISTICS (VCC = +4.75V to +5.25V, TA = -40°C to +85°C. Typical values are at VCC = +5V, TA = +25°C, unless otherwise noted.) (Note 1) PARAMETER Supply Current Gain Control Input Current MUTE Input High MUTE Input Low MUTE Input Current SYMBOL CONDITIONS MIN ICC I VAGC VVAGC = 1.4V VIH TYP MAX UNITS 130 180 mA -15 -200 μA 2.0 V VIL IIL, IIH VMUTE = 0.5V, 2.0V 0.5 V ±30 μA AC ELECTRICAL CHARACTERISTICS (VCC = +4.75V to +5.25V, TA = -40°C to +85°C, output ZL = 75Ω, unless otherwise noted. Typical values are at VCC = +5V, TA = +25°C, unless otherwise noted.) PARAMETER SYMBOL Frequency Response Flatness (Notes 2, 3, 4) CONDITIONS MIN 47MHz to 1000MHz ±1.0 47MHz, VVAGC = 0.175V (Note 2) ZT 66 47MHz, VVAGC = 0.5V (Note 2) 54 56.5 58 47MHz, VVAGC = 1.4V (Note 2) 45.5 48 49.5 47MHz, VVAGC = 1.6V Linear, 870MHz vs. 47MHz (Note 4) Gain Control Stability 0.175V VVAGC 1.4V, RHYST = open (Notes 2, 5) Output Second-Order Intercept OIP2 47MHz to 870MHz, 0.175V VVAGC 1.4V (Note 6) Output Third-Order Intercept OIP3 47MHz to 870MHz, 0.175V VVAGC 1.4V (Note 6) UNITS dB 66 63.5 Gain Tilt 2 MAX ±0.9 47MHz, VVAGC = 0V Transimpedance, Differential TYP 47MHz to 870MHz 67.5 dB 46.5 3.8 20 4.5 5.0 dB ±0.8 ±2.0 dB 58 dBm 24 dBm _______________________________________________________________________________________ Analog CATV Transimpedance Amplifier (VCC = +4.75V to +5.25V, TA = -40°C to +85°C, output ZL = 75Ω, unless otherwise noted. Typical values are at VCC = +5V, TA = +25°C, unless otherwise noted.) PARAMETER Equivalent Input Noise, Including Photodiode SYMBOL CONDITIONS EIN 47MHz to 870MHz, 0.175V VVAGC 1.4V (Notes 2, 4) Gain Control Hysteresis (Notes 1, 7) MIN TYP MAX UNITS 5.5 7.3 pA/Hz1/2 RHYST = open ±0.14 RHYST = GND ±0.75 VMUTE 0.8V, 47MHz Transimpedance, Mute RF Output Return Loss -S22 dB (optical) 20 47MHz to 870MHz (Notes 4, 8) dB 20 dB Note 1: DC parameters are tested at TA = +25°C and +85°C. Note 2: Guaranteed by design and characterization. Note 3: Frequency response flatness is the maximum difference between the frequency response at any point and a line connecting the end points of 47MHz and 870MHz. Note 4: Measured using the MAX3660 EV kit circuit in Figure 4 with an Excelight SXT5241-Q/GPA triplexer (8mm photodiode lead length). Note 5: Gain control stability is the maximum variation in transimpedance (over process, voltage, and temperature) for any valid VAGC voltage. Note 6: OIP2 and OIP3 values are tested with tones at 800MHz and 850MHz. Note 7: Hysteresis is referred to optical gain, equivalent to two times electrical gain (dB). Note 8: Not including balun. VCC 48dBΩ TO 54dBΩ 5Ω 1nH 0.5pF 5nH 0.3pF 0.5pF 5Ω IN+/- 54dBΩ TO 60dBΩ TIA OUT+/- TO TIA 1nH 0.5pF 5nH 60dBΩ TO 66dBΩ 0.3pF MAX3660 MUTE Figure 1. Photodiode and Header Model HYST VAGC Figure 2. Functional Diagram _______________________________________________________________________________________ 3 MAX3660 AC ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VCC = +5.0V, TA = +25°C, unless otherwise noted. CNR, CSO, and CTB are for the MAX3660 EV Kit at PIN = -8dBm, with channels above 350MHz attenuated 6dB.) VVAGC = 0.1V 70 0.6 60 55 DEVIATION (dB) 65 F = 875MHz 60 55 50 50 0.2 TA = +25°C 0 -0.2 -0.4 F = 47MHz 45 VVAGC = 1.6V TA = +85°C -0.8 40 40 0 -1.0 0.1 200 400 600 800 1000 1200 1400 1600 10 1 0 200 400 600 800 FREQUENCY (MHz) VAGC (V) FREQUENCY (MHz) DEVIATION FROM IDEAL GAIN vs. VAGC (FREQUENCY = 47MHz, TA = -40°C, +25°C, +85°C) OIP2, OIP3 vs. VAGC EQUIVALENT INPUT NOISE vs. FREQUENCY 70 TA = +25°C 6.6 0 -0.2 TA = +85°C 60 NOISE (pA/H1/2) 0.2 -0.4 6.8 OIP2 OIP2, OIP3 (dBm) 0.4 7.0 50 40 5.8 TA = -40°C 5.0 20 0.4 0.8 1.2 1.6 0 0.5 1.0 1.5 0 2.0 100 200 300 400 500 600 700 800 900 VAGC (V) VAGC (V) FREQUENCY (MHz) CNR vs. FREQUENCY (110 CHANNELS, OMI = 4.2%/2.1%) CSO, CTB vs. FREQUENCY (110 CHANNELS, PIN = +2dBm, OMI = 4.2%/2.1%) S22 NORMALIZED TO 75Ω PIN = -6dBm -10 -60 CS S22 (dB) PIN = -2dBm -65 DUT AND BALUN -15 -20 DUT ONLY CTB -70 PIN = -8dBm -25 CTB -75 PIN = -8dBm -5 PIN = +2dBm PIN = -2dBm MAX3660 toc09 CSO -55 0 MAX3660 toc08 PIN = +2dBm 50 -50 MAX3660 toc07 60 CSO, CTB (dBc) 0 40 TA = +25°C 6.0 5.2 -1.0 45 6.2 5.4 30 -0.8 55 TA = +85°C 6.4 5.6 OIP3 -0.6 1000 MAX3660 toc06 TA = -40°C 0.6 80 MAX3660 toc05 0.8 MAX3660 toc04 1.0 -30 PIN = -6dBm 0 100 200 300 400 500 600 700 800 900 1000 FREQUENCY (MHz) 4 TA = -40°C 0.4 -0.6 45 DEVIATION FROM GAIN (dB) 0.8 65 GAIN (ZT) (dBΩ) GAIN (ZT) (dBΩ) 70 1.0 MAX3660 toc02 75 75 MAX3660 toc01 80 DEVIATION FROM LINEAR TILT vs. FREQUENCY (VVAGC = 0 TO 1.6V; TA = -40°C, +25°C, +85°C) GAIN (ZT) vs. VAGC (TA = -40°C, +25°C, +85°C) MAX3660 toc03 GAIN (ZT) vs. FREQUENCY (VVAGC = 0.10V, 0.175V, 0.25V, 0.35V, 0.7V, 1.05V, 1.4V, 1.6V; TA = -40°C, +25°C, +85°C) CNR (dB) MAX3660 Analog CATV Transimpedance Amplifier -35 -80 0 200 400 600 FREQUENCY (MHz) 800 1000 0 200 400 600 FREQUENCY (MHz) _______________________________________________________________________________________ 800 1000 Analog CATV Transimpedance Amplifier PIN NAME 1, 4, 9, 12 VCC FUNCTION 2 IN+ Positive Analog Input. Connect to photodiode cathode. 3 IN- Negative Analog Input. Connect to photodiode anode. 5 VAGC AGC Control Input. See the Gain (ZT) vs. Frequency graph. 6 MUTE Active-Low Mute Control Input. VMUTE < 0.8V to disable output. 7 HYST AGC Hysteresis Control Input. A resistor from HYST to GND controls the hysteresis level. 8, 14, 15, 16 GND Supply Ground 10 OUT- Negative RF Output 11 OUT+ Positive RF Output 13 TEST Reserved for test. Connect to GND for normal operation. — EP +5.0V Supply Exposed Pad. The exposed pad must be soldered to the circuit board ground for proper thermal and electrical performance. Detailed Description The MAX3660 variable gain TIA has differential ACcoupled photocurrent inputs and 75Ω differential RF output. When used with a low-cost operational amplifier, photodiode assembly, bias network, and balun, the MAX3660 provides a complete high-performance BPON/GPON video receiver with a simple and effective feed-forward AGC. It can also be used with feedback AGC. Low-Noise Variable-Gain Amplifier The low-noise differential input is designed to be ACcoupled to the anode and cathode of the analog photodiode in a PON triplexer. The maximum input current to achieve rated linearity is 1.675mAP-P. Very low TIA input impedance provides excellent frequency response with no (internal or external) compensation between photodiode and amplifier, thus simplifying design, manufacturing, and photodiode selection. VAGC and Hysteresis Control The overall transimpedance is controlled using the VAGC input pin. See the Typical Operating Characteristics for descriptions of the transimpedance, OIP2 (CSO), and OIP3 (CTB) performance for VAGC voltages between 0 and 1.8V. The MAX3660 has a very flat and stable gain vs. voltage characteristic in the range 0.175V ≤ VVAGC ≤ 1.4V, enabling a simple feed-forward AGC based on average optical power level as measured by the photodiode DC current (see Figure 4 for the EV kit schematic). Feedback AGC can be used to achieve a wider dynamic range, in which case the VAGC voltage would be controlled by an external power detector, such as the MAX2014, typically through a microcontroller interface. In this case, the maximum voltage at VAGC should be kept below approximately 1.65V to maintain adequate linearity levels for typical GPON applications. The forward signal path is implemented with three switched variable gain stages, each covering one-third of the total dynamic range. When the voltage input at VAGC crosses the points on the Gain (ZT) vs. VAGC curve where a new stage is selected (VVAGC = 350mV and VVAGC = 700mV), there can be a small (approximately 50ns) deviation in the output, causing an interruption to the CATV signal. Hysteresis is provided for the VAGC input to prevent the output signal from dithering when the average optical input level is very close to one of these two switching points. The amount of hysteresis can be controlled by the value of RHYST, and is minimum (0.14dB) when RHYST is open. RF Output and Cable Tilt Compensation The MAX3660 includes integrated cable compensation (uptilt). With a photodiode assembly similar to that described in Figure 1, the output at 870MHz is 4dB higher compared to the output at 47MHz. About half of the uptilt is due to the combination of photodiode capacitance and the inductance of the triplexer leads, and half is internal to the MAX3660. _______________________________________________________________________________________ 5 MAX3660 Pin Description MAX3660 Analog CATV Transimpedance Amplifier RF Output and Input Stage The differential outputs should be connected to a balun transformer to produce a single-ended 75Ω output. If the MAX3660 is used to drive a single-ended postamplifier, the use of a balun is recommended (refer to Maxim Reference Design HFRD-22.4) to achieve adequate linearity and noise performance. With a typical low-cost balun, output return loss (-S22) is better than 15dB up to 550MHz and is limited by the balun performance. When MUTE is logic-low, the transimpedance is less than 20dBΩ. Applications Information Photodiode/TIA Interface The MAX3660 is designed to provide a 23dBmV/channel output at 870MHz with excellent CSO, CTB, and CNR, and its frequency response extends well beyond 1000MHz. The RF output has 4dB ±1dB of uptilt and ±0.9dB of flatness (47MHz to 870MHz) when used with a photodiode and assembly having characteristics similar to those shown in Figure 1, which is consistent with a typical low-cost FTTH triplexer connected by 5mm leads to matched vias. The MAX3660’s very low input impedance (approximately 10Ω) also provides tolerance to variations in photodiode and assembly electrical characteristics. It is particularly important to provide electrical symmetry in the anode and cathode connections, including the triplexer/ROSA lead routing and PCB mounting configuration. Consult the EV kit and Maxim reference designs for examples of good layout techniques. With typical optical transmitter characteristics, the MAX3660 achieves CSO and CTB better than -65dBc and achieves CNR (including amplifier noise, photodiode shot noise, and transmitter RIN) of 48dB (at -6dBm or greater with OMI = 3.3%, or at -8dBm or greater with OMI = 4.2%) between 47MHz and 870MHz. Refer to the MAX3660 EV kit data sheet for a description of the setup used for CSO, CTB, and CNR typical operating characteristics measurements. To achieve optimum CNR performance, the AGC should be configured so that the MAX3660’s gain is greatest (VVAGC ≤ 0.175V) at the lowest intended optical input level, typically -6dBm or -8dBm. To maintain CTB and CSO performance, care should also be exercised when designing the AGC so that the maximum operating VAGC level is limited to approximately 1.6V. Operating 6 with input signal levels greater than 1.6mAP-P can result in a reduction in linearity due to clipping. Photodiode Bias Network A combination of resistors and inductors, such as shown in Figure 3, provides DC bias to the photodiode. The series connection of two inductors and one resistor is intended to mitigate effects of inductor selfresonance. The DC voltage drop across the lower resistor provides an effective means to measure average optical power for use as a signal strength indicator and/or feed-forward AGC. The value of the resistors can be adjusted to vary the feed-forward gain. Depending on the specific photodiode characteristics and desired frequency response, between 5V and 12V should normally be used for VPD. VPD 0.1μF 10μH 1.8kΩ BEAD 1kΩ 0.001μF TIA IN+ 0.001μF 1kΩ 1.8kΩ BEAD 10μH Figure 3. Photodiode Bias Network _______________________________________________________________________________________ TIA IN- VMON Analog CATV Transimpedance Amplifier Uptilt The integrated uptilt results in equal input levels producing an output voltage that is 4dB greater at 870MHz compared to 47MHz, eliminating the loss normally associated with an external passive tilt network. The amount of uptilt can be varied by adjusting the triplexer lead length, or by adding small inductors in series with the anode and cathode, to compensate for photodiodes/triplexers that differ significantly from Figure 1. ⎡ 175mV ⎤ ZT(dBΩ) = 66dBΩ + 20 log ⎢ ⎥ , ( 0..175V ≤ V VAGC ≤ 1.4V ) ⎢⎣ V VAGC (mV ) ⎥⎦ The gain at 870MHz is 4dB greater (70dBΩ at VVAGC = 0.175V) because of the uptilt, although the amount of uptilt can be modified as described above. Between 0 and 0.175V the gain is constant, and above 1.5V it falls off relatively quickly. Operation above VVAGC = 1.6V should be avoided to obtain adequate linearity performance. The high-impedance VAGC input should be driven by a source (op amp, DAC, etc.) capable of sinking up to 200µA. Feed-Forward AGC With a feed-forward circuit like that of the EV kit, the MAX3660 provides a constant (±1dB) output of 19dBmV/channel at 47MHz and 23dBmV/channel at 870MHz, for optical input levels ranging between -8dBm and +2dBm at OMI = 4.2%. Feedback AGC The VAGC voltage can also be controlled from a power detector, such as the MAX2014 or MAX9933, for feedback AGC. It is important to note that the Gain (ZT) vs. VAGC characteristic includes hysteresis at the two points where the input stage switches gain (350mV and 700mV), which can cause problems such as limit-cycle oscillation with continuous analog feedback implementations. The feedback circuit should be designed to avoid oscillation or dithering. Equivalent Input Noise The typical equivalent input referred noise (EIN) of the MAX3660 with a photodiode connected at the input is 5.5pA/Hz1/2, yielding 48dB or better CNR under normal BPON/GPON conditions. Without a photodiode connected, the typical EIN is 4.5pA/Hz1/2. RF Output The RF output should be connected to the MAX3660 using AC-coupling capacitors and a balun transformer to achieve the desired noise and linearity performance. Without the capacitors, shorting OUT+ and OUTtogether, or shorting OUT+ or OUT- to ground, can draw sufficient current to damage the output stage. EV Kit Circuit The MAX3660 EV kit circuit shown in Figure 4 was used to collect the data in the Typical Operating Characteristics figures. When connected to a photodiode-equipped triplexer, the EV kit circuit provides a complete receiver, including photodiode bias, feed-forward AGC, and output transformer. Jumper JU1 controls the MUTE input, JU3 sets the amount of hysteresis, and JU2 controls the input of the op amp driving the VAGC input. Install JU2 to enable feed-forward VAGC, or alternatively, the gain can be controlled by TP6 with JU2 removed. _______________________________________________________________________________________ 7 MAX3660 Gain vs. VAGC Voltage The overall transimpedance at 47MHz is related to the voltage at VAGC by the relation: MAX3660 Analog CATV Transimpedance Amplifier VPD VPD TP13 C3 0.1μF VPD VCC TP1 L2 10μH TP2 C14 33μF TP5 GND L1 1.8kΩ BEAD C7 0.1μF 15 16 VCC 14 GND GND 1 R1 1kΩ 13 GND VCC TEST VCC VCC C4 0.001μF IN+ 3 C8 0.1μF R21 1kΩ OUT+ U1 C2 0.001μF U5 C8 0.1μF 12 C1 0.001μF 2 11 IN- OUT- 10 EP VCC 4 VCC VCC VCC MUTE 6 HYST 7 U8 CX2038 C5 0.001μF MAX3660 VAGC 5 L5 1.8kΩ BEAD C9 0.1μF 9 GND 8 R3 100kΩ TP3 L6 10μH R5 100kΩ R22 OPEN TP4 JP3 C11 1μF C6 1μF U2 R4 100kΩ R9 20kΩ JP1 JP2 TP6 C10 1μF R6 1kΩ R7 OPEN R8 1kΩ VCC Figure 4. MAX3660 EV Kit Schematic 8 C13 33μF VCC _______________________________________________________________________________________ J2 Analog CATV Transimpedance Amplifier VPD 0.1μF 10μH +5V 1.8kΩ BEAD VCC 1kΩ TEST MAX3660 0.001μF 0.001μF -8dBm TO +2dBm, -6dBm TO +2dBm IN+ OUT+ IN- OUT- CX2038 75Ω 0.001μF 0.001μF 1kΩ HYST 1.8kΩ BEAD RHYST MUTE VAGC GND EP +5V 100kΩ 1μF 10μH 100kΩ Package Information Chip Information PROCESS: SiGe BiPOLAR SUBSTRATE: SOI For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 16 TQFN-EP T1644+3 21-0139 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 © 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc. MAX3660 Typical Application Circuit