19-4763; Rev 0; 7/98 KIT ATION EVALU E L B A AVAIL 250MHz, Low-Power, High-Output-Current, Differential Line Driver ____________________________Features ♦ 250MHz -3dB Bandwidth (AV = +2V/V) ♦ 1400V/µs Slew Rate ♦ 67dB at 10MHz CMR ♦ 0.01%/0.01° Differential Gain/Phase ♦ ±6V Differentially into 100Ω Output Drive ♦ 1mA Shutdown Capability ♦ 12.5mA Quiescent Supply Current ♦ Available in 14-Pin Narrow SO Package Ordering Information PART MAX4142ESD TEMP. RANGE -40°C to +85°C PIN-PACKAGE 14 SO Pin Configuration TOP VIEW VEE 1 14 VCC IN+ 2 ________________________Applications MAX4142 N.C. 3 Video Twisted-Pair Driver 12 SENSE+ 11 GND SHDN 4 Differential Pulse Amplifier 13 OUT+ 10 SENSE- N.C. 5 High-Speed Instrumentation Amplifier IN- 6 9 OUT- Low-Noise Differential Receivers VEE 7 8 VCC Differential ADC Driver SO N.C. = NOT INTERNALLY CONNECTED Typical Application Circuit IN+ Rt Rt SENSE+ SENSE IN75Ω OUT+ MAX4142 GND OUT- IN+ MAX4144 IN- 75Ω COAX VOUT OUT 75Ω SENSE- Rt Rt REF TWISTED-PAIR TO COAX-CABLE CONVERTER ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 408-737-7600 ext. 3468. MAX4142 General Description The MAX4142 differential line driver combines highspeed performance with fully symmetrical differential inputs and outputs. With an internally set +2V/V closedloop gain, the MAX4142 is ideal for driving backterminated cables and transmission lines. This device utilizes laser-trimmed thin-film resistors and common-mode cancellation circuitry to deliver an outstanding 67dB at 10MHz common-mode rejection (CMR). Using current-feedback techniques, the MAX4142 achieves a 250MHz -3dB (AV = +2V/V) bandwidth, a 70MHz 0.1dB bandwidth, and a 1400V/µs slew rate. Excellent differential gain/phase error and noise specifications make this amplifier an excellent choice for a wide variety of video and RF signal-processing applications. The MAX4142 operates from ±5V power supplies and requires only 12.5mA of quiescent current. The output stage is capable of driving a 100Ω load to ±6V (differentially) or to ±3V (single-ended). The MAX4142 is available in a space-saving 14-pin SO package. For a pin-compatible, higher speed differential line driver, see the MAX4147 data sheet. MAX4142 250MHz, Low-Power, High-Output-Current, Differential Line Driver ABSOLUTE MAXIMUM RATINGS Supply Voltage (VCC to VEE)................................................+12V Voltage on Any Pin to Ground..........(VEE - 0.3V) to (VCC + 0.3V) Input Current (IN_)............................................................±10mA Short-Circuit Duration (VOUT to GND) ................................10sec Continuous Power Dissipation (TA = +70°C) Plastic SO (derate 8.3mW/°C above +70°C) ................667mW Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10sec) .............................+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 = +5V, VEE = -5V, SHDN = 0, RL = ∞, TA = TMIN to TMAX, unless otherwise noted. Typical values specified at TA = +25°C.) PARAMETER SYMBOL Operating Supply Voltage Input Offset Voltage CONDITIONS Guaranteed by PSR test MIN TYP ±4.5 UNITS ±5.5 V 8 mV VOS VIN = 0 TCVOS VIN = 0 3 IB VIN = 0 10 25 µA Input Offset Current IOS VIN = 0 0.2 2.5 µA Input Capacitance CIN 1 pF Differential Input Resistance RIN 1 MΩ Input Offset Voltage Drift Input Bias Current Differential Input Voltage Range Common-Mode Input Voltage Range Gain VCM AV Gain Error Gain Drift 0.4 MAX Guaranteed by output voltage swing test -3.0 Guaranteed by CMR test -1.7 3.0 1.7 -1V ≤ VOUT ≤ 1V, RL = 53Ω 2 -1V ≤ VOUT ≤ 1V, RL = 53Ω 0.3 RL = 53Ω µV/°C V V V/V 2 % 20 ppm/°C Common-Mode Rejection CMR VCM = ±1.7V 55 80 dB Power-Supply Rejection PSR VS = ±4.5V to ±5.5V 65 95 Quiescent Supply Current ICC, IEE Shutdown Supply Current ICC, SHDN Output Voltage Swing VOUT Output Current Drive IOUT Output Resistance ROUT SHDN Logic-High Threshold VIH SHDN Logic-Low Threshold VIL VIN = 0 VSHDN ≥ 2V, VIN = 0 18 mA 1.0 2.0 mA Single-ended, RL = ∞ 3.0 3.4 Differential, RL = ∞ 6.0 6.8 Single-ended, RL = 26.5Ω 2.0 2.4 Differential, RL = 53Ω 4.0 4.8 RL = 20Ω 120 75 Ω 0.8 tON 500 3.5 VSHDN = 0 V V tOFF 2 mA 2.0 Disable Time to Shutdown ISHDN V 0.1 Enable Time from Shutdown SHDN Input Current dB 12.5 66 _______________________________________________________________________________________ ns µs 150 µA 250MHz, Low-Power, High-Output-Current, Differential Line Driver (VCC = +5V, VEE = -5V, SHDN = 0V, RL = 150Ω differential, CONDITIONS TA = TMIN to TMAX, unless otherwiseMIN noted. Typical PARAMETER SYMBOL TYP values MAX specified UNITSat T-3dB A = +25°C.) Bandwidth BW(-3dB) VOUT ≤ 0.1VRMS 250 MHz Full-Power Bandwidth FPBW VOUT = 2Vp-p 180 MHz 0.1dB Bandwidth BW(0.1dB) Common-Mode Rejection CMR Slew Rate 70 MHz f = 10MHz, VCM = ±2V 67 dB 1400 V/µs Differential, -2V ≤ VOUT ≤ +2V SR Settling Time VOUT ≤ 0.1VRMS -1V ≤ VOUT ≤ +1V tS to 0.1% 25 to 0.01% 45 ns Differential Gain DG f = 3.58MHz 0.01 % Differential Phase DP f = 3.58MHz Input Voltage Noise en Input Current Noise in Spurious-Free Dynamic Range SFDR 0.01 degrees f = 10kHz 8 nV/√Hz f = 1MHz to 100MHz 80 µVRMS f = 10kHz 2 pA√Hz f = 1MHz to 100MHz 20 nARMS fC = 500kHz, VOUT = 1Vp-p, RS = 50Ω, Figure1 -84 fC = 10MHz, VOUT = 1Vp-p, RS = 50Ω, Figure1 -76 dBc __________________________________________Typical Operating Characteristics (VCC = +5V, VEE = -5V, SHDN = 0, RL = 150Ω differential, TA = +25°C, unless otherwise noted.) 8 6.1 7 6 6.0 6 4 GAIN (dB) 6.2 7 5 5.9 5.8 5 4 3 5.7 3 2 5.6 2 1 5.5 1 0 5.4 0.1 1 10 FREQUENCY (MHz) 100 1000 VOUT = 2Vp-p 9 8 GAIN (dB) GAIN (dB) VOUT = 100mVp-p 6.3 10 MAX4142-02 VOUT = 100mVp-p 9 6.4 MAX4142-01 10 LARGE-SIGNAL GAIN vs. FREQUENCY GAIN FLATNESS vs. FREQUENCY MAX4142-03 SMALL-SIGNAL GAIN vs. FREQUENCY 0 0.1 1 10 FREQUENCY (MHz) 100 1000 0.1 1 10 100 1000 FREQUENCY (MHz) _______________________________________________________________________________________ 3 MAX4142 AC ELECTRICAL CHARACTERISTICS _____________________________Typical Operating Characteristics (continued) (VCC = +5V, VEE = -5V, SHDN = 0, RL = 150Ω differential, TA = +25°C, unless otherwise noted.) COMMON-MODE REJECTION vs. FREQUENCY 20 50 30 CMR (dB) 10 40 60 70 40 50 80 60 90 70 100 80 0.1 1 10 10 1 0.01 0.1 100 100 0.1 90 110 1 10 100 1000 0.1 1 10 100 FREQUENCY (MHz) FREQUENCY (MHz) FREQUENCY (MHz) VOLTAGE-NOISE DENSITY vs. FREQUENCY CURRENT-NOISE DENSITY vs. FREQUENCY HARMONIC DISTORTION vs. FREQUENCY MAX4142-09 MAX4142-08 0 RL = 150Ω VOUT = 1Vp-p -10 -20 DISTORTION (dBc) 10 100 CURRENT-NOISE DENSITY (pA/√Hz) MAX4142-07 100 VOLTAGE-NOISE DENSITY (nV/√Hz) MAX4142-05 0 30 OUTPUT IMPEDANCE vs. FREQUENCY 1000 OUTPUT IMPEDANCE (Ω) 20 PSR (dB) -10 MAX4142-04 10 MAX4142-06 POWER-SUPPLY REJECTION vs. FREQUENCY 10 -30 2nd HARMONIC -40 -50 -60 -70 3rd HARMONIC -80 1k 10k 100k 10 100 1k 10k 100k FREQUENCY (Hz) FREQUENCY (Hz) DISTORTION vs. LOAD HARMONIC DISTORTION vs. OUTPUT VOLTAGE SWING -40 -70 2nd ORDER HARMONIC -80 3rd ORDER HARMONIC -50 -100 -100 0 200 400 600 800 RESISTIVE LOAD (Ω) 1000 1200 0.010 0.005 0.000 0 2nd HARMONIC -80 -90 100 -0.005 -70 -90 0.015 3rd HARMONIC -60 DIFF. PHASE (deg) DISTORTION (dBc) -60 10 DIFFERENTIAL GAIN AND PHASE -40 -50 1 FREQUENCY (MHz) f = 5MHz RL = 150Ω -30 0.1 1M MAX4142-11 -20 MAX4142-10 fO = 5MHz, VOUT = 1Vp-p -30 1M DIFF. GAIN (%) 100 -20 4 -90 1 10 MAX4142-12 1 DISTORTION (dBc) MAX4142 250MHz, Low-Power, High-Output-Current, Differential Line Driver 100 0.010 0.005 0.000 -0.005 0 2 4 6 8 10 12 0 OUTPUT VOLTAGE SWING (Vp-p) _______________________________________________________________________________________ 100 IRE 250MHz, Low-Power, High-Output-Current, Differential Line Driver (VCC = +5V, VEE = -5V, SHDN = 0, RL = 150Ω differential, TA = +25°C, unless otherwise noted.) DIFFERENTIAL OUTPUT VOLTAGE SWING vs. TEMPERATURE 12 10 8 6 4 2 17 16 15 14 13 12 100 200 300 400 0.7 0.6 0.5 0.4 0.3 0.2 0 -45 -30 -15 500 0 15 30 45 60 75 -45 -30 -15 90 0 15 30 45 60 LOAD RESISTANCE (Ω) TEMPERATURE (°C) TEMPERATURE (°C) INPUT BIAS CURRENT vs. TEMPERATURE INPUT OFFSET CURRENT vs. TEMPERATURE POWER-SUPPLY CURRENT vs. TEMPERATURE 17 15 13 11 9 0.7 0.6 0.5 0.4 0.3 0.2 7 0.1 5 0 -45 -30 -15 0 15 30 45 60 75 SMALL-SIGNAL PULSE RESPONSE 90 14.0 13.5 13.0 12.5 12.0 11.5 11.0 10.0 0 15 30 45 60 75 90 -45 -30 -15 TEMPERATURE (°C) TEMPERATURE (°C) 75 14.5 10.5 -45 -30 -15 90 90 MAX4142-18 0.8 75 15.0 POWER-SUPPLY CURRENT (mA) 0.9 INPUT OFFSET CURRENT (µA) 19 MAX4142-17 1.0 MAX4142-16 0 0.8 0.1 0 0 15 30 45 60 TEMPERATURE (°C) LARGE-SIGNAL PULSE RESPONSE MAX4142-19 ENABLE RESPONSE TIME MAX4142-20 MAX4142-21 5V GND VOLTAGE (500mV/div) IN VOLTAGE (25mV/div) INPUT BIAS CURRENT (µA) 0.9 INPUT OFFSET VOLTAGE (mV)) 14 OUTPUT SWING (Vp-p) RL = 1MΩ DIFFERENTIAL DIFFERENTIAL OUTPUT VOLTAGE SWING (V) 16 1 MAX4142-14 18 MAX4142-13 18 INPUT OFFSET VOLTAGE vs. TEMPERATURE MAX4142-15 DIFFERENTIAL OUTPUT SWING vs. LOAD RESISTANCE GND OUT GND IN SHDN 0V 2V GND OUT VOUT 0V TIME (10ns/div) TIME (10ns/div) TIME (2µs/div) _______________________________________________________________________________________ 5 MAX4142 _____________________________Typical Operating Characteristics (continued) MAX4142 250MHz, Low-Power, High-Output-Current, Differential Line Driver _____________________Pin Description PIN NAME FUNCTION 1, 7 VEE Negative Power Supply. Connect VEE to -5V. 2 IN+ Noninverting Input 3, 5 N.C. No Connect. Not internally connected. 4 SHDN Logic Input for Shutdown Circuitry. A logic low enables the amplifier. A logic high disables the amplifier. 6 IN- Inverting Input 8, 14 VCC Positive Power Supply. Connect VCC to +5V. 9 OUT- Inverting Output 10 SENSE- 11 GND 12 SENSE+ 13 OUT+ IN+ RF Ground OUT+ SENSE+ RG VIN A3 GND ( ) R VOUT = 1 + F VIN RG RG SENSERF Inverting Output Sense. Connect to OUTclose to the pin for normal operation. A2 OUT- IN- Noninverting Output Sense. Connect to OUT+ close to the pin for normal operation. Noninverting Output Detailed Description The MAX4142 differential line driver features 250MHz bandwidth and 67dB common-mode rejection (CMR) at 10MHz. This part achieves a 1400V/µs slew rate, and power dissipation is only 125mW. The MAX4142 has an internally set +2V/V closed-loop gain, making it ideal as a back-terminated line driver. The output stage can drive ±6V into a 100Ω load. The MAX4142 utilizes a three-amplifier topology to provide differential inputs/outputs and common-mode feedback (Figure 1), making it ideal for applications with high common-mode noise, such as for driving T1 or xDSL transmissions over a twisted-pair cable. The MAX4142’s differential noninverting structure uses two noninverting amplifiers (A1 and A2) to provide a single device with differential inputs and outputs. The use of two amplifiers effectively doubles the output voltage swing and bandwidth, and improves slew rate when compared to the single op-amp differential amplifier. Excellent gain and phase, along with low noise, also make the MAX4142 suitable for video applications and RF-signal processing. For a complete differential transmission link, use the MAX4142 line driver with the MAX4144/MAX4146 line receivers, as shown in the Typical Application Circuit. 6 MAX4142 A1 Figure 1. MAX4142 Functional Diagram Applications Information Balanced Transmission Lines Differential (balanced) transmission lines use two conductors to transmit high-speed signals over low-cost cable or twisted-pair wire with minimal signal degradation. The transmit side of the balanced transmission line is driven by an amplifier with differential outputs, while the signal is received by an amplifier with differential inputs. In an ideal balanced system, each conductor has the same impedance from input to output and from the conductor to the system ground. Since the impedance from each conductor to ground is equivalent, any noise or other interference coupled into the transmission line will be equal in magnitude in each conductor, appearing as a common-mode signal to the amplifier at the receiving end of the transmission line. Since the receiving amplifier subtracts the signals on each side of the transmission line to obtain the desired information, common-mode signals are effectively canceled out by the receiving amplifier. Common-Mode Feedback In nonideal balanced systems, impedance mismatches between the conductors of a transmission line can degrade system common-mode rejection (CMR) by converting a portion of any common-mode signal to a _______________________________________________________________________________________ 250MHz, Low-Power, High-Output-Current, Differential Line Driver IN+ MAX4142 A1 RF RF • High-frequency design techniques must be followed when designing the PC board for the MAX4142. • Use surface-mount power-supply bypass capacitors instead of through-hole capacitors. Their shorter lead lengths reduce parasitic inductance, leading to superior high-frequency performance. • Keep signal lines as short and as straight as possible. Do not make 90° turns; round all corners. • The ground plane should be as free from voids as possible. A differential input voltage as high as 10V will cause only 2.1mA to flow—much less than the 10mA absolute maximum rating. OUT- A2 IN- Figure 2. MAX4142 Input Protection Circuit IN- MAX4142 OUT700Ω Input Stage Circuitry The MAX4142 includes internal protection circuitry that prevents damage to the precision input stage from large differential input voltages. This protection circuitry consists of five back-to-back Schottky protection diodes between IN+ and R G, and IN- and RG (Figure 2). The diodes limit the differential voltage applied to the amplifiers’ internal circuitry to no more than 10VF, where VF is the diode’s forward voltage drop (about 0.4V at +25°C). For a large differential input voltage (exceeding 4V), the MAX4142 input bias current (at IN+ and IN-) increases according to the following equation: Input current = [(VIN+ - VIN-) - 10VF] / 1.4kΩ SENSE+ SENSE- Observe the following guidelines when designing your PC board: • Do not use wire-wrap boards; they are too inductive. • Do not use IC sockets; they increase parasitic capacitance and inductance. OUT+ 2RG Grounding, Bypassing, and PC Board Layout • The printed circuit board should have at least two layers: the signal layer and the ground plane. MAX4142 differential signal that is amplified by the receiver. The unique topology of the MAX4142 (Figure 1) utilizes two amplifiers (A1 and A2) to provide differential inputs and outputs, and a third amplifier (A3) to provide commonmode feedback. The common-mode feedback amplifier senses common-mode voltage at the MAX4142 output and forces this voltage to zero, effectively removing common-mode voltages from the transmission line. This technique improves CMR for systems with imperfectly balanced transmission-line impedances. 1.4k OUT+ 700Ω IN+ Figure 3. MAX4142 Shutdown Equivalent Circuit Shutdown Mode The MAX4142 can be put into low-power shutdown mode by driving SHDN high. The amplifier output is high impedance in this mode; thus the impedance at OUT is that of the feedback resistors (2.8kΩ) (Figure 3). _______________________________________________________________________________________ 7 MAX4142 250MHz, Low-Power, High-Output-Current, Differential Line Driver 5 IN+ MAX4142 A1 4 OUT+ 3 GAIN (dB) 2 RF SENSE+ RG RL CL = 5pF CL = 10pF -3 -4 RG -5 SENSE- 100k RF 1M 10M 100M 1G FREQUENCY (Hz) OUT- A2 Figure 5. MAX4142 Small-Signal Response with Capacitive Load IN- Figure 4. Connection of SENSE+ and SENSE- to a Remote Load Using SENSE+ and SENSEThe MAX4142 has two output voltage-sense pins, SENSE+ and SENSE-. These pins are normally connected to the MAX4142’S OUT+ and OUT- pins. In some long-line applications, it may be desirable to connect SENSE+ to OUT+ and SENSE- to OUT- at the load, instead of the typical connection at the part (Figure 4). This compensates for the long line’s resistance, which otherwise leads to an IR voltage error. When using this technique, keep the sense lines’ impedance low to minimize gain errors. Also, keep capacitance low to maximize frequency response. The gain of the MAX4142 is approximated by the following equation: ( ) ( RF + ∆RSENSE + + ∆RSENSE − AV = 1 + RG ) where ∆RSENSE+ and ∆RSENSE- are the SENSE+ and SENSE- trace impedances, respectively. For the MAX4142, RF is 700Ω and RG is 700Ω. Additionally, mismatches in the SENSE+ and SENSEtraces lead to common-mode gain errors. However, these errors are effectively eliminated by the MAX4142’s common-mode feedback (see the Common-Mode Feedback section). 8 0 -1 -2 GND A3 CL = 15pF 1 Driving Capacitive Loads The MAX4142 provides maximum AC performance when driving no output load capacitance. This is the case when driving a correctly terminated transmission line (i.e., a back-terminated cable). In most amplifier circuits, driving large-load capacitance increases the chance of oscillations. The amplifier’s output impedance and the load capacitor combine to add a pole and excess phase to the loop response. If the pole’s frequency is low enough and phase margin is degraded sufficiently, oscillations may occur. A second concern when driving capacitive loads results from the amplifier’s output impedance, which looks inductive at high frequencies. The inductance forms an L-C resonant circuit with the capacitive load. This causes peaking in the frequency response and degrades the amplifier’s phase margin. The MAX4142 drives capacitive loads up to 25pF without oscillation. However, some peaking may occur in the frequency domain (Figure 5). To drive larger-capacitance loads or to reduce ringing, add isolation resistors between the amplifier’s outputs and the load (Figure 6). The value of R ISO depends on the capacitive load (Figure 7). With higher capacitive values, bandwidth is dominated by the RC network formed by RISO and CL; the bandwidth of the amplifier itself is much higher. Also note that the isolation resistor forms a divider that decreases the voltage delivered to the load. _______________________________________________________________________________________ 250MHz, Low-Power, High-Output-Current, Differential Line Driver MAX4142 25 MAX4142 A1 RL = 150Ω OUT+ RISO CLOAD RF RLOAD SENSE+ RG A3 GND ISOLATION RESISTANCE (Ω) IN+ 20 15 10 5 RG 0 SENSE- 0 RF A2 IN- 50 100 150 200 250 300 350 400 450 500 CAPACITIVE LOAD (pF) OUTRISO Figure 7. Isolation Resistance vs. Capacitive Load CLOAD RLOAD Figure 6. Addition of RISO to Amplifier Output ___________________Chip Information TRANSISTOR COUNT: 243 SUBSTRATE CONNECTED TO VEE _______________________________________________________________________________________ 9 ________________________________________________________Package Information SOICN.EPS MAX4142 250MHz, Low-Power, High-Output-Current, Differential Line Driver 10 ______________________________________________________________________________________ 250MHz, Low-Power, High-Output-Current, Differential Line Driver ______________________________________________________________________________________ MAX4142 NOTES 11 MAX4142 250MHz, Low-Power, High-Output-Current, Differential Line Driver NOTES 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. 12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.