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19-4763; Rev 0; 7/98
KIT ATION EVALU ABLE AVAIL
250MHz, Low-Power, High-Output-Current, Differential Line Driver
General Description ____________________________Features
o 250MHz -3dB Bandwidth (AV = +2V/V) o 1400V/s Slew Rate o 67dB at 10MHz CMR o 0.01%/0.01 Differential Gain/Phase o 6V Differentially into 100 Output Drive o 1mA Shutdown Capability o 12.5mA Quiescent Supply Current o Available in 14-Pin Narrow SO Package
MAX4142
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/s 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 100 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.
Ordering Information
PART MAX4142ESD TEMP. RANGE -40C to +85C PIN-PACKAGE 14 SO
Pin Configuration
TOP VIEW
VEE 1 IN+ 2 N.C. 3 14 VCC
________________________Applications
Video Twisted-Pair Driver Differential Pulse Amplifier High-Speed Instrumentation Amplifier Low-Noise Differential Receivers Differential ADC Driver
MAX4142
13 OUT+ 12 SENSE+ 11 GND 10 SENSE9 8 OUTVCC
SHDN 4 N.C. 5 IN- 6 VEE 7
SO
N.C. = NOT INTERNALLY CONNECTED
Typical Application Circuit
IN+
SENSE+ OUT+
Rt
Rt SENSE IN75 75 COAX VOUT OUT 75
MAX4142
INSENSE-
GND OUTIN+ Rt
MAX4144
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.
250MHz, Low-Power, High-Output-Current, Differential Line Driver MAX4142
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 = +70C) Plastic SO (derate 8.3mW/C above +70C) ................667mW Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10sec) .............................+300C
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 = +25C.) , PARAMETER Operating Supply Voltage Input Offset Voltage Input Offset Voltage Drift Input Bias Current Input Offset Current Input Capacitance Differential Input Resistance Differential Input Voltage Range Common-Mode Input Voltage Range Gain Gain Error Gain Drift Common-Mode Rejection Power-Supply Rejection Quiescent Supply Current Shutdown Supply Current CMR PSR ICC, IEE ICC, SHDN VCM AV VOS TCVOS IB IOS CIN RIN Guaranteed by output voltage swing test Guaranteed by CMR test -1V VOUT 1V, RL = 53 -1V VOUT 1V, RL = 53 RL = 53 VCM = 1.7V VS = 4.5V to 5.5V VIN = 0 VSHDN 2V, VIN = 0 Single-ended, RL = Output Voltage Swing 3.0 6.0 2.0 4.0 120 Differential, RL = Single-ended, RL = 26.5 Differential, RL = 53 Output Current Drive Output Resistance SHDN Logic-High Threshold SHDN Logic-Low Threshold Enable Time from Shutdown Disable Time to Shutdown SHDN Input Current IOUT ROUT VIH VIL tON tOFF ISHDN VSHDN = 0 0.8 500 3.5 66 150 RL = 20 55 65 -3.0 -1.7 2 0.3 20 80 95 12.5 1.0 3.4 6.8 2.4 4.8 75 0.1 2.0 mA V V ns s A V 18 2.0 2 SYMBOL VIN = 0 VIN = 0 VIN = 0 VIN = 0 CONDITIONS Guaranteed by PSR test MIN 4.5 0.4 3 10 0.2 1 1 3.0 1.7 25 2.5 TYP MAX 5.5 8 UNITS V mV V/C A A pF M V V V/V % ppm/C dB dB mA mA
VOUT
2
_______________________________________________________________________________________
250MHz, Low-Power, High-Output-Current, Differential Line Driver
AC ELECTRICAL CHARACTERISTICS
(VCC = +5V, VEE = -5V, SHDN = 0V, RL = 150 differential, CONDITIONSTMAX, unless otherwise noted. Typical values specified at TA = TMIN to PARAMETER SYMBOL MIN TYP MAX UNITS T-3dB+25C.) A = Bandwidth BW(-3dB) VOUT 0.1VRMS 250 MHz Full-Power Bandwidth FPBW VOUT = 2Vp-p 180 MHz 0.1dB Bandwidth Common-Mode Rejection Slew Rate Settling Time Differential Gain Differential Phase Input Voltage Noise Input Current Noise Spurious-Free Dynamic Range BW(0.1dB) CMR SR tS DG DP en in SFDR VOUT 0.1VRMS f = 10MHz, VCM = 2V Differential, -2V VOUT +2V -1V VOUT +1V f = 3.58MHz f = 3.58MHz f = 10kHz f = 1MHz to 100MHz f = 10kHz f = 1MHz to 100MHz fC = 500kHz, VOUT = 1Vp-p, RS = 50, Figure1 fC = 10MHz, VOUT = 1Vp-p, RS = 50, Figure1 to 0.1% to 0.01% 70 67 1400 25 45 0.01 0.01 8 80 2 20 -84 -76 MHz dB V/s ns % degrees nV/Hz VRMS pAHz nARMS dBc
MAX4142
__________________________________________Typical Operating Characteristics
(VCC = +5V, VEE = -5V, SHDN = 0, RL = 150 differential, TA = +25C, unless otherwise noted.)
SMALL-SIGNAL GAIN vs. FREQUENCY
MAX4142-01
GAIN FLATNESS vs. FREQUENCY
MAX4142-02
LARGE-SIGNAL GAIN vs. FREQUENCY
9 8 7 GAIN (dB) 6 5 4 3 2 1 0 VOUT = 2Vp-p
MAX4142-03
10 9 8 7 GAIN (dB) VOUT = 100mVp-p
6.4 6.3 6.2 6.1 GAIN (dB) 6.0 5.9 5.8 5.7 5.6 5.5 5.4 VOUT = 100mVp-p
10
6 5 4 3 2 1 0 0.1 1 10 FREQUENCY (MHz) 100 1000
0.1
1
10 FREQUENCY (MHz)
100
1000
0.1
1
10 FREQUENCY (MHz)
100
1000
_______________________________________________________________________________________
3
250MHz, Low-Power, High-Output-Current, Differential Line Driver MAX4142
_____________________________Typical Operating Characteristics (continued)
(VCC = +5V, VEE = -5V, SHDN = 0, RL = 150 differential, TA = +25C, unless otherwise noted.)
POWER-SUPPLY REJECTION vs. FREQUENCY
MAX4142-04
COMMON-MODE REJECTION vs. FREQUENCY
MAX4142-05
OUTPUT IMPEDANCE vs. FREQUENCY
MAX4142-06
10 20 30 40
-10 0 10 20 CMR (dB) 30 40 50 60 70 80 90
1000
PSR (dB)
50 60 70 80 90 100 110 0.1 1 10 FREQUENCY (MHz) 100
OUTPUT IMPEDANCE () 0.1 1 10 FREQUENCY (MHz) 100 1000
100
10
1
0.1
0.01 0.1 1 10 FREQUENCY (MHz) 100
VOLTAGE-NOISE DENSITY vs. FREQUENCY
MAX4142-07
CURRENT-NOISE DENSITY vs. FREQUENCY
MAX4142-08
HARMONIC DISTORTION vs. FREQUENCY
-10 -20 DISTORTION (dBc) -30 -40 -50 -60 -70 -80 3rd HARMONIC 0.1 1 10 100 2nd HARMONIC RL = 150 VOUT = 1Vp-p
MAX4142-09
100 VOLTAGE-NOISE DENSITY (nV/Hz)
100 CURRENT-NOISE DENSITY (pA/Hz)
0
10
10
1 10 100 1k 10k 100k 1M FREQUENCY (Hz)
1 10 100 1k 10k 100k 1M FREQUENCY (Hz)
-90 FREQUENCY (MHz)
DISTORTION vs. LOAD
MAX4142-10
HARMONIC DISTORTION vs. OUTPUT VOLTAGE SWING
MAX4142-11
DIFFERENTIAL GAIN AND PHASE
DIFF. GAIN (%) 0.010 0.005 0.000 -0.005 0 DIFF. PHASE (deg) 100
MAX4142-12
-20 -30 -40 DISTORTION (dBc) -50 -60 -70 -80 -90 -100 0 200 400 600 800 1000 2nd ORDER HARMONIC fO = 5MHz, VOUT = 1Vp-p
-20 -30 -40 DISTORTION (dBc) -50 -60 -70 -80 -90 -100 0
0.015
f = 5MHz RL = 150
3rd HARMONIC 0.010 0.005 0.000 -0.005 2 4 6 8 10 12 2nd HARMONIC
3rd ORDER HARMONIC
1200
0 IRE
100
RESISTIVE LOAD ()
OUTPUT VOLTAGE SWING (Vp-p)
4
_______________________________________________________________________________________
250MHz, Low-Power, High-Output-Current, Differential Line Driver
_____________________________Typical Operating Characteristics (continued)
(VCC = +5V, VEE = -5V, SHDN = 0, RL = 150 differential, TA = +25C, unless otherwise noted.)
DIFFERENTIAL OUTPUT SWING vs. LOAD RESISTANCE
MAX4142-13
MAX4142
DIFFERENTIAL OUTPUT VOLTAGE SWING vs. TEMPERATURE
MAX4142-14
INPUT OFFSET VOLTAGE vs. TEMPERATURE
0.9 INPUT OFFSET VOLTAGE (mV)) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1
MAX4142-15
18 16 OUTPUT SWING (Vp-p) 14 12 10 8 6 4 2 0 0 100 200 300 400
18 DIFFERENTIAL OUTPUT VOLTAGE SWING (V) RL = 1M DIFFERENTIAL 17 16 15 14 13 12
1
0 -45 -30 -15 0 15 30 45 60 75 90 -45 -30 -15 0 15 30 45 60 75 90 TEMPERATURE (C) TEMPERATURE (C)
500
LOAD RESISTANCE ()
INPUT BIAS CURRENT vs. TEMPERATURE
19 INPUT BIAS CURRENT (A) 17 15 13 11 9 7 5 -45 -30 -15 0 15 30 45 60 75 90 TEMPERATURE (C)
MAX4142-16
INPUT OFFSET CURRENT vs. TEMPERATURE
MAX4142-17
POWER-SUPPLY CURRENT vs. TEMPERATURE
14.5 POWER-SUPPLY CURRENT (mA) 14.0 13.5 13.0 12.5 12.0 11.5 11.0 10.5 10.0
MAX4142-18
1.0 0.9 INPUT OFFSET CURRENT (A) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 -45 -30 -15 0 15 30 45 60 75
15.0
90
-45 -30 -15
0
15
30
45
60
75
90
TEMPERATURE (C)
TEMPERATURE (C)
SMALL-SIGNAL PULSE RESPONSE
MAX4142-19
LARGE-SIGNAL PULSE RESPONSE
MAX4142-20
ENABLE RESPONSE TIME
MAX4142-21
5V VOLTAGE (500mV/div) IN VOLTAGE (25mV/div) GND IN GND SHDN 0V
2V OUT GND VOUT 0V
OUT
GND
TIME (10ns/div)
TIME (10ns/div)
TIME (2s/div)
_______________________________________________________________________________________
5
250MHz, Low-Power, High-Output-Current, Differential Line Driver MAX4142
_____________________Pin Description
PIN 1, 7 2 3, 5 4 6 8, 14 9 10 11 12 13 NAME VEE IN+ N.C. SHDN INVCC OUTSENSEGND SENSE+ OUT+ FUNCTION
IN+
Negative Power Supply. Connect VEE to -5V. Noninverting Input No Connect. Not internally connected. Logic Input for Shutdown Circuitry. A logic low enables the amplifier. A logic high disables the amplifier. Inverting Input Positive Power Supply. Connect VCC to +5V. Inverting Output Inverting Output Sense. Connect to OUTclose to the pin for normal operation. Ground Noninverting Output Sense. Connect to OUT+ close to the pin for normal operation. Noninverting Output
VIN RG RG
MAX4142
A1
OUT+
RF
SENSE+
A3
GND
R VOUT = 1 + F VIN RG
()
SENSERF OUT-
A2 IN-
Figure 1. MAX4142 Functional Diagram
Detailed Description
The MAX4142 differential line driver features 250MHz bandwidth and 67dB common-mode rejection (CMR) at 10MHz. This part achieves a 1400V/s 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 100 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.
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
6
_______________________________________________________________________________________
250MHz, Low-Power, High-Output-Current, Differential Line Driver
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.
MAX4142
IN+ A1
MAX4142
OUT+
RF
SENSE+
2RG SENSERF
Grounding, Bypassing, and PC Board Layout
Observe the following guidelines when designing your PC board: * High-frequency design techniques must be followed when designing the PC board for the MAX4142. * The printed circuit board should have at least two layers: the signal layer and the ground plane. * Do not use wire-wrap boards; they are too inductive. * Do not use IC sockets; they increase parasitic capacitance and inductance. * 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.
IN-
A2
OUT-
Figure 2. MAX4142 Input Protection Circuit
IN-
MAX4142
OUT700 1.4k
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 +25C). 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] / 1.4k A differential input voltage as high as 10V will cause only 2.1mA to flow--much less than the 10mA absolute maximum rating.
700
OUT+
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 (2.8k) (Figure 3).
7
_______________________________________________________________________________________
250MHz, Low-Power, High-Output-Current, Differential Line Driver MAX4142
IN+ A1 5
MAX4142
OUT+
4 3 2 CL = 15pF
SENSE+
GAIN (dB)
RF
1 0 -1 -2 CL = 5pF CL = 10pF
RG A3 RG SENSERF OUTGND RL
-3 -4 -5 100k 1M 10M FREQUENCY (Hz) 100M 1G
A2 IN-
Figure 5. MAX4142 Small-Signal Response with Capacitive Load
Figure 4. Connection of SENSE+ and SENSE- to a Remote Load
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.
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 SENSE+ and SENSE- are the SENSE+ and R R SENSE- trace impedances, respectively. For the MAX4142, RF is 700 and RG is 700. 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
_______________________________________________________________________________________
250MHz, Low-Power, High-Output-Current, Differential Line Driver MAX4142
IN+ A1 25
MAX4142
RL = 150 OUT+ RISO CLOAD SENSE+ RLOAD ISOLATION RESISTANCE () 20
RF
15
RG A3 RG SENSERF OUTRISO CLOAD RLOAD GND
10
5
0 0 50 100 150 200 250 300 350 400 450 500 CAPACITIVE LOAD (pF)
A2 IN-
Figure 7. Isolation Resistance vs. Capacitive Load
Figure 6. Addition of RISO to Amplifier Output
___________________Chip Information
TRANSISTOR COUNT: 243 SUBSTRATE CONNECTED TO VEE
_______________________________________________________________________________________
9
250MHz, Low-Power, High-Output-Current, Differential Line Driver MAX4142
________________________________________________________Package Information
SOICN.EPS
10
______________________________________________________________________________________
250MHz, Low-Power, High-Output-Current, Differential Line Driver
NOTES
MAX4142
11
______________________________________________________________________________________
250MHz, Low-Power, High-Output-Current, Differential Line Driver MAX4142
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 (c) 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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