19-1284; Rev 0; 10/97 Low-Cost, High-Speed, Single-Supply, Gain of +2 Buffers with Rail-to-Rail Outputs in SOT23 The MAX4014/MAX4017/MAX4019/MAX4022 are precision, closed-loop, gain of +2 (or -1) buffers featuring high slew rates, high output current drive, and low differential gain and phase errors. These single-supply devices operate from +3.15V to +11V, or from ±1.575V to ±5.5V dual supplies. The input voltage range extends 100mV beyond the negative supply rail and the outputs swing Rail-to-Rail®. These devices require only 5.5mA of quiescent supply current while achieving a 200MHz -3dB bandwidth and a 600V/µs slew rate. In addition, the MAX4019 has a disable feature that reduces the supply current to 400µA. Input voltage noise for these parts is only 10nV/√Hz and input current noise is only 1.3pA/√Hz. This buffer family is ideal for low-power/low-voltage applications that require wide bandwidth, such as video, communications, and instrumentation systems. For space-sensitive applications, the MAX4014 comes in a tiny 5-pin SOT23 package. ____________________________Features ♦ Internal Precision Resistors for Closed-Loop Gains of +2 or -1 ♦ High Speed: 200MHz -3dB Bandwidth 30MHz 0.1dB Gain Flatness (6MHz min) 600V/µs Slew Rate ♦ Single 3.3V/5.0V Operation ♦ Outputs Swing Rail-to-Rail ♦ Input Voltage Range Extends Beyond VEE ♦ Low Differential Gain/Phase: 0.04%/0.02° ♦ Low Distortion at 5MHz: -78dBc Spurious-Free Dynamic Range -75dB Total Harmonic Distortion ♦ High Output Drive: ±120mA ♦ Low, 5.5mA Supply Current ♦ 400µA Shutdown Supply Current ♦ Space-Saving SOT23-5, µMAX, or QSOP Packages _____________________Selector Guide PART NO. OF AMPS ENABLE MAX4014 1 No 5-Pin SOT23 MAX4017 2 No 8-Pin SO/µMAX PIN-PACKAGE ______________Ordering Information PART TEMP. RANGE PINPACKAGE SOT TOP MARK MAX4014EUK -40°C to +85°C 5 SOT23-5 ABZQ MAX4017ESA -40°C to +85°C 8 SO — -40°C to +85°C 8 µMAX — MAX4019 3 Yes 14-Pin SO, 16-Pin QSOP MAX4017EUA MAX4019ESD -40°C to +85°C 14 SO — MAX4022 4 No 14-Pin SO, 16-Pin QSOP MAX4019EEE -40°C to +85°C 16 QSOP — MAX4022ESD -40°C to +85°C 14 SO — MAX4022EEE -40°C to +85°C 16 QSOP — ________________________Applications __________Typical Operating Circuit Portable/Battery-Powered Instruments Video Line Driver IN+ 75Ω Analog-to-Digital Converter Interface VOUT CCD Imaging Systems 75Ω Video Routing and Switching Systems MAX4014 IN- Rail-to-Rail is a registered trademark of Nippon Motorola Ltd. 500Ω 500Ω GAIN OF +2 VIDEO/RF CABLE DRIVER ________________________________________________________________ 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. MAX4014/MAX4017/MAX4019/MAX4022 _______________General Description MAX4014/MAX4017/MAX4019/MAX4022 Low-Cost, High-Speed, Single-Supply, Gain of +2 Buffers with Rail-to-Rail Outputs in SOT23 ABSOLUTE MAXIMUM RATINGS Supply Voltage (VCC to VEE) ..................................................12V IN_-, IN_+, OUT_, EN_ ....................(VEE - 0.3V) to (VCC + 0.3V) Output Short-Circuit Duration to VCC or VEE ..............Continuous Continuous Power Dissipation (TA = +70°C) 5-pin SOT23 (derate 7.1mW/°C above+70°C)..............571mW 8-pin SO (derate 5.9mW/°C above +70°C)...................471mW 8-pin µMAX (derate 4.1mW/°C above +70°C) ..............330mW 14-pin SO (derate 8.3mW/°C above +70°C).................667mW 16-pin QSOP (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 at 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 = 0V, IN_- =0V, EN_ = 5V, RL = ∞ to ground, VOUT = VCC / 2, noninverting configuration, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER Input Voltage Range Input Offset Voltage Input Offset Voltage Drift SYMBOL VIN VOS Input Resistance Voltage Gain IB VEE - 0.1 VCC + 0.1 RL = 50Ω 4 ±1 mV IN_+ (Note 2) 5.4 AV RL ≥ 50Ω, (VEE + 0.5V) ≤ VOUT ≤ (VCC - 2.0V) Output Current IOUT RL = 20Ω to VCC or VEE RL =150Ω RL = 2kΩ 1.9 ±80 Disabled Output Resistance µA MΩ 2.1 25 V/V mΩ ±120 mA 2 ±150 1.60 2.00 VOL - VEE 0.04 0.50 VCC - VOH 0.75 1.50 VOL - VEE 0.04 0.50 VCC - VOH 0.06 VOL - VEE 46 57 VCC = 5V, VEE = -5V, VOUT = 0V 54 66 VCC to VEE MAX4019 EN_ Logic-High Threshold VIH MAX4019 dB 45 3.15 ROUT(OFF) MAX4019, EN_ = 0V, 0V ≤ VOUT ≤ 5V VIL 11.0 1 VCC - 2.6 VCC - 1.5 0.5 EN_ = VEE 200 MAX4019 EN_ Logic Input High Current IIH MAX4019, EN_ = VCC 0.5 10 Enabled (EN_ = VCC) 5.5 8.0 MAX4019, disabled (EN_ = VEE) 0.4 0.7 2 V V (VEE + 0.2V) ≤ EN_ ≤ VCC IIL ICC V kΩ EN_ Logic Input Low Current Quiescent Supply Current (per Buffer) V 0.06 VCC = 5V, VEE = 0V, VOUT = 2V EN_ Logic-Low Threshold mA VCC - VOH VCC = 3.3V, VEE = 0V, VOUT = 0.9V Operating Supply-Voltage Range 20 3 Sinking or sourcing RL = 50Ω PSRR mV Any channels for MAX4017/MAX4019/MAX4022 f = DC Power-Supply Rejection Ratio (Note 3) V µV/°C IN_+, over input voltage range VOUT 20 UNITS 8 ROUT Output Voltage Swing MAX IN_- RIN ISC TYP VCC - 2.25 Output Resistance Short-Circuit Output Current MIN VEE - 0.1 TCVOS Input Offset Voltage Matching Input Bias Current CONDITIONS IN_+ _______________________________________________________________________________________ 550 µA µA mA Low-Cost, High-Speed, Single-Supply, Gain of +2 Buffers with Rail-to-Rail Outputs in SOT23 (VCC = +5V, VEE = 0V, IN_- = 0V, EN_ = 5V, RL = 100Ω to ground, noninverting configuration, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL Small-Signal -3dB Bandwidth BWSS VOUT = 20mVp-p 200 MHz Large-Signal -3dB Bandwidth BWLS VOUT = 2Vp-p 140 MHz 30 MHz Bandwidth for 0.1dB Gain Flatness BW0.1dB CONDITIONS VOUT = 20mVp-p (Note 4) MIN 6 TYP MAX UNITS Slew Rate SR VOUT = 2V step 600 V/µs Settling Time to 0.1% tS VOUT = 2V step 45 ns 1 ns -78 dBc Rise/Fall Time tR, tF VOUT = 100mVp-p Spurious-Free Dynamic Range SFDR fC = 5MHz, VOUT = 2Vp-p Harmonic Distortion Third-Order Intercept HD IP3 Input 1dB Compression Point VOUT = 2Vp-p, fC = 5MHz Second harmonic -78 Third harmonic -82 Total harmonic distortion -75 dBc f = 10.0MHz 35 fC = 10MHz, AVCL = +2V/V 11 dBm dBm degrees Differential Phase Error DP NTSC, RL = 150Ω 0.02 Differential Gain Error DG NTSC, RL = 150Ω 0.04 % Input Noise Voltage Density en f = 10kHz 10 nV/√Hz Input Noise Current Density in f = 10kHz 1.3 pA/√Hz Input Capacitance CIN Disabled Output Capacitance COUT(OFF) 1 pF MAX4019, EN_ = 0V 2 pF Output Impedance ZOUT f = 10MHz 6 Ω Buffer Enable Time tON MAX4019 100 ns Buffer Disable Time tOFF MAX4019 Buffer Gain Matching Buffer Crosstalk XTALK 1 µs MAX4017/MAX4019/MAX4022, f = 10MHz, VOUT = 20mVp-p 0.1 dB MAX4017/MAX4019/MAX4022, f = 10MHz, VOUT = 2Vp-p -95 dB Note 1: The MAX4014EUK is 100% production tested at TA = +25°C. Specifications over temperature limits are guaranteed by design. Note 2: Tested with VOUT = +2.5V. Note 3: PSRR for single +5V supply tested with VEE = 0V, VCC = +4.5V to +5.5V; for dual ±5V supply with VEE = -4.5V to -5.5V, VCC = +4.5V to +5.5V; and for single +3V supply with VEE = 0V, VCC = +3.15V to +3.45V. Note 4: Guaranteed by design. _______________________________________________________________________________________ 3 MAX4014/MAX4017/MAX4019/MAX4022 AC ELECTRICAL CHARACTERISTICS __________________________________________Typical Operating Characteristics (VCC = +5V, VEE = 0V, AVCL = +2, RL = 150Ω to VCC / 2, TA = +25°C, unless otherwise noted.) GAIN FLATNESS vs. FREQUENCY 8 MAX4014-02 MAX4014-01 7 LARGE-SIGNAL GAIN vs. FREQUENCY 6.8 6.7 7 6.6 6 5 4 GAIN (dB) 6.5 GAIN (dB) 6.4 6.3 2 6.0 1 1M 10M 100M 0 100k 1G 1M 10M 100M 1G 100k 10M 100M FREQUENCY (Hz) FREQUENCY (Hz) MAX4017/19/22 CROSSTALK vs. FREQUENCY CLOSED-LOOP OUTPUT IMPEDANCE vs. FREQUENCY HARMONIC DISTORTION vs. FREQUENCY 10 100 IMPEDANCE (Ω) -10 -30 -50 -70 -90 10 1 -110 0 -10 HARMONIC DISTORTION (dBc) 30 1G MAX4014-06 1000 MAX4014-04 50 VOUT = 2Vp-p -20 -30 -40 -50 -60 2ND HARMONIC -70 -80 3RD HARMONIC -90 -130 0.1 -150 1M 10M 100M 10M 100M 1M 10M 100M FREQUENCY (Hz) HARMONIC DISTORTION vs. LOAD HARMONIC DISTORTION vs. OUTPUT SWING MAX4019 OFF ISOLATION vs. FREQUENCY -50 -60 2rd HARMONIC -80 3rd HARMONIC -30 -40 -50 -60 -70 2ND HARMONIC -80 400 600 LOAD (Ω) 800 1000 -20 -30 -40 -50 -60 -70 3RD HARMONIC -80 -90 -100 200 0 -10 -20 -90 -100 10 OFF ISOLATION (dB) -40 f = 5MHz -10 HARMONIC DISTORTION (dBc) -30 -70 0 MAX4014-07 -20 0 100k FREQUENCY (Hz) f = 5MHz VOUT = 2Vp-p -90 1M FREQUENCY (Hz) 0 -10 -100 0.1M 1G MAX4014-08 100k 4 1M FREQUENCY (Hz) MAX4014-05 100k CROSSTALK (dB) 6.1 5.9 1 4 3 6.2 3 2 5 MAX4014-09 GAIN (dB) 6 MAX4014-03 SMALL-SIGNAL GAIN vs. FREQUENCY 8 HARMONIC DISTORTION (dBc) MAX4014/MAX4017/MAX4019/MAX4022 Low-Cost, High-Speed, Single-Supply, Gain of +2 Buffers with Rail-to-Rail Outputs in SOT23 0.5 1.0 1.5 OUTPUT SWING (Vp-p) 2.0 100k 1M 10M FREQUENCY (Hz) _______________________________________________________________________________________ 100M Low-Cost, High-Speed, Single-Supply, Gain of +2 Buffers with Rail-to-Rail Outputs in SOT23 POWER-SUPPLY REJECTION vs. FREQUENCY VOLTAGE NOISE DENSITY vs. FREQUENCY MAX4014-12 100 MAX4014-11 10 0 -10 -20 -30 -40 NOISE (nV/√Hz) NOISE (pA/ √Hz) POWER-SUPPLY REJECTION (dB) 10 MAX4014-10 20 CURRENT NOISE DENSITY vs. FREQUENCY 10 -50 -60 -70 -80 1 1M 10M 100M 10 100 1k 10k 100k 1M 10M 1 OUTPUT SWING vs. LOAD RESISTANCE (RL) BANDWIDTH vs. LOAD RESISTANCE 400 350 3.0 2.5 2.0 10k 100k 1M 0 25 50 POWER-SUPPLY CURRENT (PER AMPLIFIER) vs. TEMPERATURE 3 MAX4014-17 5.5 5.0 4.5 75 100 200 300 400 500 LOAD RESISTANCE (Ω) 600 0.16 0.12 0.08 0.04 0 4.0 0 25 50 TEMPERATURE (°C) 100 0.20 INPUT OFFSET CURRENT (µA) 4 0 150 INPUT OFFSET CURRENT vs. TEMPERATURE 6.0 INPUT BIAS CURRENT (µA) 5 75 100 125 LOAD RESISTANCE (Ω) INPUT BIAS CURRENT vs. TEMPERATURE MAX4014-16 6 150 50 LOAD RESISTANCE (Ω) 7 200 MAX4014-18 1k 250 100 1.0 100 10M 300 3.5 BANDWIDTH (MHz) OUTPUT SWING (Vp-p) 4.0 1M MAX4014-15 MAX4014-13 4.5 2 POWER-SUPPLY CURRENT (mA) 10k 100k OUTPUT SWING vs. LOAD RESISTANCE 1.5 -25 1k FREQUENCY (Hz) 3 -50 100 FREQUENCY (Hz) 4 10 10 FREQUENCY (Hz) 5 OUTPUT SWING (Vp-p) 1 1 MAX4014-14 100k -50 -25 0 25 50 TEMPERATURE (°C) 75 100 -50 -25 0 25 50 TEMPERATURE (°C) 75 _______________________________________________________________________________________ 100 5 MAX4014/MAX4017/MAX4019/MAX4022 __________________________________________Typical Operating Characteristics (VCC = +5V, VEE = 0V, AVCL = +2, RL = 150Ω to VCC / 2, TA = +25°C, unless otherwise noted.) __________________________________________Typical Operating Characteristics (VCC = +5V, VEE = 0V, AVCL = +2, RL = 150Ω to VCC / 2, TA = +25°C, unless otherwise noted.) 4 2 0 4 3 2 4 5 6 7 8 9 10 POWER-SUPPLY VOLTAGE (V) 11 4.4 4.0 -50 DIFFERENTIAL GAIN AND PHASE -25 0 25 50 TEMPERATURE (°C) 75 -50 100 -25 0 25 50 TEMPERATURE (°C) 75 100 SMALL-SIGNAL PULSE RESPONSE (CL = 5pF) SMALL-SIGNAL PULSE RESPONSE MAX4014-23 MAX4014-24 0.01 0.00 -0.01 -0.02 -0.03 -0.04 -0.05 MAX4014-22 IN 0 100 IRE 0.010 0.005 0.000 -0.005 -0.010 -0.015 -0.020 -0.025 0 VOLTAGE (25mV/div) IN VOLTAGE (25mV/div) DIFF. GAIN (%) 4.6 4.2 1 0 3 DIFF. PHASE (deg) RL = 150Ω TO VCC / 2 4.8 VOLTAGE SWING (Vp-p) 6 5.0 MAX4014-20 MAX4014-19 8 VOLTAGE SWING vs. TEMPERATURE 5 INPUT OFFSET VOLTAGE (mV) POWER-SUPPLY CURRENT (mA) 10 INPUT OFFSET VOLTAGE vs. TEMPERATURE MAX4014-21 POWER-SUPPLY CURRENT (PER AMPLIFIER) vs. POWER-SUPPLY VOLTAGE OUT OUT TIME (20ns/div) TIME (20ns/div) 100 VCM = 1.25V, RL = 100Ω to GROUND IRE LARGE-SIGNAL PULSE RESPONSE (CL = 5pF) LARGE-SIGNAL PULSE RESPONSE MAX4014-25 ENABLE RESPONSE TIME MAX4014-27 MAX4014-26 5.0V (ENABLE) IN EN_ VOLTAGE (500mV/div) VOLTAGE (500mV/div) MAX4014/MAX4017/MAX4019/MAX4022 Low-Cost, High-Speed, Single-Supply, Gain of +2 Buffers with Rail-to-Rail Outputs in SOT23 OUT IN 0V (DISABLE) 1V OUT OUT 0V TIME (20ns/div) VCM = 0.9V, RL = 100Ω to GROUND 6 TIME (1µs/div) TIME (20ns/div) VCM = 1.75V, RL = 100Ω to GROUND VIN = 0.5V _______________________________________________________________________________________ Low-Cost, High-Speed, Single-Supply, Gain of +2 Buffers with Rail-to-Rail Outputs in SOT23 PIN MAX4014 MAX4017 MAX4019 MAX4022 SOT23-5 SO/µMAX SO QSOP SO QSOP — — — 8, 9 — 1 — — — 2 4 11 3 — 4 NAME FUNCTION 8, 9 N.C. No Connect. Not internally connected. Tie to ground or leave open. — — OUT Amplifier Output 13 11 13 VEE Negative Power Supply or Ground (in single-supply operation) — — — — IN+ Noninverting Input — — — — — IN- Inverting Input 5 8 4 4 4 4 VCC Positive Power Supply — 1 7 7 1 1 OUTA — 2 6 6 2 2 INA- Amplifier A Inverting Input — 3 5 5 3 3 INA+ Amplifier A Noninverting Input — 7 8 10 7 7 OUTB Amplifier B Output — 6 9 11 6 6 INB- Amplifier B Inverting Input — 5 10 12 5 5 INB+ Amplifier B Noninverting Input — — 14 16 8 10 OUTC Amplifier C Output — — 13 15 9 11 INC- Amplifier C Inverting Input — — 12 14 10 12 INC+ Amplifier C Noninverting Input — — — — 14 16 OUTD Amplifier D Output — — — — 13 15 IND- Amplifier D Inverting Input — — — — 12 14 IND+ Amplifier D Noninverting Input — — 1 1 — — ENA Enable Input for Amplifier A — — 3 3 — — ENB Enable Input for Amplifier B — — 2 2 — — ENC Enable Input for Amplifier C Amplifier A Output _______________________________________________________________________________________ 7 MAX4014/MAX4017/MAX4019/MAX4022 ______________________________________________________________Pin Description MAX4014/MAX4017/MAX4019/MAX4022 Low-Cost, High-Speed, Single-Supply, Gain of +2 Buffers with Rail-to-Rail Outputs in SOT23 _______________Detailed Description The MAX4014/MAX4017/MAX4019/MAX4022 are single-supply, rail-to-rail output, voltage-feedback, closedloop buffers that employ current-feedback techniques to achieve 600V/µs slew rates and 200MHz bandwidths. These buffers use internal 500Ω resistors to provide a preset closed-loop gain of +2V/V in the noninverting configuration or -1V/V in the inverting configuration. Excellent harmonic distortion and differential gain/phase performance make these buffers an ideal choice for a wide variety of video and RF signal-processing applications. Local feedback around the buffer’ s output stage ensures low output impedance, which reduces gain sensitivity to load variations. This feedback also produces demand-driven current bias to the output transistors for ±120mA drive capability, while constraining total supply current to less than 7mA. __________Applications Information Power Supplies These devices operate from a single +3.15V to +11V power supply or from dual supplies of ±1.575V to ±5.5V. For single-supply operation, bypass the VCC pin to ground with a 0.1µF capacitor as close to the pin as possible. If operating with dual supplies, bypass each supply with a 0.1µF capacitor. Selecting Gain Configuration Each buffer in the MAX4014 family can be configured for a voltage gain of +2V/V or -1V/V. For a gain of +2V/V, ground the inverting terminal. Use the noninverting terminal as the signal input of the buffer (Figure 1a). Grounding the noninverting terminal and using the inverting terminal as the signal input configures the buffer for a gain of -1V/V (Figure 1b). Since the inverting input exhibits a 500Ω input impedance, terminate the input with a 56Ω resistor when the device is configured for an inverting gain in 50Ω applications (terminate with 88Ω in 75Ω applications). Terminate the input with a 49.9Ω resistor in the noninverting case. Output terminating resistors should directly match cable impedances in either configuration. Layout Techniques Maxim recommends using microstrip and stripline techniques to obtain full bandwidth. To ensure that the PC board does not degrade the buffer’s performance, design it for a frequency greater than 1GHz. Pay careful attention to inputs and outputs to avoid large parasitic capacitance. Whether or not you use a constant-impedance board, observe the following guidelines when designing the board: • Don’t use wire-wrapped boards. They are too inductive. • Don’t use IC sockets. They increase parasitic capacitance and inductance. • Use surface-mount instead of through-hole components for better high-frequency performance. • Use a PC board with at least two layers; it should be as free from voids as possible. • Keep signal lines as short and as straight as possible. Do not make 90° turns; round all corners. IN+ IN IN+ OUT RTIN *R OUT OUT RS *R *R *R 500Ω IN 500Ω 500Ω IN- MAX40_ _ Figure 1a. Noninverting Gain Configuration (AV = +2V/V) 8 IN- 500Ω RTIN *RL = 2R OUT MAX40_ _ *RL = 2R Figure 1b. Inverting Gain Configuration (AV = -1V/V) _______________________________________________________________________________________ Low-Cost, High-Speed, Single-Supply, Gain of +2 Buffers with Rail-to-Rail Outputs in SOT23 -1 0 -2 INPUT CURRENT (µA) INPUT CURRENT (µA) -20 -40 -60 -80 -100 -3 -4 -5 -6 -7 -120 -8 -140 -9 -10 -160 0 100 200 300 400 500 Figure 2. Enable Logic-Low Input Current vs. Enable LogicLow Threshold ENABLE 10k IN+ EN_ MAX40_ _ OUT IN500Ω 0 100 200 300 400 500 VIL (mV ABOVE VEE) VIL (mV ABOVE VEE) 500Ω Figure 3. Circuit to Reduce Enable Logic-Low Input Current Input Voltage Range and Output Swing The input range for the MAX4014 family extends from (VEE - 100mV) to (VCC - 2.25V). Input ground sensing increases the dynamic range for single-supply applications. The outputs drive a 2kΩ load to within 60mV of the power-suply rails. With heavier loads, the output swing is reduced as shown in the Electrical Characteristics and the Typical Operating Characteristics. As the load increases, the input range is effectively limited by Figure 4. Enable Logic-Low Input Current vs. Enable LogicLow Threshold with 10kΩ Series Resistor the output-drive capability, since the buffers have a fixed voltage gain of +2 or -1. For example, a 50Ω load can typically be driven from 40mV above VEE to 1.6V below VCC, or 40mV to 3.4V when operating from a single +5V supply. If the buffer is operated in the noninverting, gain of +2 configuration with the inverting input grounded, the effective input voltage range becomes 20mV to 1.7V, instead of the -100mV to 2.75V indicated by the Electrical Characteristics. Beyond the effective input range, the buffer output is a nonlinear function of the input, but it will not undergo phase reversal or latchup. Enable The MAX4019 has an enable feature (EN_) that allows the buffer to be placed in a low-power state. When the buffers are disabled, the supply current will not exceed 550µA per buffer. As the voltage at the EN_ pin approaches the negative supply rail, the EN_ input current rises. Figure 2 shows a graph of EN_ input current versus EN_ pin voltage. Figure 3 shows the addition of an optional resistor in series with the EN pin, to limit the magnitude of the current increase. Figure 4 displays the resulting EN pin input current to voltage relationship. _______________________________________________________________________________________ 9 MAX4014/MAX4017/MAX4019/MAX4022 0 20 MAX4014 MAX4017 MAX4019 MAX4022 IN+ 500Ω 500Ω RISO OUT MAX40_ _ VIN VOUT CL RTIN 50Ω IN500Ω 500Ω Figure 5. Input Protection Circuit Figure 7. Driving a Capacitive Load through an Isolation Resistor conditions, the input protection diodes will be forward biased, lowering the disabled output resistance to 500Ω. 6 Output Capacitive Loading and Stability 5 CL = 15pF 4 3 GIAN (dB) MAX4014/MAX4017/MAX4019/MAX4022 Low-Cost, High-Speed, Single-Supply, Gain of +2 Buffers with Rail-to-Rail Outputs in SOT23 CL = 10pF 2 1 0 CL = 5pF -1 -2 -3 -4 100k 1M 10M 100M 1G FREQUENCY (Hz) Figure 6. Small-Signal Gain vs. Frequency with Load Capacitance and No Isolation Resistor Disabled Output Resistance The MAX4014/MAX4017/MAX4019/MAX4022 include internal protection circuitry that prevents damage to the precision input stage from large differential input voltages, as shown in Figure 5. This protection circuitry consists of five back-to-back Schottky diodes between IN_+ and IN_-. These diodes lower the disabled output resistance from 1kΩ to 500Ω when the output voltage is 3V greater or less than the voltage at IN_+. Under these 10 The MAX4014/MAX4017/MAX4019/MAX4022 provide maximum AC performance with no load capacitance. This is the case when the load is a properly terminated transmission line. However, they are designed to drive up 25pF of load capacitance without oscillating, but with reduced AC performance. Driving large capacitive loads increases the chance of oscillations occurring in most amplifier circuits. This is especially true for circuits with high loop gains, such as voltage followers. The buffer’s output resistance and the load capacitor combine to add a pole and excess phase to the loop response. If the frequency of this pole is low enough to interfere with the loop response and degrade phase margin sufficiently, oscillations can occur. A second problem when driving capacitive loads results from the amplifier’s output impedance, which looks inductive at high frequencies. This inductance forms an L-C resonant circuit with the capacitive load, which causes peaking in the frequency response and degrades the amplifier’s gain margin. Figure 6 shows the frequency response of the MAX4014/ MAX4017/MAX4019/MAX4022 under different capacitive loads. To drive loads with greater than 25pF of capacitance or to settle out some of the peaking, the output requires an isolation resistor like the one shown in ______________________________________________________________________________________ Low-Cost, High-Speed, Single-Supply, Gain of +2 Buffers with Rail-to-Rail Outputs in SOT23 3 RISO = 27Ω CL = 47pF 1 0 20 GIAN (dB) ISOLATION RESISTANCE, RISO (Ω) 2 25 15 10 CL = 68pF -1 -2 CL = 120pF -3 -4 -5 5 -6 0 -7 0 50 100 150 200 CAPACITIVE LOAD (pF) 250 100k 1M 10M 100M 1G FREQUENCY (Hz) Figure 8. Capacitive Load vs. Isolation Resistance Figure 9. Small-Signal Gain vs. Frequency with Load Capacitance and 27Ω Isolation Resistor Figure 7. Figure 8 is a graph of the optimal isolation resistor versus load capacitance. Figure 9 shows the frequency response of the MAX4014/MAX4017/MAX4019/ MAX4022 when driving capacitive loads with a 27Ω isolation resistor. Coaxial cables and other transmission lines are easily driven when properly terminated at both ends with their characteristic impedance. Driving back-terminated transmission lines essentially eliminates the lines’ capacitance. ______________________________________________________________________________________ 11 MAX4014/MAX4017/MAX4019/MAX4022 30 MAX4014/MAX4017/MAX4019/MAX4022 Low-Cost, High-Speed, Single-Supply, Gain of +2 Buffers with Rail-to-Rail Outputs in SOT23 __________________________________________________________Pin Configurations TOP VIEW OUT 1 VEE 2 5 VCC OUTA 1 INA- 2 MAX4014 VCC 7 OUTB 3 6 INB- VEE 4 5 INB+ MAX4017 INA+ IN+ 3 8 4 IN- SO/µMAX SOT23-5 14 OUTC ENA 1 ENC 2 ENB 3 13 INC- MAX4019 12 INC+ VCC 4 11 VEE INA+ 5 10 INB+ INA- 6 9 INB- OUTA 7 8 OUTB SO 16 OUTC ENA 1 ENC 2 15 INC- INA- ENB 3 14 INC+ INA+ MAX4019 14 OUTD OUTA 1 OUTA 1 16 OUTD 2 13 IND- INA- 2 15 IND- 3 12 IND+ INA+ 3 MAX4022 14 IND+ MAX4022 13 VEE VCC 4 11 VEE VCC 4 INA+ 5 12 INB+ INB+ 5 10 INC+ INB+ 5 12 INC+ INA- 6 11 INB- INB- 6 9 INC- INB- 6 11 INC- OUTA 7 10 OUTB OUTB 7 8 OUTC OUTB 7 10 OUTC VCC 4 N.C. 8 9 N.C. N.C. 8 13 VEE 9 N.C. SO QSOP QSOP ___________________Chip Information PART NUMBER NO. OF TRANSISTORS MAX4014 95 MAX4017 190 MAX4019 299 MAX4022 362 SUBSTRATE CONNECTED TO VEE 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 © 1997 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.