MAX4249 MAX4257 UCSP, Single-Supply, Low-Noise, Low-Distortion, Rail-to-Rail Op Amps

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1 EVALUATION KIT AVAILABLE MAX4249 MAX4257 General Description The MAX4249 MAX4257 low-noise, low-distortion operational amplifiers offer rail-to-rail outputs and singlesupply operation down to 2.4V. They draw 4µA of quiescent supply current per amplifier while featuring ultra-low distortion (.2% THD), as well as low input voltage-noise density (7.9nV/!Hz) and low input current-noise density (.5fA/!Hz). These features make the devices an ideal choice for portable/battery-powered applications that require low distortion and/or low noise. For additional power conservation, the MAX4249/ MAX4251/MAX4253/MAX4256 offer a low-power shutdown mode that reduces supply current to.5µa and puts the amplifiers outputs into a high-impedance state. The MAX4249-MAX4257 s outputs swing rail-torail and their input common-mode voltage range includes ground. The MAX425 MAX4254 are unitygain stable with a gain-bandwidth product of 3MHz. The MAX4249/MAX4255/MAX4256/MAX4257 are internally compensated for gains of 1V/V or greater with a gain-bandwidth product of 22MHz. The single MAX425/ MAX4255 are available in space-saving 5-pin SOT23 packages. The MAX4252 is available in an 8-bump chipscale package (UCSP ) and the MAX4253 is available in a 1-bump UCSP. The MAX425AAUK comes in a 5-pin SOT23 package and is specified for operation over the automotive (-4 C to +125 C) temperature range. Applications Wireless Communications Devices PA Control Portable/Battery-Powered Equipment Medical Instrumentation ADC Buffers Digital Scales/Strain Gauges Features Available in Space-Saving UCSP, SOT23, and µmax Packages Low Distortion:.2% THD (1k" load) 4µA Quiescent Supply Current per Amplifier Single-Supply Operation from 2.4V to 5.5V Input Common-Mode Voltage Range Includes Ground Outputs Swing Within 8mV of Rails with a 1k" Load 3MHz GBW Product, Unity-Gain Stable (MAX425 MAX4254) 22MHz GBW Product, Stable with A V # 1V/V (MAX4249/MAX4255/MAX4256/MAX4257) Excellent DC Characteristics V OS = 7µV I BIAS = 1pA Large-Signal Voltage Gain = 116dB Low-Power Shutdown Mode Reduces Supply Current to.5µa Places Outputs in a High-Impedance State 4pF Capacitive-Load Handling Capability PART Ordering Information TEMP RANGE PIN- PACKAGE Ordering Information continued at end of data sheet. Selector Guide appears at end of data sheet. TOP MARK MAX4249ESD+ -4 C to +85 C 14 SO MAX4249EUB+ -4 C to +85 C 1 µmax MAX425EUK+T -4 C to +85 C 5 SOT23 ACCI M AX 425AAU K+ T - 4 C to C 5 SOT23 AEYJ +Denotes a lead(pb)-free/rohs-compliant package. T = Tape and reel. Pin/Bump Configurations TOP VIEW (BUMPS ON BOTTOM) A1 A2 A3 A4 A OUTA V DD OUTB OUTB INB- INB+ SHDNB B1 B4 B INA- MAX4252 INB- V DD MAX4253 C INA+ INB+ C1 OUTA C2 C3 C4 INA- INA+ SHDNA UCSP Pin/Bump Configurations continued at end of data sheet. UCSP UCSP is a trademark and µmax is a registered trademark of Maxim Integrated Products, Inc. For pricing, delivery, and ordering information, please contact Maxim Direct at , or visit Maxim Integrated s website at ; Rev 9; 12/12

2 ABSOLUTE MAXIMUM RATINGS Power-Supply Voltage (V DD to )...+6.V to -.3V Analog Input Voltage (IN_+, IN_-)...(V DD +.3V) to ( -.3V) SHDN Input Voltage...6.V to ( -.3V) Output Short-Circuit Duration to Either Supply...Continuous Continuous Power Dissipation (T A = +7 C) 5-Pin SOT23 (derate 7.1mW/ C above +7 C)...571mW 8-Bump UCSP (derate 4.7mW/ C above +7 C)...379mW 8-Pin µmax (derate 4.5mW/ C above +7 C)...362mW 8-Pin SO (derate 5.88mW/ C above +7 C)...471mW 1-Bump UCSP (derate 6.1mW/ C above +7 C)...484mW 1-Pin µmax (derate 5.6mW/ C above +7 C)...444mW 14-Pin SO (derate 8.33mW/ C above +7 C)...667mW Operating Temperature Range...-4 C to +85 C MAX425AAUK...-4 C to +125 C Junction Temperature C Storage Temperature Range C to +15 C Lead Temperature (soldering, 1s)...+3 C Soldering Temperature (reflow) 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 (V DD = 5V, = V, V CM = V, = V DD /2, R L connected to V DD /2, SHDN = V DD, T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +25 C.) (Notes 2, 3) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Supply Voltage Range V DD (Note 4) V 4 Quiescent Supply Current Per Amplifier I Q Normal mode V DD = 5V E temperature MAX425AAUK 675 V DD = 5V, UCSP only µa Shutdown mode (SHDN = ) (Note 2) E temperature ±.7 ±.75 Input Offset Voltage (Note 5) V OS MAX425AAUK ±1.85 mv Input Offset Voltage Tempco TCV OS.3 µv/ C Input Bias Current I B (Note 6) Input Offset Current I OS (Note 6) T A = +25 C.1 1 T A = -4 C to +85 C 5 T A = -4 C to +125 C 15 T A = +25 C.1 1 T A = -4 C to +85 C 1 T A = -4 C to +125 C 1 Differential Input Resistance R IN 1 GΩ Input Common-Mode Voltage Range Common-Mode Rejection Ratio V CM CMRR Guaranteed by E temperature -.2 V DD -1.1 CMRR test MAX425AAUK V DD V V CM E temperature V DD - 1.1V MAX425AAUK 68 pa pa V db 2 Maxim Integrated

3 ELECTRICAL CHARACTERISTICS (continued) (V DD = 5V, = V, V CM = V, = V DD /2, R L connected to V DD /2, SHDN = V DD, T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +25 C.) (Notes 2, 3) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Power-Supply Rejection Ratio PSRR V DD 2.4V to 5.5V E temperature 75 1 MAX425AAUK 72 R L = 1kΩ to V DD /2; = 25mV to V DD 4.97V E temperature MAX425AAUK Large-Signal Voltage Gain A V R L = 1kΩ to V DD /2; = 15V to V DD 4.75V E temperature MAX425AAUK Output Voltage Swing mV; R L = 1kΩ to V DD /2 V DD - V OH E 8 25 A 3 V OL - E 7 2 A 25 db db mv Output Voltage Swing mV, R L = 1kΩ to V DD /2 E 77 2 V DD - V OH A 225 E 47 1 V OL - A 125 mv Output Short-Circuit Current I SC 68 ma Output Leakage Current I LEAK Shutdown mode (SHDN = ), = to V DD (Note 2).1 1. µa SHDN Logic Low V IL (Note 2).2 X V D D V SHDN Logic High V IH (Note 2).8 X V DD V SHDN Input Current I IL /I IH SHDN = = V DD (Note 2) µa Input Capacitance 11 pf Gain-Bandwidth Product Slew Rate Peak-to-Peak Input-Noise Voltage GBW SR MAX425 MAX MAX4249/MAX4255/MAX4256/MAX MAX425 MAX MAX4249/MAX4255/MAX4256/MAX e n P-P f =.1Hz to 1Hz 76 nv P-P f = 1Hz 27 Input Voltage-Noise Density e n f = 1kHz 8.9 f = 3kHz 7.9 MHz V/µs nv/ Hz Input Current-Noise Density i n f = 1kHz.5 fa/ Hz Maxim Integrated 3

4 ELECTRICAL CHARACTERISTICS (continued) (V DD = 5V, = V, V CM = V, = V DD /2, R L connected to V DD /2, SHDN = V DD, T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +25 C.) (Notes 2, 3) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Total Harmonic Distortion Plus Noise THD+N MAX425 MAX4254 A V = 1V/V, = 2V P-P, f = 1kHz.4 R L = 1kΩ to GND (Note 7) f = 2kHz.6 MAX4249/MAX4255/ MAX4256/MAX4257 f = 1kHz.12 A V = 1V/V, = 2V P-P, R L = 1kΩ to GND (Note 7) f = 2kHz.7 % Capacitive-Load Stability No sustained oscillations 4 pf MAX425 MAX4254, A V = 1V/V 1 Gain Margin GM MAX4249/MAX4255/MAX4256/MAX4257, A V = 1V/V 12.5 db MAX425 MAX4254, A V = 1V/V 74 Phase Margin ΦM MAX4249/MAX4255/MAX4256/MAX4257, A V = 1V/V 68 Degrees Settling Time To.1%, = 2V step MAX425 MAX MAX4249/MAX4255/ MAX4256/MAX µs Delay Time to Shutdown t SH normal I VDD = 5% of MAX4251/MAX operation MAX4249/MAX µs Delay Time to Enable t EN settles to = 2.5V, MAX4251/MAX % MAX4249/MAX Power-Up Delay Time t PU V DD = to 5V step, stable to.1% 6 µs Note 2: SHDN is available on the MAX4249/MAX4251/MAX4253/MAX4256 only. Note 3: All device specifications are 1% tested at T A = +25 C. Limits over temperature are guaranteed by design. Note 4: Guaranteed by the PSRR test. Note 5: Offset voltage prior to reflow on the UCSP. Note 6: Guaranteed by design. Note 7: Lowpass-filter bandwidth is 22kHz for f = 1kHz and 8kHz for f = 2kHz. Noise floor of test equipment = 1nV/!Hz. µs 4 Maxim Integrated

5 NUMBER OF UNITS OUTPUT VOLTAGE (V) MAX4251/MAX4256 INPUT OFFSET VOLTAGE DISTRIBUTION V OS (µv) 4 UNITS V CM = T A = +25 C OUTPUT VOLTAGE vs. OUTPUT LOAD CURRENT OR 5V V DIFF = ±1mV V DD - V OH V OL OUTPUT LOAD CURRENT (ma) MAX TOC1 MAX TOC4 VOS (µv) VDD - VOH (V) V CM = OFFSET VOLTAGE vs. TEMPERATURE TEMPERATURE ( C) OUTPUT VOLTAGE SWING (V OH ) vs. TEMPERATURE.2 R L = 1kΩ.1 R L = 1kΩ TEMPERATURE ( C) R L = 1kΩ MAX4249 MAX4257 Typical Operating Characteristics (V DD = 5V, = V, V CM = = V DD /2, input noise floor of test equipment =1nV/!Hz for all distortion measurements, T A = +25 C, unless otherwise noted.) MAX TOC2 MAX TOC5 INPUT OFFSET VOLTAGE (µv) VOL (V) INPUT OFFSET VOLTAGE vs. INPUT COMMON-MODE VOLTAGE V DD = 5V INPUT COMMON-MODE VOLTAGE (V) OUTPUT VOLTAGE SWING (V OL ) vs. TEMPERATURE TEMPERATURE ( C) R L = 1kΩ R L = 1kΩ R L = 1kΩ MAX TOC3 MAX TOC6 AV (db) LARGE-SIGNAL VOLTAGE GAIN vs. OUTPUT VOLTAGE SWING R L = 2kΩ R L = 2kΩ R L = 2kΩ R L REFERENCED TO GND SWING FROM EITHER SUPPLY (mv) MAX TOC7 AV (db) LARGE-SIGNAL VOLTAGE GAIN vs. OUTPUT VOLTAGE SWING R L = 2kΩ R L = 2kΩ R L = 2kΩ 7 R L REFERENCED TO GND SWING FROM EITHER SUPPLY (mv) MAX TOC8 AV (db) LARGE-SIGNAL VOLTAGE GAIN vs. OUTPUT VOLTAGE SWING R L = 2kΩ R L = 2kΩ R L = 2kΩ V DD = 5V R L REFERENCED TO GND SWING FROM EITHER SUPPLY (mv) MAX TOC9 Maxim Integrated 5

6 AV (db) MAX4249 MAX LARGE-SIGNAL VOLTAGE GAIN vs. OUTPUT VOLTAGE SWING R L = 2kΩ R L = 2kΩ R L = 2kΩ V DD = 5V R L REFERENCED TO GND SWING FROM EITHER SUPPLY (mv) MAX TOC1 AV (db) Typical Operating Characteristics (continued) (V DD = 5V, = V, V CM = = V DD /2, input noise floor of test equipment =1nV/!Hz for all distortion measurements, T A = +25 C, unless otherwise noted.) LARGE-SIGNAL VOLTAGE GAIN vs. TEMPERATURE R L REFERENCED TO V DD /2 V DD = 5V R L = 1kΩ = 15mV TO 4.75mV R L = 1kΩ = 1mV TO 4.99mV R L = 1kΩ = 2mV TO 4.975mV TEMPERATURE ( C) MAX TOC11 SUPPLY CURRENT (µa) SUPPLY CURRENT AND SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE MAX TOC12 PER AMPLIFIER SHDN = V DD SHDN = TEMPERATURE ( C) SHUTDOWN SUPPLY CURRENT (µa) SUPPLY CURRENT (µa) SUPPLY CURRENT AND SHUTDOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX TOC13.6 PER AMPLIFIER SHDN = V DD SHDN = SHUTDOWN SUPPLY CURRENT (µa) SUPPLY CURRENT (µa) SUPPLY CURRENT vs. OUTPUT VOLTAGE V DD = 5V MAX TOC14 VOS (µv) INPUT OFFSET VOLTAGE vs. SUPPLY VOLTAGE V CM = = V DD /2 R L REFERENCED TO GND R L = 1kΩ R L = 1kΩ R L = 1kΩ MAX TOC SUPPLY VOLTAGE (V) OUTPUT VOLTAGE (V) SUPPLY VOLTAGE (V) GAIN (db) MAX425 MAX4254 GAIN AND PHASE vs. FREQUENCY PHASE GAIN k 1k 1k 1M MAX TOC16, 5V R L = 5kΩ C L = 2pF A V = M PHASE (DEGREES) GAIN (db) MAX4249/MAX4255/MAX4256/MAX4257 GAIN AND PHASE vs. FREQUENCY MAX TOC , 5V 5 R L = 5kΩ C L = 2pF A V = 1 GAIN PHASE k 1k 1k 1M M PHASE (DEGREES) PSRR (db) MAX425 MAX4254 POWER-SUPPLY REJECTION RATIO vs. FREQUENCY, 5V PSRR+ PSRR k 1k 1k 1M 1M MAX TOC18 6 Maxim Integrated

7 OUTPUT IMPEDANCE (Ω) AMPLITUDE (dbc) OUTPUT IMPEDANCE vs. FREQUENCY A V = 1 (MAX4249/MAX4255/ MAX4256/MAX4257) A V = 1 (MAX425 MAX4254).1 1k 1k 1k 1M 1M MAX425 MAX4254 FFT OF DISTORTION AND NOISE = 2V P-P f O R L = 1kΩ f O = 1kHz A V = 1 MAX TOC19 MAX TOC22 AMPLITUDE (dbc) Vn-EQUIVALENT INPUT NOISE-VOLTAGE (nv/ Hz) INPUT VOLTAGE-NISE DENSITY vs. FREQUENCY 1 1 1k 1k 1k MAX4249/MAX4255/MAX4256/MAX4257 FFT OF DISTORTION AND NOISE f O 11kΩ 1kΩ = 4V P-P f O = 1kHz V O MAX4249 MAX4257 Typical Operating Characteristics (continued) (V DD = 5V, = V, V CM = = V DD /2, input noise floor of test equipment =1nV/!Hz for all distortion measurements, T A = +25 C, unless otherwise noted.) 1kΩ MAX TOC2 MAX TOC23 2nV/div THD+N (%) OR 5V.1Hz TO 1Hz P-P NOISE V P-PNOISE = 76nV P-P 1s/div MAX425 MAX4254 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT VOLTAGE (V DD = 5V) A V = 1 f O = 3kHz FILTER BW = 3kHz R L = 1kΩ 11kΩ 1kΩ V O R L MAX TOC21 MAX TOC24 THD+N (%) HD2 HD4 HD5 HD k 1k 15k 2k MAX425 MAX4254 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT VOLTAGE SWING () 1 R L = 1kΩ 11kΩ A V = 1 f O = 3kHz FILTER BW = 3kHz 1kΩ OUTPUT VOLTAGE (V P-P ) R L = 1kΩ R L R L = 1kΩ MAX TOC25 THD+N (%) HD2 HD k 1k 15k 2k MAX4249/MAX4255/MAX4256/MAX4257 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT VOLTAGE SWING 1 A V = 1 11kΩ 1kΩ f O = 2kHz, FILTER BW = 8kHz f O = 3kHz, FILTER BW = 3kHz OUTPUT VOLTAGE (V P-P ) R L MAX TOC26 THD+N (%) R L = 1kΩ OUTPUT VOLTAGE (V P-P ) R L = 1kΩ MAX425 MAX4254 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY R1 R1 = 56Ω, R2 = 53kΩ R2 R1 = 5.6kΩ, R2 = 53kΩ A V = k 1k R L A V = 1 A V = 1 FILTER BW = 22kHz R L = 1kΩ TO GND V O = 2V P-P MAX TOC27 Maxim Integrated 7

8 Typical Operating Characteristics (continued) (V DD = 5V, = V, V CM = = V DD /2, input noise floor of test equipment =1nV/!Hz for all distortion measurements, T A = +25 C, unless otherwise noted.) THD+N(%).1.1 MAX425 MAX4254 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY FILTER BW = 8kHz A V = 1 R L = 1kΩ = 2V P-P R L TO V DD /2 R L TO GND MAX TOC28 1.5V 2mV/div MAX425 MAX4254 LARGE-SIGNAL PULSE RESPONSE MAX TOC29.6V 2mV/div MAX425 MAX4254 SMALL-SIGNAL PULSE RESPONSE MAX TOC k 1k R L TO V DD.5V R L = 1kΩ C L = 1pF = 1V PULSE 2µs/div.5V R L = 1kΩ C L = 1pF = 1V PULSE 2µs/div 2V 2mV/div 1V MAX4249/MAX4255/MAX4256/MAX4257 LARGE-SIGNAL PULSE RESPONSE R L = 1kΩ C L = 1pF = 1mV PULSE A V = 1 2µs/div MAX TOC31 1.6V 5mV/div 1.5V MAX4249/MAX4255/MAX4256/MAX4257 SMALL-SIGNAL PULSE RESPONSE R L = 1kΩ C L = 1pF = 1mV PULSE A V = 1 2µs/div MAX TOC32 CHANNEL SEPARATION (db) CHANNEL SEPARATION vs. FREQUENCY 1k 1k 1k 1M MAX TOC33 1M 8 Maxim Integrated

9 Pin/Bump Description PIN/BUMP M A X4 2 5 / M A X PIN SOT23 M A X / M A X PIN SO/µMAX M A X / M A X PIN SO/µMAX M A X BUMP UCSP 1-BUMP UCSP M A X / M A X PIN µmax PIN SO M A X PIN SO NAME FUNCTION 1 6 1, 7 A1, A3 A1, C1 1, 9 1, 13 1, 7, 8, 14 OUT, OUTA, OUTB, OUTC, OUTD Amplifier Output C2 B Connect to ground for singlesupply Negative Supply. operation 3 3 3, 5 C1, C3 A3, C3 3, 7 3, , 6 B1, B3 A2, C2 2, 8 2, 12 3, 5, 1, 12 2, 6, 9, 13 IN +, IN A+, IN B+, IN C +, IN D + IN-, INA-, INB-, INC-, IND- Noninverting Amplifier Input Inverting Amplifier Input A2 B V DD Positive Supply 8 A4, C4 5, 6 6, 9 SHDN, SHDNA, SHDNB Shutdown Input, Connect to V DD or leave unconnected for normal operation (amplifier(s) enabled). 1, 5 5, 7, 8, 1 N.C. B2 B2, B3 No Connection. Not internally connected. Not populated with solder sphere Detailed Description The MAX4249 MAX4257 single-supply operational amplifiers feature ultra-low noise and distortion while consuming very little power. Their low distortion and low noise make them ideal for use as preamplifiers in wide dynamic-range applications, such as 16-bit analog-todigital converters (see Typical Operating Circuit). Their high-input impedance and low noise are also useful for signal conditioning of high-impedance sources, such as piezoelectric transducers. These devices have true rail-to-rail output operation, drive loads as low as 1k" while maintaining DC accuracy, and can drive capacitive loads up to 4pF without oscillation. The input common-mode voltage range extends from V DD - 1.1V to 2mV beyond the negative rail. The push-pull output stage maintains excellent DC characteristics, while delivering up to ±5mA of current. The MAX are unity-gain stable, whereas, the MAX4249/MAX4255/MAX4256/MAX4257 have a higher slew rate and are stable for gains # 1V/V. The MAX4249/MAX4251/MAX4253/MAX4256 feature a lowpower shutdown mode, which reduces the supply current to.5µa and disables the outputs. The MAX425AAUK is specified for operation over the automotive (-4 C to +125 C) temperature range. Maxim Integrated 9

10 Low Distortion Many factors can affect the noise and distortion that the device contributes to the input signal. The following guidelines offer valuable information on the impact of design choices on Total Harmonic Distortion (THD). Choosing proper feedback and gain resistor values for a particular application can be a very important factor in reducing THD. In general, the smaller the closedloop gain, the smaller the THD generated, especially when driving heavy resistive loads. Large-value feedback resistors can significantly improve distortion. The THD of the part normally increases at approximately 2dB per decade, as a function of frequency. Operating the device near or above the full-power bandwidth significantly degrades distortion. Referencing the load to either supply also improves the part s distortion performance, because only one of the MOSFETs of the push-pull output stage drives the output. Referencing the load to midsupply increases the part s distortion for a given load and feedback setting. (See the Total Harmonic Distortion vs. Frequency graph in the Typical Operating Characteristics.) For gains # 1V/V, the decompensated devices MAX4249/MAX4255/MAX4256/MAX4257 deliver the best distortion performance, since they have a higher slew rate and provide a higher amount of loop gain for a given closed-loop gain setting. Capacitive loads below 4pF, do not significantly affect distortion results. Distortion performance remains relatively constant over supply voltages. R G Figure 1. Adding Feed-Forward Compensation 1mV A V = 2V/V R F = R G = 1kΩ R F C Z = 5mV/div = 1mV/div Low Noise The amplifier s input-referred, noise-voltage density is dominated by flicker noise at lower frequencies, and by thermal noise at higher frequencies. Because the thermal noise contribution is affected by the parallel combination of the feedback resistive network (R F R G, Figure 1), these resistors should be reduced in cases where the system bandwidth is large and thermal noise is dominant. This noise contribution factor decreases, however, with increasing gain settings. For example, the input noise-voltage density of the circuit with R F = 1k", R G = 11k" (A V = 1V/V) is en = 15nV/!Hz, en can be reduced to 9nV/!Hz by choosing R F = 1k", R G = 1.1k" (A V = 1V/V), at the expense of greater current consumption and potentially higher distortion. For a gain of 1V/V with R F = 1k", R G = 1.1k", the en is low (9nV/!Hz). 1mV A V = 2 R F = R G = 1kΩ C Z = 11pF 2µs/div Figure 2a. Pulse Response with No Feed-Forward Compensation 2µs/div 5mV/div 1mV/div Figure 2b. Pulse Response with 1pF Feed-Forward Compensation 1 Maxim Integrated

11 MAX425 MAX4251 MAX4252 MAX4253 MAX4254 R ISO Figure 3. Overdriven Input Showing No Phase Reversal 4.25V 4.45V 2µs/div Figure 4. Rail-to-Rail Output Operation 5V V DD = 5V R L = 1kΩ A V = 1 f = 1kHz 2µs/div Figure 5. Capacitive-Load Driving Circuit A V = 1 V DD = 5V R L = 1kΩ C L -2mV 1V/div Using a Feed-Forward Compensation Capacitor, C Z The amplifier s input capacitance is 11pF. If the resistance seen by the inverting input is large (feedback network), this can introduce a pole within the amplifier s bandwidth, resulting in reduced phase margin. Compensate the reduced phase margin by introducing a feed-forward capacitor (C Z ) between the inverting input and the output (Figure 1). This effectively cancels the pole from the inverting input of the amplifier. Choose the value of C Z as follows: C Z = 11 x (R F / R G ) [pf] In the unity-gain stable MAX425 MAX4254, the use of a proper C Z is most important for A V = 2V/V, and A V = -1V/V. In the decompensated MAX4249/ MAX4255/MAX4256/MAX4257, C Z is most important for A V = 1V/V. Figures 2a and 2b show transient response both with and without C Z. Using a slightly smaller C Z than suggested by the formula above achieves a higher bandwidth at the expense of reduced phase and gain margin. As a general guideline, consider using C Z for cases where R G R F is greater than 2k" (MAX425 MAX4254) or greater than 5k" (MAX4249/MAX4255/MAX4256/ MAX4257). Applications Information The MAX4249 MAX4257 combine good driving capability with ground-sensing input and rail-to-rail output operation. With their low distortion, low noise, and lowpower consumption, these devices are ideal for use in portable instrumentation systems and other low-power, noise-sensitive applications. Ground-Sensing and Rail-to-Rail Outputs The common-mode input range of these devices extends below ground, and offers excellent commonmode rejection. These devices are guaranteed not to undergo phase reversal when the input is overdriven (Figure 3). Figure 4 showcases the true rail-to-rail output operation of the amplifier, configured with A V = 1V/V. The output swings to within 8mV of the supplies with a 1k" load, making the devices ideal in low-supplyvoltage applications. Output Loading and Stability Even with their low quiescent current of 4µA, these amplifiers can drive 1k" loads while maintaining excellent DC accuracy. Stability while driving heavy capacitive loads is another key feature. Maxim Integrated 11

12 RISO (Ω) SHADED AREA INDICATES STABLE OPERATION WITH NO NEED FOR ISOLATION RESISTOR , CAPACITIVE LOADING (pf) UNITY-GAIN BANDWIDTH (MHz) SHADED AREA INDICATES STABLE OPERATION WITH NO NEED FOR ISOLATION RESISTOR , CAPACITIVE LOAD (pf) NOTE: USING AN ISOLATION RESISTOR REDUCES PEAKING. NOTE: R ISO CHOSEN FOR PEAKING <2dB. Figure 6. Isolation Resistance vs. Capacitive Loading to Minimize Peaking (<2dB) Figure 8. MAX425 MAX4254 Unity-Gain Bandwidth vs. Capacitive Load PEAKING (db) MAX425 MAX4254 (A V = 1) MAX4249/MAX4255 MAX4257 (A V = 1) R ISO = SHADED AREA INDICATES STABLE OPERATION WITH NO NEED FOR ISOLATION RESISTOR , CAPACITIVE LOAD (pf) Figure 7. Peaking vs. Capacitive Load These devices maintain stability while driving loads up to 4pF. To drive higher capacitive loads, place a small isolation resistor in series between the output of the amplifier and the capacitive load (Figure 5). This resistor improves the amplifier s phase margin by isolating the capacitor from the op amp s output. Reference Figure 6 to select a resistance value that will ensure a load capacitance that limits peaking to <2dB (25%). For example, if the capacitive load is 1pF, the corresponding isolation resistor is 15". Figure 7 shows that peaking occurs without the isolation resistor. Figure 8 shows the unity-gain bandwidth vs. capacitive load for the MAX425 MAX4254. Power Supplies and Layout The MAX4249 MAX4257 operate from a single 2.4V to 5.5V power supply or from dual supplies of ±1.2V to ±2.75V. For single-supply operation, bypass the power supply with a.1µf ceramic capacitor placed close to the V DD pin. If operating from dual supplies, bypass each supply to ground. Good layout improves performance by decreasing the amount of stray capacitance and noise at the op amp s inputs and output. To decrease stray capacitance, minimize PC board trace lengths and resistor leads, and place external components close to the op amp s pins. 12 Maxim Integrated

13 Typical Operating Circuit 5V 5kΩ V DD 5kΩ MAX AIN SHDN MAX195 (16-BIT ADC) DOUT SCLK CS REF 4.96V SERIAL INTERFACE -5V SHDN PART G A IN B A N D WID T H ( M H z) MINIMUM STABLE GAIN (V/V) NO. OF AMPLIFIERS PER PACKAGE SHUTDOWN MODE Selector Guide PIN-PACKAGE MAX Yes 1-pin µmax, 14-pin SO MAX425/A pin SOT23 MAX Yes 8-pin µmax/so MAX p i n µm AX /S O, 8- b um p U C S P MAX Yes MAX pin SO 1-pin µmax, 14-pin SO, 1-bump UCSP MAX pin SOT23 MAX Yes 8-pin µmax/so MAX pin µmax/so Maxim Integrated 13

14 Pin/Bump Configurations (continued) TOP VIEW OUT V DD N.C. 1 8 SHDN OUTA 1 8 V DD 2 MAX425 MAX425A MAX4255 IN+ 2 3 MAX4251 MAX V DD OUT INB- INA- INA+ 2 3 MAX4252 MAX OUTB IN- IN+ 3 4 IN- 4 5 N.C. 4 5 INB+ SOT23 µmax/so µmax/so OUTA V DD OUTA V DD OUTA OUTD MAX4249 MAX MAX4249 MAX IND- IND+ INC+ INA- INA+ V DD INB MAX OUTB INB- INB+ SHDNB INA- INA+ SHDNA OUTB INB- INB+ N.C. INA- INA+ N.C. µmax SHDNA N.C SHDNB N.C. INC- OUTC INB- OUTB SO SO Ordering Information (continued) PART TEMP RANGE PIN- PACKAGE TOP M ARK MAX4251ESA+ -4 C to +85 C 8 SO MAX4251EUA+ -4 C to +85 C 8 µmax MAX4252EBL+T -4 C to +85 C 8 UCSP AAO MAX4252ESA+ -4 C to +85 C 8 SO MAX4252EUA+ -4 C to +85 C 8 µmax MAX4253EBC+T -4 C to +85 C 1 UCSP AAK MAX4253EUB+ -4 C to +85 C 1 µmax MAX4253ESD+ -4 C to +85 C 14 SO MAX4254ESD+ -4 C to +85 C 14 SO MAX4255EUK+T -4 C to +85 C 5 SOT23 AC C J MAX4256ESA+ -4 C to +85 C 8 SO MAX4256EUA+ -4 C to +85 C 8 µmax MAX4257ESA+ -4 C to +85 C 8 SO MAX4257ESA/V+ T -4 C to +85 C 8 SO MAX4257EUA+ -4 C to +85 C 8 µmax 14 Maxim Integrated

15 Package Information For the latest package outline information and land patterns (footprints), go to Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO. 5 SOT-23 U µmax U µmax U x 3 µcsp B SOIC S µcsp B Maxim Integrated 15

16 Revision History REVISION NUMBER REVISION DATE 8 1/11 DESCRIPTION Added lead-free packaging to the Ordering Information and changed the Input Bias Current and Input Offset Current conditions in the Electrical Characteristics table PAGES CHANGED 9 12/12 Added MAX4257ESA/V+T to Ordering Information. 14 1, 2, 14 Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. 16 Maxim Integrated 16 Rio Robles, San Jose, CA USA Maxim Integrated Products, Inc. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.