36V, Precision, Low-Power, 90µA, Dual Op Amp

Transcription

1 EVALUATION KIT AVAILABLE MAX V, Precision, Low-Power, 9µA, Dual Op Amp General Description The MAX44248 is an ultra-precision, low-noise, zero-drift dual operational amplifier featuring very low-power operation with a wide supply range. The device incorporates a patented auto-zero circuit that constantly measures and compensates the input offset to eliminate drift over time and temperature as well as the effect of /f noise. The device also features integrated EMI filters to reduce high-frequency signal demodulation on the output. The op amp operates from either a single 2.7V to 36V supply or dual ±.3V to ±8V supply. The device is unity-gain stable with a MHz gain-bandwidth product and a low 9µA supply current per amplifier. The low offset and noise specifications and high supply range make the device ideal for sensor interfaces and transmitters. The device is available in 8-pin FMAXM and SO packages and is specified over the -4NC to +2NC automotive operating temperature range. Sensors Interfaces 4-2mA and tov Transmitters PLC Analog I/O Modules Weight Scales Portable Medical Devices Applications S Very Low Input Voltage Offset 7.µV (max) S Low 3nV/NC Offset Drift (max) S Low 9µA Quiescent Current per Amplifier S Low Input Noise nv/ Hz at khz.µv P-P from.hz to Hz S MHz Gain-Bandwidth Product S EMI Suppression Circuitry S Rail-to-Rail Output S 2.7V to 36V Supply Range S 8-Pin µmax and SO package Ordering Information appears at end of data sheet. Features For related parts and recommended products to use with this part, refer to µmax is a registered trademark of Products, Inc. Typical Operating Circuit LP+ MAX633 REF MAX26 DAC R2 V REF R MAX44248 I SIG (4-2mA) R3 R SENSE LP- For pricing, delivery, and ordering information, please contact Maxim Direct at , or visit Maxim s website at ; Rev ; 7/2

2 36V, Precision, Low-Power, 9µA, Dual Op Amp ABSOLUTE MAXIMUM RATINGS V DD to V SS...-.3V to +4V Common-Mode Input Voltage...(V SS -.3V) to (V DD +.3V) Differential Input Voltage IN_+, IN_-...6V Continuous Input Current Into Any Pin... Q2mA Output Voltage to V SS (OUT_)....3V to (V DD +.3V) Output Short-Circuit Duration (OUT_)... s Operating Temperature Range... -4NC to +2NC Storage Temperature... -6NC to +NC Junction Temperature...+NC Lead Temperature (soldering, s)...+3nc Soldering Temperature (reflow)...+26nc PACKAGE THERMAL CHARACTERISTICS (Note ) FMAX Junction-to-Ambient Thermal Resistance (B JA ) NC/W Junction-to-Case Thermal Resistance (B JC )...42NC/W SO Junction-to-Ambient Thermal Resistance (B JA )...32NC/W Junction-to-Case Thermal Resistance (B JC )...38NC/W Note : Package thermal resistances were obtained using the method described in JEDEC specification JESD-7, using a four-layer board. For detailed information on package thermal considerations, refer to 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 = V, V SS = V, V IN+ = V IN- = V DD /2, R L = ki to V DD /2, T A = -4NC to +2NC, unless otherwise noted. Typical values are at +2NC.) (Note 2) POWER SUPPLY PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Supply Voltage Range V DD Guaranteed by PSRR V Power-Supply Rejection Ratio (Note 3) PSRR T A = +2NC, V IN+ = V IN- = V DD /2 - V NC < T A < +2NC 33 T A = +2NC 9 2 Quiescent Current per Amplifier I DD -4NC < T A < +2NC 3 DC SPECIFICATIONS Input Common-Mode Range V CM Guaranteed by CMRR test Common-Mode Rejection Ratio (Note 3) CMRR T A = +2NC, V CM = V SS -.V to V DD -.V -4NC < T A < +2NC, V CM = V SS -.V to V DD -.V V SS T A = +2NC 2 7. Input Offset Voltage (Note 3) V OS -4NC < T A < +2NC Input Offset Voltage Drift (Note 3) V DD -. TC V OS 3 nv/nc T A = +2NC 3 Input Bias Current (Note 3) I B -4NC < T A < +2NC 7 T A = +2NC 3 6 Input Offset Current (Note 3) I OS -4NC < T A < +2NC 4 2 FA V FV pa pa 2

3 36V, Precision, Low-Power, 9µA, Dual Op Amp ELECTRICAL CHARACTERISTICS (continued) (V DD = V, V SS = V, V IN+ = V IN- = V DD /2, R L = ki to V DD /2, T A = -4NC to +2NC, unless otherwise noted. Typical values are at +2NC.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Open-Loop Gain (Note 3) AVOL V SS +.V P V OUT P V DD -.V T A = +2NC 4-4NC < T A < +2NC 3 Output Short-Circuit Current To V DD or V SS, noncontinuous 4 ma Output Voltage Swing AC SPECIFICATIONS V DD T A = +2NC 8 V OUT -4NC < T A < +2NC V OUT T A = +2NC V SS -4NC < T A < +2NC 7 Input Voltage-Noise Density e N f = khz nv/ Hz Input Voltage Noise.Hz < f < Hz nv P-P Input Current-Noise Density i N f = khz. pa/ Hz Gain-Bandwidth Product GBW MHz Slew Rate SR A V = V/V, V OUT = 2V P-P.7 V/Fs Capacitive Loading C L No sustained oscillation, A V = V/V 4 pf Total Harmonic Distortion Plus Noise EMI Rejection Ratio EMIRR V RF_PEAK = mv THD+N V OUT = 2V P-P, A V = +V/V, f = khz - f = 4MHz 7 f = 9MHz 78 f = 8MHz 8 f = 24MHz 9 mv ELECTRICAL CHARACTERISTICS (V DD = 3V, V SS = V, V IN+ = V IN- = V DD /2, R L = ki to V DD /2, T A = -4NC to +2NC, unless otherwise noted. Typical values are at +2NC.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS POWER SUPPLY T A = +2NC 9 2 Quiescent Current per Amplifier I DD -4NC < T A < +2NC 3 DC SPECIFICATIONS Input Common-Mode Range V CM Guaranteed by CMRR test Common-Mode Rejection Ratio (Note 3) CMRR T A = +2NC, V CM = V SS -.V to V DD -.V -4NC < T A < +2NC, V CM = V SS -.V to V DD -.V V SS V DD -. FA V 3

4 36V, Precision, Low-Power, 9µA, Dual Op Amp ELECTRICAL CHARACTERISTICS (continued) (V DD = 3V, V SS = V, V IN+ = V IN- = V DD /2, R L = ki to V DD /2, T A = -4NC to +2NC, unless otherwise noted. Typical values are at +2NC.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS T A = +2NC 2 7. Input Offset Voltage (Note 3) V OS -4NC < T A < +2NC Input Offset Voltage Drift (Note 3) TC V OS 3 nv/ C T A = +2NC 3 Input Bias Current (Note 3) I B -4NC < T A < +2NC 7 T A = +2NC 3 6 Input Offset Current (Note 3) I OS -4NC < T A < +2NC 4 Open-Loop Gain (Note 3) A VOL V SS +.V P V OUT P V DD -.V T A = +2NC 46-4NC < T A < +2NC 4 Output Short-Circuit Current To V DD or V SS, noncontinuous 4 ma Output Voltage Swing AC SPECIFICATIONS V DD T A = +2NC 2 -V OUT -4NC < T A < +2NC 27 V OUT - T A = +2NC 4 V SS -4NC < T A < +2NC 22 Input Voltage-Noise Density e N f = khz nv/ Hz Input Voltage Noise.Hz < f < Hz nv P-P Input Current-Noise Density i N f = khz. pa/ Hz Gain-Bandwidth Product GBW MHz Slew Rate SR A V = V/V, V OUT = 2V P-P.7 V/Fs Capacitive Loading C L No sustained oscillation, A V = V/V 4 pf Total Harmonic Distortion Plus Noise EMI Rejection Ratio THD+N V OUT = 2V P-P, A V = +V/V, f = khz - EMIRR V RF_PEAK = mv f = 4MHz 7 f = 9MHz 78 f = 8MHz 8 f = 24MHz 9 Note 2: All devices are % production tested at T A = +2NC. Temperature limits are guaranteed by design. Note 3: Guaranteed by design. Note 4: At IN+ and IN-. Defined as 2log (V RF_PEAK /δv OS ). FV pa pa mv 4

5 36V, Precision, Low-Power, 9µA, Dual Op Amp (T (V A DD = = +2 C, V, Vunless SS = V, otherwise V IN+ = Vnoted.) IN- = V DD /2, R L = kω to V DD /2. Typical values are at T A = +2 C.) OCCURANCE (%) INPUT OFFSET VOLTAGE HISTOGRAM INPUT OFFSET VOLTAGE (µv) MAX44248 toc OCCURANCE (%) INPUT OFFSET VOLTAGE DRIFT INPUT OFFSET VOLTAGE DRIFT (nv/ C) Typical Operating Characteristics MAX44248 toc2 SUPPLY CURRENT (µa) SUPPLY CURRENT vs. SUPPLY VOLTAGE SUPPLY VOLTAGE (V) MAX44248 toc3 SUPPLY CURRENT (µa) SUPPLY CURRENT vs. TEMPERATURE MAX44248 toc4 OFFSET VOLTAGE (µv) INPUT OFFSET VOLTAGE vs. COMMON-MODE VOLTAGE MAX44248 toc OFFSET VOLTAGE (µv) INPUT OFFSET VOLTAGE VS. TEMPERATURE MAX44248 toc TEMPERATURE ( C) COMMON-MODE VOLTAGE (V) TEMPERATURE ( C) INPUT BIAS CURRENT (pa) INPUT BIAS CURRENT VS. COMMON-MODE VOLTAGE MAX44248 toc7 INPUT BIAS CURRENT (pa) INPUT BIAS CURRENT vs. TEMPERATURE MAX44248 toc COMMON-MODE VOLTAGE (V) TEMPERATURE ( C)

6 36V, Precision, Low-Power, 9µA, Dual Op Amp Typical Operating Characteristics (continued) (V DD = V, V SS = V, V IN+ = V IN- = V DD /2, R L = kω to V DD /2. Typical values are at T A = +2 C.) CMRR () COMMON-MODE REJECTION RATIO vs. FREQUENCY MAX44248 toc9 CMRR () COMMON-MODE REJECTION RATIO vs. TEMPERATURE MAX44248 toc PSRR () POWER-SUPPLY REJECTION RATIO vs. FREQUENCY MAX44248 toc VDD - VOUT (mv) -4 k k k M OUTPUT VOLTAGE HIGH vs. TEMPERATURE TEMPERATURE ( C) MAX44248 toc2 VOUT - VSS (mv) TEMPERATURE ( C) OUTPUT VOLTAGE LOW vs. TEMPERATURE TEMPERATURE ( C) MAX44248 toc3 VDD - VOUT (mv) -6 k k k M OUTPUT VOLTAGE HIGH vs. SOURCE CURRENT. SOURCE CURRENT (ma) MAX44248 toc4 VOUT - VSS (mv) OUTPUT VOLTAGE LOW vs. SINK CURRENT. SINK CURRENT (ma) MAX44248 toc INPUT VOLTAGE NOISE (nv/ Hz) INPUT VOLTAGE NOISE vs. FREQUENCY k k k MAX44248 toc6 6

7 36V, Precision, Low-Power, 9µA, Dual Op Amp Typical Operating Characteristics (continued) (V DD = V, V SS = V, V IN+ = V IN- = V DD /2, R L = kω to V DD /2. Typical values are at T A = +2 C.) 4nV/div INPUT VOLTAGE.Hz TO Hz NOISE MAX44248 toc7 INPUT-CURRENT NOISE (pa/ Hz) INPUT CURRENT NOISE vs. FREQUENCY MAX44248 toc8 SMALL-SIGNAL GAIN () SMALL-SIGNAL GAIN vs. FREQUENCY MAX44248 toc9-2 s/div k k k -4. k k k M LARGE-SIGNAL GAIN () LARGE-SIGNAL GAIN vs. FREQUENCY MAX44248 toc2 V IN mv/div V OUT mv/div SMALL-SIGNAL STEP RESPONSE MAX44248 toc2 V IN 2V/div V OUT mv/div LARGE-SIGNAL STEP RESPONSE MAX44248 toc k k k M 4µs/div 4µs/div V DD V/div POWER-UP TIME MAX44248 toc TOTAL HARMONIC DISTORTION vs. FREQUENCY R LOAD = ki MAX44248 toc24 V OUT 2V/div THD () R LOAD = 6I -2 R LOAD = ki 2µs/div -4 k k k 7

8 36V, Precision, Low-Power, 9µA, Dual Op Amp Typical Operating Characteristics (continued) (V DD = V, V SS = V, V IN+ = V IN- = V DD /2, R L = kω to V DD /2. Typical values are at T A = +2 C.) RESISTIVE LOAD (I) k k OUTPUT STABILITY vs. CAPACITIVE LOAD STABLE UNSTABLE MAX44248 toc2 ISOLATION RESISTANCE (I) k k OUTPUT STABILITY vs. ISOLATION RESISTANCE STABLE UNSTABLE MAX44248 toc26 CROSSTALK (),, CAPACITIVE LOAD (pf) CROSSTALK vs. FREQUENCY k k k M MAX44248 toc27 OUTPUT IMPEDANCE (I),, CAPACITIVE LOAD (pf) OUTPUT IMPEDANCE vs. FREQUENCY k k k M MAX44248 toc28 2 EMIRR vs. FREQUENCY MAX44248 toc29 8 EMIRR () 6 4 2,, FREQUENCY (MHz) 8

9 36V, Precision, Low-Power, 9µA, Dual Op Amp Pin Configurations TOP VIEW OUTA INA- 2 + MAX V DD OUTB V DD OUTB INB- INB+ OUTA INA- INA+ V SS MAX INA+ 3 6 INB- µmax V SS 4 INB+ SO Pin Description PIN SO µmax NAME FUNCTION OUTA Channel A Output 2 2 INA- Channel A Negative Input 3 3 INA+ Channel A Positive Input 4 4 V SS Negative Supply Voltage INB+ Channel B Positive Input 6 6 INB- Channel B Negative Input 7 7 OUTB Channel B Output 8 8 V DD Positive Supply Voltage 9

10 36V, Precision, Low-Power, 9µA, Dual Op Amp Detailed Description The MAX44248 is a high-precision amplifier that has a less than 2FV (typ) input-referred offset and low input voltage-noise density at Hz. /f noise, in fact, is eliminated to improve the performance in low-frequency applications. These characteristics are achieved through an auto-zeroing technique that cancels the input offset voltage and /f noise of the amplifier. External Noise Suppression in EMI Form The device has input EMI filters to prevent effects of radio frequency interference on the output. The EMI filters comprise passive devices that present significant higher impedance to higher frequency signals. See the EMIRR vs. Frequency graph in the Typical Operating Characteristics section for details. High Supply Voltage Range The device features 9µA current consumption per channel and a voltage supply range from either 2.7V to 36V single supply or ±.3V to ±8V split supply. Applications Information The device is an ultra-high precision operational amplifier with a high supply voltage range designed for load cell, medical instrumentation, and precision instrument applications. 4 2mA Current-Loop Communication Industrial environments typically have a large amount of broadcast electromagnetic interference (EMI) from highvoltage transients and switching motors. This combined with long cables for sensor communication leads to high-voltage noise on communication lines. Current-Loop communication is resistant to this noise because the EMI induced current is low. This configuration also allows for low-power sensor applications to be powered from the communication lines. The Typical Operating Circuit shows how the device can be used to make a current loop driver. The circuit uses low-power components such as the MAX44248 op amp, the 6-bit MAX26 DAC, and the high-precision 6µA-only MAX633 reference. In this circuit, both the DAC and the reference are referred to the local ground. The MAX44248 op-amp inputs are capable of swinging to the negative supply (which is the local ground in this case). R3 acts as a current mirror with R SENSE. Therefore, if R SENSE = Ω (i.e. 2mA will drop V) and if the current through R3 is μa when I OUT is 2mA (.% error) then R3 = kω. R is chosen along with the reference voltage to provide the 4mA offset. R2 = 2kΩ for 2mA full scale or R2 = 64kΩ for 2% overrange. R SENSE is ratiometric with R3, R independently sets the offset current and R2 independently sets the DAC scaling. Driving High-Performance ADCs The MAX44248 s low input offset voltage and low noise make this amplifier ideal for ADC buffering. Weight scale applications require a low-noise, precision amplifier in front of an ADC. Figure details an example of a load cell and amplifier driven from the same V supply, along with a 6-bit delta sigma ADC such as the MAX2. The MAX2 is an ultra-low-power (< 3FA, max active current), high-resolution, serial output ADC. It provides the highest resolution per unit power in the industry and is optimized for applications that require very high dynamic range with low power such as sensors on a 4 2mA industrial control loop. The device provides a high-accuracy internal oscillator that requires no external components.

11 36V, Precision, Low-Power, 9µA, Dual Op Amp Layout Guidelines The MAX44248 features ultra-low voltage and noise. Therefore, to get optimum performance follow the layout guidelines. Avoid temperature tradients at the junction of two dissimilar metals. The most common dissimilar metals used on a PCB are solder-to-component lead and solder-to-board trace. Dissimilar metals create a local thermocouple. A variation in temperature across the board can cause an additional offset due to Seebeck effect at the solder junctions. To minimize the Seebeck effect, place the amplifier away from potential heat sources on the board, if possible. Orient the resistors such that both the ends are heated equally. It is a good practice to match the input signal path to ensure that the type and number of thermoelectric juntions remain the same. For example, consider using dummy ω resistors oriented in such a way that the thermoelectric source, due to the real resistors in the signal path, are cancelled. It is recommended to flood the PCB with ground plane. The ground plane ensures that heat is distributed uniformly reducing the potential offset voltage degradation due to Seebeck effect. V MAX44248 V AMP A V V DD R G R F R F V DD V IN+ MAX2 V IN- V SS OUTPUT MICRO CONTROLLER AMP B MAX44248 Figure. Weight Application

12 36V, Precision, Low-Power, 9µA, Dual Op Amp PROCESS: BiCMOS Chip Information Ordering Information PART TEMP RANGE PIN-PACKAGE MAX44248AUA+ -4NC to +2NC 8 FMAX MAX44248ASA+ -4NC to +2NC 8 SO 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. 8 SO S μmax U Denotes a lead(pb)-free/rohs-compliant package. 2

13 36V, Precision, Low-Power, 9µA, Dual Op Amp Revision History REVISION NUMBER REVISION DATE DESCRIPTION PAGES CHANGED 7/2 Initial release 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. 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. 6 Rio Robles, San Jose, CA 934 USA The Maxim logo and are trademarks of Products, Inc.