MAX44267 General Description The MAX44267 precision, low-noise, low-drift dual operational amplifier offers true-zero output that allows the output to cross zero maximizing the dynamic range of an ADC and increasing resolution. In addition, the input common-mode range extends from +13.5V down to -12V. The MAX44267 integrates charge-pump circuitry that generates the negative voltage rail in conjunction with external capacitors. This allows the amplifier to operate from a single +4.5V to +15V power supply, but it is as effective as a normal dual-rail 4.5V to 15V amplifier. The architecture eliminates the need for a negative power-supply rail, saving system cost and size. The MAX44267 is unity-gain stable with a gain-bandwidth product of 5MHz. The device features low offset voltage of 50V (max), drift of 0.4V/C (max), and 200nVP-P noise from 0.1Hz to 10Hz. The low offset and noise specifications and wide input common-mode range make the device ideal for sensor transmitters and interfaces. Varying the external charge pump capacitors enables the charge-pump noise to be minimized. The MAX44267 is part of a family of signal chain ICs including amplifiers, multiplexers and ADCs. These ICs eliminate the need for a negative supply to the multiplexer, amplifier and ADC, saving space and cost. See the Typical Application Circuit and Table 1 for more information. See the MAX44247 for the same amplifier with internal charge-pump capacitors in a small 8-pin MAX(R) package. The MAX44267 is available in a 14-pin TSSOP package and is specified over the -40C to +125C operating temperature range. Ordering Information appears at end of data sheet. MAX is a registered trademark of Maxim Integrated Products, Inc. +15V Single-Supply, Dual Op Amp with 10V Output Range Benefits and Features True Bipolar Output Greater than 10V from a Single +15V Supply Eliminates Space and Cost of Negative Power Supply * True Zero Output from a Single Supply High-Accuracy Sensing Over Temperature * Low Input VOS: 50V (max) * Low 0.4V/C (max) of Offset Drift 9nV/Hz Low Input Noise at 1kHz Provides Wide ADC Dynamic Range 5MHz Gain-Bandwidth Product Provides Wide Frequency Input Range Low 2.4mA (max) Quiescent Current Enables Lower Power Dissipation and Cooler Operation Integrated EMI Filter Reduces Sensitivity to Motors and Other High-Frequency Noise Generators 14-Pin TSSOP Package with External Charge-Pump Capacitors Enables Noise Optimization Applications PLC Analog I/O Modules Sensor Interfaces Pressure Sensors Bridge Sensors Analog Level Shifting/Conditioning Block Diagram AMPLIFIER A CFILT + 1 INA- 2 INA+ 3 12 4 11 INB- 10 INB+ VDD CPVDD GND 5 CPGND 6 VSS 7 CP CBYPASS 13 CPVSS 9 CN 8 MAX44267 CFLY 19-7455; Rev 0; 11/14 14 OUTA OUTB AMPLIFIER B CHOLD MAX44267 +15V Single-Supply, Dual Op Amp with 10V Output Range Absolute Maximum Ratings VDD to GND........................................................-0.3V to +16.5V CPVDD to GND...................................................-0.3V to +16.5V CP, CN, CPVSS, VSS Input Current ................................20mA Common-Mode Input Voltage.... (-VDD - 0.3V) to (+VDD + 0.3V) Differential Input Current...................................................20mA Differential Input Voltage (Note 1)..........................................1V OUTA, OUTB to GND................ (-VDD - 0.3V) to (+VDD + 0.3V) Short-Circuit Duration, OUTA, OUTB to either Supply Rail..... 1s Continuous Power Dissipation (TA = +70C) 14-Pin TSSOP (derate 10mW/C above +70C).......796.8mW Operating Temperature Range.......................... -40C to +125C Junction Temperature.......................................................+150C Storage Temperature Range..............................-65C to +150C Lead Temperature (soldering, 10s).................................. +300C Soldering Temperature (reflow)........................................+260C Note 1: The amplifier inputs are connected by internal back-to-back clamp diodes. In order to minimize noise in the input stage, current-limiting resistors are not used. If differential input voltages exceeding 1V are applied, limit input current to 20mA. Package Thermal Characteristics (Note 2) TSSOP Junction-to-Ambient Thermal Resistance (JA)......100.4C/W Junction-to-Case Thermal Resistance (JC)................30C/W Note 2: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial. 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 (VDD = VCPVDD = 15V, VGND = 0V, VCM = GND, RL = 5k to GND, CFLY = 0.022F, CHOLD = 0.1F, CFILT = 0.1F, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 3) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 4.5 15.5 V 4.5 15.5 V DC SPECIFICATIONS Power-Supply Voltage Input Range VDD Charge-Pump Supply Voltage Input Range (Note 4) CPVDD Charge-Pump Negative Supply Output CPVSS Filtered Negative Supply Output VSS Power-Supply Rejection Ratio PSRR Total Quiescent Current IDD Input Common-Mode Range VCM Common-Mode Rejection Ratio www.maximintegrated.com CMRR Guaranteed by PSRR VDD = 15V, RL = -14.8 VDD = 5V, RL = -4.8 VDD = 15V, RL = 5k -13 VDD = 5V, RL = 5k -3.6 +4.5V VDD +15.5V RL = TA = +25C 117 -40C TA +125C 112 TA = +25C V V 137 dB 2.4 -40C TA +125C 3.6 4.0 Guaranteed by CMRR test VDD = 15V -12.0 +13.5 VDD = 5V -2.0 +3.5 VDD = 15V, VCM = -12V to +13.5V TA = +25C 138 -40C TA +125C 122 TA = +25C 125 -40C TA +125C 118 VDD = 5V, VCM = -2V to +3.5V 150 140 mA V dB dB Maxim Integrated 2 MAX44267 +15V Single-Supply, Dual Op Amp with 10V Output Range Electrical Characteristics (continued) (VDD = VCPVDD = 15V, VGND = 0V, VCM = GND, RL = 5k to GND, CFLY = 0.022F, CHOLD = 0.1F, CFILT = 0.1F, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 3) PARAMETER Input Offset Voltage Input Offset Voltage Drift (Note 5) Input Bias Current Input Offset Current Open-Loop Gain Input Resistance SYMBOL VOS TCVOS IB IOS AVOL CONDITIONS MIN TA = +25C IOUT Output Voltage Swing High (VOUT to GND) VOH Output Voltage Swing Low (VOUT to GND) VOL MAX 4 45 -40C TA +125C 50 -40C TA +125C 0.1 0.4 TA = +25C 0.5 1.5 -40C TA +125C 2.5 TA = +25C 0.3 1.0 -40C TA +125C 2.0 TA = +25C VDD = 15V, -11V VOUT +13.5V -40C TA +125C VDD = 5V, -1.3V VOUT +3.5V 136 TA = +25C 130 -40C TA +125C 121 UNITS V V/C nA nA 145 129 RIN Maximum Output Current TYP dB 140 50 Sinking 17 Sourcing 36 M mA VDD = 15V, RL = 5k, both channels driven 13.8 14.8 VDD = 5V, RL = 5k, both channels driven 3.8 4.9 VDD = 15V, RL = 5k, both channels driven -11.3 -12.7 V VDD = 5V, RL = 5k,both channels driven -1.5 -3.5 V V AC SPECIFICATIONS Input Voltage-Noise Density eN Input Voltage Noise Input Current-Noise Density Gain-Bandwidth Product Slew Rate Total Harmonic Distortion Capacitive Loading Charge-Pump Frequency iN f = 1kHz 9 nV/Hz 0.1Hz < f < 10Hz 200 nVP-P f = 1kHz 200 fA/Hz GBW 5 MHz SR 3 V/s THD f = 1kHz, VOUT = 2VP-P, AV = +1V/V -100 dB CL No sustained oscillation, AV = +1V/V 300 pF 500 kHz 2 mV -100 dB 1 s fOSC Charge-Pump Feedthrough Crosstalk Settling Time Xtalk tS f = 1kHz Note 3: All devices are 100% production tested at TA = +25C. Temperature limits are guaranteed by design. Note 4: CPVDD voltage must be equal to VDD voltage. Connect CPVDD to VDD. Note 5: Parameter is guaranteed by design. www.maximintegrated.com Maxim Integrated 3 MAX44267 +15V Single-Supply, Dual Op Amp with 10V Output Range Typical Operating Characteristics (VDD = VCPVDD = 15V, VGND = VCPGND = 0V, VCM = 0V, CFLY = 0.022F, CHOLD = 0.1F, CFILT = 0.1F, RL = 5k and CL = 10pF to GND, TA = +25C, unless otherwise noted.) TOTAL SUPPLY CURRENT vs. TEMPERATURE TOTAL SUPPLY CURRENT vs. VDD toc01 2.5 3 2.45 2.6 VDD = +15V 2.4 2.3 2.25 2.2 2.15 VCPVSS, VSS (V) 2.35 IDD (mA) SUPPLY CURRENT (mA) 1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12 -13 -14 -15 -16 -17 2.8 2.4 2.2 2 1.8 1.6 2.1 1.4 VDD = +5V 2.05 2 CPVSS AND VSS vs. VDD toc02 1.2 -50 -25 0 25 50 75 100 1 125 TEMPERATURE (C) 7.5 9 10.5 VDD (V) 12 13.5 -14 VSS -14.5 -25 0 4.5 6 7.5 9 10.5 VDD (V) 12 13.5 15 toc2d OP AMPS, VSS AND CPVSS UNLOADED -4 VSS CPVSS 25 50 75 100 -5 125 -50 -25 0 25 50 75 100 125 TEMPERATURE (C) INPUT OFFSET VOLTAGE HISTOGRAM INPUT BIAS CURRENT vs. TEMPERATURE toc03 60 toc04 0 -50 50 INPUT BIAS CURRENT (pA) PERCENT OCCURRENCE (%) CPVSS CPVSS AND VSS vs. TEMPERATURE (VDD = 5V) TEMPERATURE (C) 40 30 20 -100 IB- -150 -200 -250 -300 -350 IB+ -400 10 0 VSS -4.5 CPVSS -50 15 -3.5 OP AMPS, VSS AND CPVSS UNLOADED VCPVSS, VSS (V) VCPVSS, VSS (V) 6 CPVSS AND VSS vs. TEMPERATURE (VDD = 15V) toc2c -13.5 -15 4.5 toc2b OP AMPS, VSS AND CPVSS UNLOADED -450 -4 -3 -2 -1 0 1 2 OFFSET VOLTAGE (V) www.maximintegrated.com 3 4 -500 -50 -25 0 25 50 75 100 125 TEMPERATURE (C) Maxim Integrated 4 MAX44267 +15V Single-Supply, Dual Op Amp with 10V Output Range Typical Operating Characteristics (continued) (VDD = VCPVDD = 15V, VGND = VCPGND = 0V, VCM = 0V, CFLY = 0.022F, CHOLD = 0.1F, CFILT = 0.1F, RL = 5k and CL = 10pF to GND, TA = +25C, unless otherwise noted.) INPUT OFFSET VOLTAGE vs. TEMPERATURE INPUT OFFSET CURRENT vs. TEMPERATURE toc4b 150 10 toc06 0 -50 -100 -150 -200 -250 -300 -350 6 4 2 0 -2 -4 -6 -400 -8 -450 -10 -50 -25 0 25 50 75 100 125 VOLTAGE NOISE DENSITY (nV/Hz) 8 50 INPUT OFFSET VOLTAGE (V) INPUT OFFSET CURRENT (pA) 100 INPUT VOLTAGE-NOISE DENSITY vs. FREQUENCY toc05 TEMPERATURE (C) -50 -25 0 25 50 75 100 1000 100 10 1 125 TEMPERATURE (C) 1 10 100 1000 10000 100000 FREQUENCY (Hz) INPUT CURRENT-NOISE DENSITY vs. FREQUENCY toc07 0.1Hz TO 10Hz PEAK-TO-PEAK NOISE toc08 CURRENT-NOISE DENSITY (fA/Hz) 10000 1000 100nV/div 100 10 1 10 100 1000 10000 100000 1s/div 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 -110 -120 -130 -140 PSRR vs. FREQUENCY toc09 CMRR (dB) PSRR (dB) FREQUENCY (Hz) 0.01 0.1 1 10 100 FREQUENCY (kHz) www.maximintegrated.com 1000 10000 -20 -30 -40 -50 -60 -70 -80 -90 -100 -110 -120 -130 -140 -150 CMRR vs. FREQUENCY toc10 VDD = 15V 0.01 0.1 1 10 100 1000 10000 FREQUENCY (kHz) Maxim Integrated 5 MAX44267 +15V Single-Supply, Dual Op Amp with 10V Output Range Typical Operating Characteristics (continued) -20 -30 -40 -50 -60 -70 -80 -90 -100 -110 -120 -130 -140 -150 SMALL-SIGNAL GAIN vs. FREQUENCY CMRR vs. FREQUENCY toc11 toc12 5 VDD = 5V 0 SMALL-SIGNAL GAIN (dB) CMRR (dB) (VDD = VCPVDD = 15V, VGND = VCPGND = 0V, VCM = 0V, CFLY = 0.022F, CHOLD = 0.1F, CFILT = 0.1F, RL = 5k and CL = 10pF to GND, TA = +25C, unless otherwise noted.) -5 -10 -15 -20 -25 VIN = 100mVP-P GAIN = 1V/V -30 0.01 0.1 1 10 100 1000 10000 -35 0.1 1 10 100 1000 10000 100000 SMALL-SIGNAL STEP RESPONSE (G = -1V/V, VIN = 100mVPP, CL = 10pF) LARGE-SIGNAL GAIN vs. FREQUENCY toc13 5 0.01 FREQUENCY (kHz) FREQUENCY (kHz) toc14 LARGE-SIGNAL GAIN (dB) 0 -5 VIN 100mV/div -10 -15 -20 VOUT -25 -30 -35 100mV/div VIN = 2VP-P GAIN = 1V/V 0.01 0.1 1 10 100 1s/div 1000 10000 100000 FREQUENCY (kHz) SMALL-SIGNAL STEP RESPONSE (G = -1V/V, VIN = 100mVPP, CL = 100pF) SMALL-SIGNAL STEP RESPONSE (G = +1V/V, VIN = 100mVPP, CL = 10pF) toc15 VIN 100mV/div VOUT 100mV/div 1s/div www.maximintegrated.com toc16 VIN 100mV/div VOUT 100mV/div 1s/div Maxim Integrated 6 MAX44267 +15V Single-Supply, Dual Op Amp with 10V Output Range Typical Operating Characteristics (continued) (VDD = VCPVDD = 15V, VGND = VCPGND = 0V, VCM = 0V, CFLY = 0.022F, CHOLD = 0.1F, CFILT = 0.1F, RL = 5k and CL = 10pF to GND, TA = +25C, unless otherwise noted.) SMALL-SIGNAL STEP RESPONSE (G = +1V/V, VIN = 100mVPP, CL = 100pF) LARGE-SIGNAL STEP RESPONSE (G = -1V/V, VIN = 10VPP, CL = 100pF) toc17 VIN 100mV/div VOUT 100mV/div toc18 VIN 10V/div VOUT 10V/div 100 IN SERIES WITH VIN 1s/div LARGE-SIGNAL STEP RESPONSE (G = +1V/V, VIN = 10VPP, CL = 100pF) 20s/div PERCENT OVERSHOOT vs. CAPACITIVE LOAD toc19 toc20 50 GAIN = +1V/V, VIN = 100mV, 1kHz RL = 5k 10V/div 10V/div VOUT PERCENT OVERSHOOT (%) 40 VIN 30 NEGATIVE 20 POSITIVE 10 100 IN SERIES WITH VIN 0 20s/div 0 50 100 150 200 250 300 350 CAPACITIVE LOAD (pF) NEGATIVE OVERLOAD RECOVERY (G = -10V/V, CL = 10pF) VIN 0V VOUT toc22 2V -2V VIN 0V 15V VOUT 0V 0V 1s/div www.maximintegrated.com POSITIVE OVERLOAD RECOVERY (G = -10V/V, CL = 10pF) toc21 -15V 1s/div Maxim Integrated 7 MAX44267 +15V Single-Supply, Dual Op Amp with 10V Output Range Typical Operating Characteristics (continued) (VDD = VCPVDD = 15V, VGND = VCPGND = 0V, VCM = 0V, CFLY = 0.022F, CHOLD = 0.1F, CFILT = 0.1F, RL = 5k and CL = 10pF to GND, TA = +25C, unless otherwise noted.) NO PHASE REVERSAL (VDD = 15V, G = +1V/V, VIN = 29VP-P) NO PHASE REVERSAL (VDD = 5V, G = +1V/V, VIN = 9VP-P) toc23 VIN toc24 10V/div VOUT VIN 2V/div VOUT 2V/div 10V/div 200s/div 10s/div toc25 EMIRR vs. FREQUENCY 80 toc26 70 AMPS, SS AND OP OP AMPS, VSSVAND SS UNLOADED CPVCPV SS UNLOADED 60 5V/div VDD 1V/div VOUTA VOUTB 1V/div EMIRR (dB) TURN-ON TRANSIENT (VIN_+ = 500mV) 50 40 30 20 IDD 10 40mA/div 0 100s/div 10 100 1000 10000 FREQUENCY (MHz) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT AMPLITUDE TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY toc27 -20 -20 -30 -30 -40 -40 -50 -60 -70 G = +1V/V, f = 1kHz -50 -60 -70 -80 -80 -90 -90 -100 -100 -110 -110 -120 toc28 0 -10 THD (dB) THD+N (dB) 0 -10 10 100 1000 FREQUENCY (Hz) www.maximintegrated.com 10000 100000 -120 0 5 10 15 20 25 30 OUTPUT AMPLITUDE (V) Maxim Integrated 8 MAX44267 +15V Single-Supply, Dual Op Amp with 10V Output Range Typical Operating Characteristics (continued) (VDD = VCPVDD = 15V, VGND = VCPGND = 0V, VCM = 0V, CFLY = 0.022F, CHOLD = 0.1F, CFILT = 0.1F, RL = 5k and CL = 10pF to GND, TA = +25C, unless otherwise noted.) OUTPUT IMPEDANCE vs. FREQUENCY VOUT HIGH vs. OUTPUT SOURCE CURRENT toc29 2.5 1.5 VOUT HIGH (V) OUTPUT IMPEDANCE () 2 1 0.5 0 0.01 0.1 1 10 100 1000 10000 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 toc30 VOUT_ VDD = 15V AMP_ SOURCING ONLY 0 5 10 15 20 25 ISOURCE (mA) FREQUENCY (kHz) VOUT HIGH vs. OUTPUT SOURCE CURRENT toc31 6 VOUT LOW (V) VOUT HIGH (V) toc32 VOUTA VOUT_ 3 2 VDD = 5V AMP_ SOURCING ONLY 1 0 5 10 15 20 25 ISOURCE (mA) 30 35 -12 -13 VOUTB -14 VDD = 15V AMP A SINKING ONLY (AMP B NOT SINKING) -15 40 0 toc33 14 16 18 20 toc34 6 8 ISINK (mA) 10 -13 -13.2 VDD = 5V AMP A SINKING ONLY (AMP B NOT SINKING) www.maximintegrated.com 12 -13.1 VOUTB 4 10 -12.9 -3 2 8 -12.8 VOUTA 0 6 DRIVING BOTH CHANNELS, VDD = 15V, 5k LOAD TO GND per AMP -12.7 VOUT LOW (V) VOUT LOW (V) -1 -4 4 VOUT LOW vs. TEMPERATURE -12.5 -12.6 -2 2 ISINK (mA) VOUT LOW vs. OUTPUT SINK CURRENT 0 -5 40 -11 4 0 35 VOUT LOW vs. OUTPUT SINK CURRENT -10 5 30 AMP B AMP A -13.3 -13.4 12 14 -13.5 -50 -25 0 25 50 75 100 125 TEMPERATURE (C) Maxim Integrated 9 MAX44267 +15V Single-Supply, Dual Op Amp with 10V Output Range Typical Operating Characteristics (continued) (VDD = VCPVDD = 15V, VGND = VCPGND = 0V, VCM = 0V, CFLY = 0.022F, CHOLD = 0.1F, CFILT = 0.1F, RL = 5k and CL = 10pF to GND, TA = +25C, unless otherwise noted.) VOUT LOW vs. TEMPERATURE -3.3 toc35 VOUT HIGH vs. TEMPERATURE 15 DRIVING BOTH CHANNELS, VDD = 5V, 5k LOAD TO GND per AMP toc36 DRIVING BOTH CHANNELS, VDD = 15V, 5k LOAD TO GND per AMP -3.4 VOH (V) VOUT LOW (V) 14.9 -3.5 AMP A 14.8 -3.6 AMP B AMP A AMP B -3.7 -50 -25 0 25 50 75 100 14.7 125 -50 -25 TEMPERATURE (C) toc37 0 25 50 75 toc38 1 UNSTABLE 0.1 STABLE 100 125 0.001 100 1000 STABILITY vs. CAPACITIVE LOAD AND ISOLATION RESISTANCE toc39 10 0.1 CROSSTALK (dB) RISO () STABLE UNSTABLE 1 100 1000 10000 CAPACITIVE LOAD (pF) www.maximintegrated.com 10000 CAPACITIVE LOAD (pF) TEMPERATURE (C) 100 125 0.01 AMP B -25 100 100 RESISTIVE LOAD (k) VOH (V) AMP A -50 75 10 5 4.8 50 STABILITY vs. CAPACITIVE LOAD AND ISOLATION RESISTANCE DRIVING BOTH CHANNELS, VDD = 5V, 5k LOAD TO GND per AMP 4.9 25 TEMPERATURE (C) VOUT HIGH vs. TEMPERATURE 5.1 0 100000 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 -110 -120 -130 -140 CROSSTALK vs. FREQUENCY 0.01 0.1 1 10 100 1000 toc40 10000 FREQUENCY (kHz) Maxim Integrated 10 MAX44267 +15V Single-Supply, Dual Op Amp with 10V Output Range Pin Configuration TOP VIEW + 14 VDD 13 CPVDD 12 OUTB 11 INB- 5 10 INB+ VSS 6 9 CPVSS CP 7 8 CN OUTA 1 INA- 2 INA+ 3 GND 4 CPGND MAX44267 TSSOP Pin Description PIN NAME 1 OUTA 2 INA- Channel A Negative Input 3 INA+ Channel A Positive Input 4 GND Ground. Connect GND to a solid ground plane. 5 CPGND 6 VSS Filtered Negative Supply Output. Bypass VSS with a low-ESR capacitor (CFILT = 1F) to GND. 7 CP Charge-Pump Positive Capacitor Connection. Capacitor connection only to CN. Do not connect any voltage on CP or CN. Connect a low-ESR capacitor (CFLY = 0.022F) between CP and CN. 8 CN Charge-Pump Negative Capacitor Connection. Capacitor connection only to CP. Do not connect any voltage on CN or CP. Connect a low-ESR capacitor (CFLY = 0.022F) between CP and CN. 9 CPVSS 10 INB+ Channel B Positive Input 11 INB- Channel B Negative Input 12 OUTB 13 CPVDD 14 VDD www.maximintegrated.com FUNCTION Channel A Output Charge-Pump Ground. Connect CPGND to GND. Charge Pump Negative Supply Output. Bypass CPVSS with a 0.1F capacitor to CPGND. Channel B Output Charge-Pump Supply Voltage Input. Connect CPVDD to VDD. Bypass CPVDD with a 0.1F capacitor to GND. Device Supply Voltage Input. Bypass VDD with a 0.1F capacitor to GND. Maxim Integrated 11 MAX44267 +15V Single-Supply, Dual Op Amp with 10V Output Range Detailed Description The MAX44267 is a high-precision amplifier that provides less than 50V of maximum input-referred offset and low 1/f noise. These characteristics are achieved by using a combination of proprietary auto-zeroing and chopperstabilized techniques. This combination of auto-zeroing and chopping ensures that these amplifiers give all the benefits of zero-drift amplifiers, while still ensuring low noise, minimizing chopper spikes, and providing wide bandwidth. Common Internal Charge Pump The MAX44267's integrated charge pump produces a negative voltage rail (VSS) that is common to both amplifiers (see Figure 1 for external capacitor connections). The device consumes a total of 4mA (max) of quiescent current (including both the op amps and the charge-pump operation). negative supply voltage, affecting its driving capability when sinking current. Sinking beyond typically 17mA per channel will result in reduced swing in the negative direction and increased ripple affecting both outputs and degrading output accuracy and performance of both amplifiers. The output VSS negative supply is common to both amplifier channels. Loading the output of one channel beyond the recommended value will affect the second amplifier channel as mentioned above. The total loading of both channels must be kept below 17mA. If one channel is minimally loaded, for example, only sinking 100A, the other channel may sink 16.9mA. As shown in Figure 2, when using VDD of +15V the VSS output will be around -13.6V (typ) at no load. As amplifier A is sinking, it causes the VSS rail to rise and this is reflected in VOUTB. The VSS generator acts as a negative supply for the MAX44267, and has limited sink current capability. Attempting to load more than its capability will reduce the VOUT LOW vs. OUTPUT SINK CURRENT -10 -11 CFILT 2 VDD 14 INA- CPVDD 13 3 INA+ OUTB 12 4 GND INB- 11 5 CPGND INB+ 10 6 VSS 7 CP CPVSS 9 CN 8 MAX44267 CFLY VOUTA CBYPASS AMPLIFIER B VOUT LOW (V) AMPLIFIER A 1 + OUTA -12 -13 VOUTB -14 VDD = 15V AMP A SINKING ONLY (AMP B NOT SINKING) CHOLD -15 0 2 4 6 8 10 12 14 16 18 20 ISINK (mA) Figure 1. External Capacitor Connections www.maximintegrated.com Figure 2. VOUT LOW vs. OUTPUT SINK CURRENT Maxim Integrated 12 MAX44267 +15V Single-Supply, Dual Op Amp with 10V Output Range ESD Networks The MAX44267 output swing can be well below 0V while all the other circuitry on the board may have 0V as its most negative terminal. Since almost all modern integrated circuits protect their inputs with a network of diode clamps to their power rails, it is possible to discover the driven circuit is clamping the MAX44267's output (Figure 3). Maxim Integrated has many products that have inputs that can be driven Beyond the Rails: ADCs, multiplexers and current-sensing amplifiers. Other circuitry should be designed such that the MAX44267's output will not be clamped by another circuit's ESD network. A common solution to this problem is to arrange that the output is level-shifted as well as amplified or conditioned by the MAX44267. Be sure not to exceed the absolute maximum ratings on any devices surrounding the MAX44267 amplifier. Capacitor Selection The MAX44267 requires three external capacitors (CFLY, CHOLD, and CFILT) to generate the VSS negative supply rail. The charge-pump output resistance is a function of the ESR of CFLY, CHOLD, and CFILT. To maintain the lowest output resistance, use capacitors with low ESR. Flying Capacitor (CFLY) Increasing the flying capacitor's value reduces the output resistance. Above 0.047F, increasing CFLY's capacitance has negligible effect because internal switch resistance and capacitor ESR then dominate the output resistance. Output Capacitor (CHOLD) Increasing the output capacitor's value reduces the output ripple voltage. Decreasing its ESR reduces both output resistance and ripple. Lower capacitance values can be VDD VDD DRIVEN CIRCUIT ON SINGLE SUPPLY MAX44267 INTERNAL ESD PROTECTION NETWORK Figure 3. Possibility of Clamping the MAX44267 Output via Another Circuit's ESD Network www.maximintegrated.com Maxim Integrated 13 MAX44267 +15V Single-Supply, Dual Op Amp with 10V Output Range used with light loads if higher output ripple can be tolerated. Refer to the following graphs to estimate the peakto-peak ripple for certain sinking current value. CPVSS Bypass Capacitor 6 Bypass the incoming supply (CPVSS) to reduce its AC impedance and the impact of the charge pump's switching noise. Connect a minimum of a 0.1F low-ESR capacitor from CPVSS to CPGND as close as possible to the IC. Low-frequency noise, inherent in all active devices, is inversely proportional to frequency. Charges at the oxidesilicon interface that are trapped-and-released by oxide and PN junction occur at low frequency more often. The MAX44267 eliminates the 1/f noise internally, thus making it an ideal choice for DC or low frequency, high-precision applications. The 1/f noise appears as a slow varying offset voltage and is eliminated by the chopping technique used. Electromagnetic interference (EMI) noise occurs at higher frequency that results in malfunction or degradation of electrical equipment. The ICs have an input EMI filter to avoid the output being affected by radio frequency interference. The EMI filter composed of passive devices presents significant higher impedance to higher frequency. VDD = VCPVDD = 15V CHOLD = CFILT = 0.1F VSS SINKING CURRENT 5 2 0 VSS_RIPPLE 5 4 6 8 ISS_SINK (mA) 10 12 14 Figure 4. IOUTSINK vs. VSS_RIPPLE (CFLY = 0.022F, CHOLD = CFILT = 0.1F) www.maximintegrated.com 6 8 10 12 14 VDD = VCPVDD = 15V CFLY = 0.022F CHOLD = CFILT = 0.1F VSS SINKING CURRENT 15 1 2 4 TOTAL IDD vs. ISS OUTPUT SINK CURRENT 20 VOUTA_RIPPLE 2 Figure 5. IOUTSINK vs. VSS_RIPPLE (CFLY = 0.047F, CHOLD = CFILT = 0.1F) 10 0 0 ISS_SINK (mA) 2 0 VOUTA_RIPPLE 30 VOUTB_RIPPLE 3 3 25 4 VSS_RIPPLE VOUTB_RIPPLE 1 IDD (mA) VSS_RIPPLE (mVP-P) 4 VSS_RIPPLE vs. ISS OUTPUT SINK CURRENT (CFLY = 0.022F) 6 VDD = VCPVDD = 15V CHOLD = CFILT = 0.1F VSS SINKING CURRENT 5 VSS_RIPPLE (mVPP) Noise Suppression VSS_RIPPLE vs. ISS OUTPUT SINK CURRENT (CFLY = 0.047F) 0 0 2 4 6 8 10 12 14 16 18 ISS_SINK (mA) Figure 6. Total Supply Current vs. ISINK Maxim Integrated 14 MAX44267 +15V Single-Supply, Dual Op Amp with 10V Output Range True Zero Output Architecture the output sink current of one or both amplifiers combined, it will lose regulation, limiting output swing in the negative direction. Additionally, if regulation is lost, and the input is forced towards the negative rail, the MAX44267 can enter a latchup condition. This latchup is non-destructive, and the device will recover when the fault conditions are removed. The MAX44267 is unique compared to the majority of operational amplifiers. The MAX44267 contains an internal charge pump that generates a negative voltage rail (VSS), shared by both amplifiers. This allows the amplifier input and output ranges to extend substantially below 0V, while powered from only a single positive supply. VSS output supplies both amplifiers and its output load current. VSS can be used to power external circuitry but the additional load current is seen as additional load by the charge pump. This internally generated negative supply can cause currents to flow in unexpected paths--especially through the electrostatic discharge protection networks found in almost all modern integrated circuits (Figure 7). The MAX44267 is specified with a 5k load on each output channel. This results in a maximum output load current that is well below an overload of the generator, and so the device will not latch up. It is possible to drive even heavier loads, although the total output sink current (of both channels combined) should not be allowed to exceed 15mA peak. (see the VOUT Low vs. Output Sink Current graph in the Typical Operating Characteristics for details). When driving loads that may approach the output's limit, it is recommended that the inputs should be high-impedance sources or add a protective 5k series resistor. Near-Zero Source Impedances The negative voltage generator has a finite current sink capability (typically around 15mA for CFLY = 0.022F, CHOLD = CFILT = 0.1F). If the device is overloaded by 15V CPVDD VDD MAX44267 BIASING VDD AMPLIFIER VSS VDD VSS -5V VERY LOW SOURCE IMPEDANCE OUT_ ON CFILT VSS CPVSS CHARGE PUMP CHOLD CN CP CFLY Figure 7. Possible Latchup Due to Overloading the MAX44267 www.maximintegrated.com Maxim Integrated 15 MAX44267 +15V Single-Supply, Dual Op Amp with 10V Output Range Applications Information uses resistances of 10k in each leg, the noise will be about 24nV/Hz, which is then amplified by 100x, along with the signal to give 2.4V. If the bandwidth is kept down to 100Hz then this is only 24VRMS or about 300VP-P yielding a signal to noise ratio of 68dB. This can of course be improved by averaging the readings over a suitably long period of time with an integral number of 60Hz (50Hz) cycles usually offering both improved resolution and reduced sensitivity to the 60Hz power system. Bridge Measurement Configuration without Instrumentation Amplifier The MAX44267's low input offset voltage and low noise make it ideal for biasing strain gauges (Figure 8). The strain-gauge bridge is most commonly biased from the reference source and the output from the bridge is then at approximately half the reference voltage. In the case of biasing around ground, a negative supply needs to be available. Hence, the bridge is biased at twice the reference voltage and the center is at 0V (to within the offset voltage of the amplifier X1). Doubling the voltage across the bridge doubles its sensitivity, but of course, the downside is twice the current flows. Layout Guidelines The MAX44267 features ultra-low offset voltage and noise, causing the Seebeck effect error to become significant. Therefore, to get optimum performance follow the following layout guidelines: Avoid temperature gradients 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 the 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 good practice to match the input signal path to ensure that the type and number of thermoelectric junctions remain the same. For example, consider using dummy 0 resistors oriented such that the thermoelectric sources due to the real resistors in the signal path is 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. Since the bridge's center is now forced to be at 0V, the node "ip" must also be at 0V when no strain is applied, to within the calibration of zero strain of the bridge. Having controlled the zero bias point, the application can use the second amplifier within the dual MAX44267 to take a very large, direct-coupled gain without the usual risk of common-mode errors causing the output to saturate. A full bridge, as shown, typically produces a differential output with a full scale of approximately 0.1% of the biasing voltage. Doubling the biasing voltage yields a doubling of sensitivity while also removing any common-mode error for the high-gain amplifier. Assuming that RB3 and RB2 are configured to decrease their resistance as the strain increases while RB1 and RB4 increase their resistance, then the full-scale output will be +819.2mV at the output. Capacitor C1 can be sized to roll of any unwanted bandwidth and its associated noise. Assuming the bridge VIN MAX6070 R1 18k VOUT VREF 4.096V VCC R3 180k C1 1nF RB3 RB1 X2 ip 1/2 MAX44267 RB2 RB4 VCC R2 2k X1 1/2 MAX44267 Figure 8. Bridge Measurement Configuration without Instrumentation Amplifier www.maximintegrated.com Maxim Integrated 16 MAX44267 +15V Single-Supply, Dual Op Amp with 10V Output Range Typical Application Circuit 5V SINGLE SUPPLY MAX14778 25V SOURCES R1 R3 VREF MUX A MAX11166 1/2 MAX44267 C1 R2 C2 5V 1/2 MAX44267 5V 25V SOURCES R6 R4 MUX B MAX11166 VREF R5 C4 C3 COMPLETE BEYOND-THE-RAILS SIGNAL CHAIN SOLUTION Table 1. Selector Guide for the Typical Operating Circuit PART NO. FUNCTION VOLTAGE SUPPLY RANGE (V) INPUT VOLTAGE RANGE (V) MAX44267 Precision amplifier +4.5 to +15.5 -12.0 to +13.5 MAX14778 4:1 mux +3 to +5.5 25 MAX14762 2-channel switch +3 to +5.5 25 MAX11167 16-bit ADC +5 5 www.maximintegrated.com Maxim Integrated 17 MAX44267 +15V Single-Supply, Dual Op Amp with 10V Output Range Ordering Information PART TEMP RANGE MAX44267AUD+ -40C to + 125C Chip Information PIN-PACKAGE PROCESS: BiCMOS 14 TSSOP +Denotes a lead(Pb)-free/RoHS-compliant package. Package Information For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. 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 14 TSSOP www.maximintegrated.com PACKAGE OUTLINE NO. CODE U14+1 21-0066 LAND PATTERN NO. 90-0113 Maxim Integrated 18 MAX44267 +15V Single-Supply, Dual Op Amp with 10V Output Range Revision History REVISION NUMBER REVISION DATE 0 11/14 DESCRIPTION Initial release PAGES CHANGED -- For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated's website at www.maximintegrated.com. 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. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. 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