LMP7716MMX

LMP7715/LMP7716 Precision, 17 MHz, Low Noise, CMOS Input Amplifiers May 2006 LMP7715/LMP7716 Single and Dual Precision, 17 MHz, Low Noise, CMOS Input Amplifiers General Description The LMP7715/LMP7716 are single and dual low noise, low offset, CMOS input, rail-to-rail output precision amplifiers with high gain bandwidth products. The LMP7715/LMP7716 are part of the LMP™ precision amplifier family and are ideal for a variety of instrumentation applications. Utilizing a CMOS input stage, the LMP7715/LMP7716 achieve an input bias current of 100 fA, an input referred , and an input offset voltage of voltage noise of 5.8 nV/ less than ± 150 µV. These features make the LMP7715/ LMP7716 superior choices for precision applications. Consuming only 1.15 mA of supply current, the LMP7715 offers a high gain bandwidth product of 17 MHz, enabling accurate amplification at high closed loop gains. The LMP7715/LMP7716 have a supply voltage range of 1.8V to 5.5V, which makes these ideal choices for portable low power applications with low supply voltage requirements. The LMP7715/LMP7716 are built with National’s advanced VIP50 process technology. The LMP7715 is offered in a 5-pin SOT23 package and the LMP7716 is offered in an 8-pin MSOP. Features Unless otherwise noted, typical values at VS = 5V. ± 150 µV (max) n Input offset voltage n Input bias current 100 fA n Input voltage noise 5.8 nV/ n Gain bandwidth product 17 MHz n Supply current (LMP7715) 1.15 mA n Supply current (LMP7716) 1.30 mA n Supply voltage range 1.8V to 5.5V n THD+N @ f = 1 kHz 0.001% n Operating temperature range −40oC to 125˚C n Rail-to-rail output swing n Space saving SOT23 package (LMP7715) n MSOP-8 package (LMP7716) Applications n Active filters and buffers n Sensor interface applications n Transimpedance amplifiers Typical Performance Offset Voltage Distribution Input Referred Voltage Noise 20183622 20183639 LMP™ is a trademark of National Semiconductor Corporation. © 2006 National Semiconductor Corporation DS201836 www.national.com LMP7715/LMP7716 Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. ESD Tolerance (Note 2) Human Body Model Machine Model VIN Differential Supply Voltage (VS = V+ – V−) Voltage on Input/Output Pins Storage Temperature Range Junction Temperature (Note 3) 2000V 200V Soldering Information Infrared or Convection (20 sec) Wave Soldering Lead Temp. (10 sec) 235˚C 260˚C Operating Ratings (Note 1) Temperature Range (Note 3) Supply Voltage (VS = V – V ) 0˚C ≤ TA ≤ 125˚C −40˚C ≤ TA ≤ 125˚C Package Thermal Resistance (θJA(Note 3)) 5-Pin SOT23 8-Pin MSOP 180˚C/W 236˚C/W 1.8V to 5.5V 2.0V to 5.5V + − ± 0.3V 6.0V V+ +0.3V, V− −0.3V −65˚C to 150˚C +150˚C −40˚C to 125˚C 2.5V Electrical Characteristics Unless otherwise specified, all limits are guaranteed for TA = 25˚C, V+ = 2.5V, V− = 0V ,VO = VCM = V+/2. Boldface limits apply at the temperature extremes. Symbol VOS TC VOS IB IOS CMRR PSRR Parameter Input Offset Voltage Input Offset Voltage Drift (Note 6) Input Bias Current Input Offset Current Common Mode Rejection Ratio Power Supply Rejection Ratio LMP7715 LMP7716 VCM = 1V (Notes 7, 8) VCM = 1V (Note 8) 0V ≤ VCM ≤ 1.4V 2.0V ≤ V+ ≤ 5.5V V− = 0V, VCM = 0 1.8V ≤ V+ ≤ 5.5V V− = 0V, VCM = 0 CMVR AVOL Input Common-Mode Voltage Range Large Signal Voltage Gain CMRR ≥ 80 dB CMRR ≥ 78 dB LMP7715, VO = 0.15 to 2.2V RL = 2 kΩ to V+/2 LMP7716, VO = 0.15 to 2.2V RL = 2 kΩ to V+/2 LMP7715, VO = 0.15 to 2.2V RL = 10 kΩ to V+/2 LMP7716, VO = 0.15 to 2.2V RL = 10 kΩ to V+/2 VO Output Swing High RL = 2 kΩ to V+/2 RL = 10 kΩ to V+/2 Output Swing Low RL = 2 kΩ to V+/2 RL = 10 kΩ to V+/2 83 80 85 80 85 −0.3 –0.3 88 82 84 80 92 88 90 86 70 77 60 66 98 92 110 95 25 20 30 15 70 73 60 62 mV from V+ dB Conditions Min (Note 5) Typ (Note 4) Max (Note 5) Units ± 20 –1 –1.75 0.05 0.006 100 100 98 ± 180 ± 480 ±4 50 100 25 50 µV µV/˚C pA pA dB dB 1.5 1.5 V mV www.national.com 2 LMP7715/LMP7716 2.5V Electrical Characteristics Symbol IO Parameter Output Short Circuit Current (Continued) Unless otherwise specified, all limits are guaranteed for TA = 25˚C, V+ = 2.5V, V− = 0V ,VO = VCM = V+/2. Boldface limits apply at the temperature extremes. Conditions Sourcing to V− VIN = 200 mV (Note 9) Sinking to V+ VIN = −200 mV (Note 9) IS Supply Current LMP7715 LMP7716 (per channel) SR GBW en in THD+N Slew Rate Gain Bandwidth Product Input-Referred Voltage Noise Input-Referred Current Noise Total Harmonic Distortion + Noise f = 400 Hz f = 1 kHz f = 1 kHz f = 1 kHz, AV = 1, RL = 100 kΩ VO = 0.9 VPP f = 1 kHz, AV = 1, RL = 600Ω VO = 0.9 VPP AV = +1, Rising (10% to 90%) AV = +1, Falling (90% to 10%) Min (Note 5) 36 30 7.5 5.0 Typ (Note 4) 52 15 0.95 1.10 8.3 10.3 14 6.8 5.8 0.01 0.003 0.004 % 1.30 1.65 1.50 1.85 mA Max (Note 5) Units mA V/µs MHz nV/ pA/ 5V Electrical Characteristics Unless otherwise specified, all limits are guaranteed for TA = 25˚C, V+ = 5V, V− = 0V, VCM = V+/2. Boldface limits apply at the temperature extremes. Symbol VOS TC VOS IB IOS CMRR PSRR Parameter Input Offset Voltage Input Offset Average Drift (Note 6) Input Bias Current Input Offset Current Common Mode Rejection Ratio Power Supply Rejection Ratio LMP7715 LMP7716 (Notes 7, 8) (Note 8) 0V ≤ VCM ≤ 3.7V 2.0V ≤ V+ ≤ 5.5V V− = 0V, VCM = 0 1.8V ≤ V+ ≤ 5.5V V− = 0V, VCM = 0 CMVR AVOL Input Common-Mode Voltage Range Large Signal Voltage Gain CMRR ≥ 80 dB CMRR ≥ 78 dB LMP7715, VO = 0.3 to 4.7V RL = 2 kΩ to V+/2 LMP7716, VO = 0.3 to 4.7V RL = 2 kΩ to V+/2 LMP7715, VO = 0.3 to 4.7V RL = 10 kΩ to V+/2 LMP7716, VO = 0.3 to 4.7V RL = 10 kΩ to V+/2 85 82 85 80 85 −0.3 –0.3 88 82 84 80 92 88 90 86 107 90 110 95 dB Conditions Min (Note 5) Typ (Note 4) Max (Note 5) Units ± 10 –1 –1.75 0.1 0.01 100 100 98 ± 150 ± 450 ±4 50 100 25 50 µV µV/˚C pA pA dB dB 4 4 V 3 www.national.com LMP7715/LMP7716 5V Electrical Characteristics VO Output Swing High (Continued) 70 77 60 66 32 22 42 50 20 46 38 10.5 6.5 66 23 1.15 1.30 6.0 7.5 9.5 11.5 17 7.0 5.8 0.01 0.001 0.004 % 1.40 1.75 1.70 2.05 mA 70 73 75 78 60 62 mV mV from V+ RL = 2 kΩ to V+/2 RL = 10 kΩ to V+/2 Output Swing Low RL = 2 kΩ to V+/2 (LMP7715) RL = 2 kΩ to V+/2 (LMP7716) RL = 10 kΩ to V+/2 IO Output Short Circuit Current Sourcing to V− VIN = 200 mV (Note 9) Sinking to V+ VIN = −200 mV (Note 9) IS Supply Current LMP7715 LMP7716 (per channel) mA SR GBW en in THD+N Slew Rate Gain Bandwidth Product Input-Referred Voltage Noise Input-Referred Current Noise Total Harmonic Distortion + Noise AV = +1, Rising (10% to 90%) AV = +1, Falling (90% to 10%) f = 400 Hz f = 1 kHz f = 1 kHz f = 1 kHz, AV = 1, RL = 100 kΩ VO = 4 VPP f = 1 kHz, AV = 1, RL = 600Ω VO = 4 VPP V/µs MHz nV/ pA/ www.national.com 4 LMP7715/LMP7716 Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see the Electrical Characteristics Tables. Note 2: Human Body Model is 1.5 kΩ in series with 100 pF. Machine Model is 0Ω in series with 200 pF. Note 3: The maximum power dissipation is a function of TJ(MAX), θJA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(MAX) - TA)/θJA. All numbers apply for packages soldered directly onto a PC Board. Note 4: Typical values represent the most likely parametric norm at the time of characterization. Note 5: Limits are 100% production tested at 25˚C. Limits over the operating temperature range are guaranteed through correlations using the Statistical Quality Control (SQC) method. Note 6: Offset voltage average drift is determined by dividing the change in VOS at the temperature extremes by the total temperature change. Note 7: Positive current corresponds to current flowing into the device. Note 8: Guaranteed by design. Note 9: The short circuit test is a momentary open loop test. Connection Diagrams 5-Pin SOT23 8-Pin MSOP 20183601 20183602 Top View Top View Ordering Information Package 5-Pin SOT23 8-Pin MSOP Part Number LMP7715MF LMP7715MFX LMP7716MM LMP7716MMX Package Marking AV3A AX3A Transport Media 1k Units Tape and Reel 3k Units Tape and Reel 1k Units Tape and Reel 3.5k Units Tape and Reel NSC Drawing MF05A MUA08A 5 www.national.com LMP7715/LMP7716 Typical Performance Characteristics Offset Voltage Distribution Unless otherwise noted: TA = 25˚C, VS = 5V, VCM = VS/2. TCVOS Distribution (LMP7715) 20183681 20183603 Offset Voltage Distribution TCVOS Distribution (LMP7716) 20183622 20183680 Offset Voltage vs. VCM Offset Voltage vs. VCM 20183610 20183611 www.national.com 6 LMP7715/LMP7716 Typical Performance Characteristics Unless otherwise noted: TA = 25˚C, VS = 5V, VCM = VS/2. (Continued) Offset Voltage vs. VCM Offset Voltage vs. Supply Voltage 20183612 20183621 Offset Voltage vs. Temperature CMRR vs. Frequency 20183656 20183609 Input Bias Current vs. VCM Input Bias Current vs. VCM 20183623 20183624 7 www.national.com LMP7715/LMP7716 Typical Performance Characteristics Unless otherwise noted: TA = 25˚C, VS = 5V, VCM = VS/2. (Continued) Supply Current vs. Supply Voltage (LMP7715) Supply Current vs. Supply Voltage (LMP7716) 20183605 20183677 Crosstalk Rejection Ratio (LMP7716) Sourcing Current vs. Supply Voltage 20183676 20183620 Sinking Current vs. Supply Voltage Sourcing Current vs. Output Voltage 20183619 20183650 www.national.com 8 LMP7715/LMP7716 Typical Performance Characteristics Unless otherwise noted: TA = 25˚C, VS = 5V, VCM = VS/2. (Continued) Sinking Current vs. Output Voltage Output Swing High vs. Supply Voltage 20183654 20183617 Output Swing Low vs. Supply Voltage Output Swing High vs. Supply Voltage 20183615 20183616 Output Swing Low vs. Supply Voltage Output Swing High vs. Supply Voltage 20183614 20183618 9 www.national.com LMP7715/LMP7716 Typical Performance Characteristics Unless otherwise noted: TA = 25˚C, VS = 5V, VCM = VS/2. (Continued) Output Swing Low vs. Supply Voltage Open Loop Frequency Response 20183613 20183641 Open Loop Frequency Response Phase Margin vs. Capacitive Load 20183673 20183645 Phase Margin vs. Capacitive Load Overshoot and Undershoot vs. Capacitive Load 20183646 20183630 www.national.com 10 LMP7715/LMP7716 Typical Performance Characteristics Unless otherwise noted: TA = 25˚C, VS = 5V, VCM = VS/2. (Continued) Slew Rate vs. Supply Voltage Small Signal Step Response 20183638 20183629 Large Signal Step Response Small Signal Step Response 20183637 20183633 Large Signal Step Response THD+N vs. Output Voltage 20183634 20183626 11 www.national.com LMP7715/LMP7716 Typical Performance Characteristics Unless otherwise noted: TA = 25˚C, VS = 5V, VCM = VS/2. (Continued) THD+N vs. Output Voltage THD+N vs. Frequency 20183604 20183657 THD+N vs. Frequency PSRR vs. Frequency 20183655 20183628 Input Referred Voltage Noise vs. Frequency Closed Loop Frequency Response 20183639 20183636 www.national.com 12 LMP7715/LMP7716 Typical Performance Characteristics Unless otherwise noted: TA = 25˚C, VS = 5V, VCM = VS/2. (Continued) Closed Loop Output Impedance vs. Frequency 20183632 13 www.national.com LMP7715/LMP7716 Application Information LMP7715/LMP7716 The LMP7715/LMP7716 are single and dual, low noise, low offset, rail-to-rail output precision amplifiers with a wide gain bandwidth product of 17 MHz and low supply current. The wide bandwidth makes the LMP7715/LMP7716 ideal choices for wide-band amplification in portable applications. The LMP7715/LMP7716 are superior for sensor applications. The very low input referred voltage noise of only 5.8 at 1 kHz and very low input referred current noise nV/ mean more signal fidelity and higher of only 10 fA/ signal-to-noise ratio. The LMP7715/LMP7716 have a supply voltage range of 1.8V to 5.5V over a wide temperature range of 0˚C to 125˚C. This is optimal for low voltage commercial applications. For applications where the ambient temperature might be less than 0˚C, the LMP7715/LMP7716 are fully operational at supply voltages of 2.0V to 5.5V over the temperature range of −40˚C to 125˚C. The outputs of the LMP7715/LMP7716 swing within 25 mV of either rail providing maximum dynamic range in applications requiring low supply voltage. The input common mode range of the LMP7715/LMP7716 extends to 300 mV below ground. This feature enables users to utilize this device in single supply applications. The use of a very innovative feedback topology has enhanced the current drive capability of the LMP7715/ LMP7716, resulting in sourcing currents of as much as 47 mA with a supply voltage of only 1.8V. The LMP7715 is offered in the space saving SOT23 package and the LMP7716 is offered in an 8-pin MSOP. These small packages are ideal solutions for applications requiring minimum PC board footprint. CAPACITIVE LOAD The unity gain follower is the most sensitive configuration to capacitive loading. The combination of a capacitive load placed directly on the output of an amplifier along with the output impedance of the amplifier creates a phase lag which in turn reduces the phase margin of the amplifier. If phase margin is significantly reduced, the response will be either underdamped or the amplifier will oscillate. The LMP7715/LMP7716 can directly drive capacitive loads of up to 120 pF without oscillating. To drive heavier capacitive loads, an isolation resistor, RISO as shown in Figure 1, should be used. This resistor and CL form a pole and hence delay the phase lag or increase the phase margin of the overall system. The larger the value of RISO, the more stable the output voltage will be. However, larger values of RISO result in reduced output swing and reduced output current drive. INPUT CAPACITANCE CMOS input stages inherently have low input bias current and higher input referred voltage noise. The LMP7715/ LMP7716 enhance this performance by having the low input bias current of only 50 fA, as well as, a very low input referred voltage noise of 5.8 nV/ . In order to achieve this a larger input stage has been used. This larger input stage increases the input capacitance of the LMP7715/ LMP7716. Figure 2 shows typical input common mode capacitance of the LMP7715/LMP7716. 20183675 FIGURE 2. Input Common Mode Capacitance This input capacitance will interact with other impedances, such as gain and feedback resistors which are seen on the inputs of the amplifier, to form a pole. This pole will have little or no effect on the output of the amplifier at low frequencies and under DC conditions, but will play a bigger role as the frequency increases. At higher frequencies, the presence of this pole will decrease phase margin and also cause gain peaking. In order to compensate for the input capacitance, care must be taken in choosing feedback resistors. In addition to being selective in picking values for the feedback resistor, a capacitor can be added to the feedback path to increase stability. The DC gain of the circuit shown in Figure 3 is simply −R2/R1. 20183661 20183664 FIGURE 1. Isolating Capacitive Load www.national.com 14 FIGURE 3. Compensating for Input Capacitance LMP7715/LMP7716 Application Information (Continued) For the time being, ignore CF. The AC gain of the circuit in Figure 3 can be calculated as follows: (1) This equation is rearranged to find the location of the two poles: 20183660 (2) As shown in Equation (2), as the values of R1 and R2 are increased, the magnitude of the poles are reduced, which in turn decreases the bandwidth of the amplifier. Figure 4 shows the frequency response with different value resistors for R1 and R2. Whenever possible, it is best to chose smaller feedback resistors. FIGURE 5. Closed Loop Frequency Response TRANSIMPEDANCE AMPLIFIER In many applications the signal of interest is a very small amount of current that needs to be detected. Current that is transmitted through a photodiode is a good example. Barcode scanners, light meters, fiber optic receivers, and industrial sensors are some typical applications utilizing photodiodes for current detection. This current needs to be amplified before it can be further processed. This amplification is performed using a current-to-voltage converter configuration or transimpedance amplifier. The signal of interest is fed to the inverting input of an op amp with a feedback resistor in the current path. The voltage at the output of this amplifier will be equal to the negative of the input current times the value of the feedback resistor. Figure 6 shows a transimpedance amplifier configuration. CD represents the photodiode parasitic capacitance and CCM denotes the common-mode capacitance of the amplifier. The presence of all of these capacitances at higher frequencies might lead to less stable topologies at higher frequencies. Care must be taken when designing a transimpedance amplifier to prevent the circuit from oscillating. With a wide gain bandwidth product, low input bias current and low input voltage and current noise, the LMP7715/ LMP7716 are ideal for wideband transimpedance applications. 20183659 FIGURE 4. Closed Loop Frequency Response As mentioned before, adding a capacitor to the feedback path will decrease the peaking. This is because CF will form yet another pole in the system and will prevent pairs of poles, or complex conjugates from forming. It is the presence of pairs of poles that cause the peaking of gain. Figure 5 shows the frequency response of the schematic presented in Figure 3 with different values of CF. As can be seen, using a small value capacitor significantly reduces or eliminates the peaking. 15 www.national.com LMP7715/LMP7716 Application Information (Continued) Thermopiles generate voltage in response to receiving radiation. These voltages are often only a few microvolts. As a result, the operational amplifier used for this application needs to have low offset voltage, low input voltage noise, and low input bias current. Figure 8 shows a thermopile application where the sensor detects radiation from a distance and generates a voltage that is proportional to the intensity of the radiation. The two resistors, RA and RB, are selected to provide high gain to amplify this signal, while CF removes the high frequency noise. 20183669 FIGURE 6. Transimpedance Amplifier 20183627 A feedback capacitance CF is usually added in parallel with RF to maintain circuit stability and to control the frequency response. To achieve a maximally flat, 2nd order response, RF and CF should be chosen by using Equation (3) FIGURE 8. Thermopile Sensor Interface PRECISION RECTIFIER Rectifiers are electrical circuits used for converting AC signals to DC signals. Figure 9 shows a full-wave precision rectifier. Each operational amplifier used in this circuit has a diode on its output. This means for the diodes to conduct, the output of the amplifier needs to be positive with respect to ground. If VIN is in its positive half cycle then only the output of the bottom amplifier will be positive. As a result, the diode on the output of the bottom amplifier will conduct and the signal will show at the output of the circuit. If VIN is in its negative half cycle then the output of the top amplifier will be positive, resulting in the diode on the output of the top amplifier conducting and delivering the signal from the amplifier’s output to the circuit’s output. For R2/ R1 ≥ 2, the resistor values can be found by using the equation shown in Figure 9. If R2/ R1 = 1, then R3 should be left open, no resistor needed, and R4 should simply be shorted. (3) Calculating CF from Equation (3) can sometimes result in capacitor values which are less than 2 pF. This is especially the case for high speed applications. In these instances, it is often more practical to use the circuit shown in Figure 7 in order to allow more sensible choices for CF. The new feedback capacitor, CF', is (1+ RB/RA) CF. This relationship holds as long as RA