LMV7251M5

October 13, 2011 LMV7251/LMV7255 1.8V Low Voltage Comparator with Rail-to-Rail Input General Description Features The LMV7251/LMV7255 are rail-to-rail input low voltage comparators, which can operate at supply voltage range of 1.8V to 5.0V. The LMV7251/LMV7255 are available in space saving SC-70 or SOT23-5 packages. These comparators are ideal for low voltage and space critical designs. The LMV7251 features a push-pull output stage. This feature allows operation with minimum power consumption when driving a load. The LMV7255 features an open drain output. This allows the connection of an external resistor at the output. The output of the comparator can be used as a level shifter. The IC's are built with National Semiconductor's advance Submicron Silicon-Gate BiCMOS process. The LMV7251/ LMV7255 have bipolar inputs for improved noise performance and CMOS outputs for better rail-to-rail output performance. (VS = 1.8V, TA = 25°C, Typical values unless specified). ■ Single or Dual Supplies 1.8V to 5.0V ■ Low supply voltage 11µA ■ Ultra low supply current 14nA ■ Low input bias current 200pA ■ Low input offset current +/−0.3mV ■ Low input offset voltage 670ns (20mV overdrive) ■ Response time 0.1V beyond rails ■ Input common mode voltage Typical Circuit Connection Diagram Applications ■ ■ ■ ■ Mobile communications Laptops and PDA's Battery powered electronics General purpose low voltage applications 20005701 Top View 20005702 FIGURE 1. Threshold Detector © 2011 National Semiconductor Corporation 200057 200057 Version 5 Revision 2 www.national.com Print Date/Time: 2011/10/13 15:13:37 LMV7251/LMV7255 1.8V Low Voltage Comparator with Rail-to-Rail Input OBSOLETE LMV7251/LMV7255 Wave Soldering (10 sec.) Storage Temperature Range Junction Temperature (Note 4) 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 Operating Ratings 1KV (Note 2) 200V (Note 6) +/−Supply Voltage 5.5V V+ +0.1V, V− −0.1V VIN Differential Supply Voltage (V+ - V−) Voltage at Input/Output pins Soldering Information Infrared or Convection (20 sec.) 260°C −65°C to +150°C +150°C (Note 1) V+ Supply Voltage Junction Temperature Range (Note 3) Package Thermal Resisance (Note 3) SOT23-5 SC-70 235°C 1.8V to 5.0V −40°C to +85°C 325°C/W 265°C/W 1.8V Electrical Characteristics Unless otherwise specified, all limits guaranteed for TJ = 25°C, V+ = 1.8V, V− = 0V. Boldface limits apply at the temperature extremes. Symbol Parameter VOS Input Offset Voltage TC VOS Input Offset Average Drift IB IOS Condition VCM = 0.9V (Note 7) Typ (Note 4) Limits (Note 5) Units 0.3 6 8 mV max 10 uV/C Input Bias Current 14 nA Input Offset Current 200 pA IS Supply Current 11 15 17 ISC Output Short Circuit Current 8 4 Sinking, VO = 0.9V 11.6 5 Sourcing, VO = 0.9V (LMV7251 only) µA max mA min ILEAKAGE Output Leakage Current VO = 1.8V (LMV7255 only) 300 pA VOH Output Voltage High IO = 1.5mA (LMV7251 only) 1.72 1.675 V min VOL Output Voltage Low IO = −1.5mA 65 125 mV max VCM Input Common Voltage Range CMRR > 45 dB 1.9 V max −0.1 V min CMRR Common Mode Rejection Ratio 0 < VCM < 1.8V 72 47 dB min PSRR Power Supply Rejection Ratio V+ = 1.8V to 5V 79 55 dB min www.national.com 2 200057 Version 5 Revision 2 Print Date/Time: 2011/10/13 15:13:37 Unless otherwise specified, all limits guaranteed for TJ = 25°C, V+ = 1.8V, V− = 0V, VCM = 0.5V, VO = V+/2. Boldface limits apply at the temperature extremes. Symbol tPHL tPLH Parameter Propagation Delay (High to Low) Propagation Delay (Low to High) Condition Typ (Note 5) Limits (Note 6) Units Input Overdrive = 20mV Load = 50pF//5kΩ 720 ns Input Overdrive = 50mV Load = 50pF//5kΩ 380 ns Input Overdrive = 20mV Load = 50pF//5kΩ 670 ns Input Overdrive = 50mV Load = 50pF//5kΩ 400 ns 2.7V Electrical Characteristics Unless otherwise specified, all limits guaranteed for TJ = 25°C, V+ = 2.7V, V− = 0V. Boldface limits apply at the temperature extremes. Symbol Parameter Conditions Typ (Note 5) Limits (Note 6) Units 0.03 6 8 mV max VOS Input Offset Voltage TC VOS Input Offset Average Drift 10 µV/C IB Input Bias Current 15 nA IOS Input offset Current 210 IS Supply Current 11 18 22 ISC Output Short Circuit Current Sourcing, VO = 1.35V (LMV7251 only) 28 15 Sinking, VO = 1.35V 28 15 VCM = 1.35V (Note 7) pA µA max mA ILEAKAGE Output Leakage Current VO = 2.7V, (LMV7255 only) 320 pA VOH Output Voltage High IO = 2mA (LMV7251 only) 2.63 2.575 V min VOL Output Voltage Low IO = −2mA 61 125 mV max VCM Input Common Voltage Range CMRR > 45dB 2.8 V max −0.1 V min CMRR Common Mode Rejection Ratio 0 < VCM < 2.7V 75 46 dB min PSRR Power Supply Rejection Ratio V+ = 1.8V to 5V 79 55 dB min 3 200057 Version 5 Revision 2 Print Date/Time: 2011/10/13 15:13:37 www.national.com LMV7251/LMV7255 1.8V AC Electrical Characteristics LMV7251/LMV7255 2.7V AC Electrical Characteristics Unless otherwise specified, all limits guaranteed for TJ = 25°C, V+ = 2.7V, V− = 0V.Boldface limits apply at the temperature extremes. Symbol tPHL tPLH Parameter Propagation Delay (High to Low) Propagation Delay (Low to High) Condition Typ (Note 5) Limits (Note 6) Units Input Overdrive = 20mV Load = 50pF//5kΩ 830 ns Input Overdrive = 50mV Load = 50pF//5kΩ 430 ns Input Overdrive = 20mV Load = 50pF//5kΩ 730 ns Input Overdrive = 50mV Load = 50pF//5kΩ 410 ns 5V Electrical Characteristics Unless otherwise specified, all limits guaranteed for TJ = 25°C, V+ = 5V, V− = 0V. Boldface limits apply at the temperature extremes. Symbol Parameter VOS Input Offset Voltage TC VOS Input Offset Average Drift IB IOS Conditions VCM = 2.5V (Note 7) Typ (Note 5) Limits (Note 6) Units 0.03 6 8 mV max 10 µV/C Input Bias Current 16 nA Input Offset Current 220 pA IS Supply Current 12 20 25 ISC Output Short Circuit Current Sourcing, VO = 2.5V (LMV7251 only) 82 50 Sinking, VO = 2.5V 78 50 µA max mA min ILEAKAGE Output Leakage Current VO = 5V, (LMV7255 only) 375 pA VOH Output Voltage High IO = 4mA 4.9 4.82 V min VOL Output Voltage Low IO = −4mA 90 180 mV max 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. Note 2: Human body model, 1.5kΩ in series with 100pF. Note 3: The maximum power dissipation is a function of TJ(max), θJA, and TA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(max) - TA)/θJA. All numbers apply for packages soldered directly into a PC board. Note 4: Typical values represent the most likely parametric norm. Note 5: All limits are guaranteed by testing or statistical analysis. Note 6: Machine Model, 0Ω in series with 200pF. Note 7: Offset Voltage average drift determined by dividing the change in VOS at temperature extremes into the total temperature change. www.national.com 4 200057 Version 5 Revision 2 Print Date/Time: 2011/10/13 15:13:37 LMV7251/LMV7255 Typical Performance Characteristics (TA = 25°C, Unless otherwise specified). Short Circuit Current vs. Supply Voltage Supply Current vs. Supply Voltage 20005704 20005703 Output Voltage vs. Supply Voltage Output Voltage vs. Supply Voltage 20005705 20005706 Output Voltage vs. Output Current @1.8V Supply Voltage Output Voltage vs. Output Current @1.8V Supply Voltage 20005707 20005708 5 200057 Version 5 Revision 2 Print Date/Time: 2011/10/13 15:13:37 www.national.com LMV7251/LMV7255 Output Voltage vs. Output Current @2.7V Supply Voltage Output Voltage vs. Output Current @2.7V Supply Voltage 20005709 20005710 Response Time for Various Input Overdrives - tPLH Response Time for Various Input Overdrives - tPHL 20005711 20005712 Response Time for Various Input Overdrives - tPLH Response Time for Various Input Overdrives - tPHL 20005713 www.national.com 20005714 6 200057 Version 5 Revision 2 Print Date/Time: 2011/10/13 15:13:37 BASIC COMPARATORS A comparator is quite often used to convert an analog signal to a digital signal. The comparator compares an input voltage (VIN) at the non-inverting pin to the reference voltage (VREF) at the inverting pin. If VIN is less than VREF the output (V O) is low (VOL). However, if VIN is greater than VREF, the output voltage (VO) is high (VOH). LMV7251 ΔVIN = VIN1- VIN2 = ((VREF (R1 + R2)) / R2) - ((VREF (R1 + R2) - VCC R1) / R2) = VCC R1/ R2. 20005715 LMV7255 20005718 20005716 Input/Output 20005719 FIGURE 3. Non-Inverting Comparator Configuration — LMV7251 For an inverting configured comparator, hysteresis can be added with a three resistor network and positive feedback. When input voltage (VIN) at the inverting node is less than non-inverting node (VT), the output is high. The equivalent circuit for the three resistor network is R1 in parallel with R3 and in series with R2. The lower threshold voltage VT1 is calculated by: VT1 = ((VCC R2) / ((R1 R3) / (R1+ R3)) + R2) When VIN is greater than VT, the output voltage is low. The equivalent circuit for the three resistor network is R2 in parallel with R3 and in series with R1. The upper threshold voltage VT2 is calculated by: VT2 = VCC ((R2 R3) / (R2 + R3)) / ((R1 + ((R2 R3) / (R2 + R3)) 20005717 FIGURE 2. Basic Comparator HYSTERESIS The basic comparator configuration may oscillate or produce a noisy output if the applied differential input is near the comparator's input offset voltage. This tends to occur when the voltage on the input is equal or very close to the other input voltage. Adding hysteresis can prevent this problem. Hysteresis creates two switching thresholds (one for the rising input voltage and the other for the falling input voltage). Hys- 7 200057 Version 5 Revision 2 Print Date/Time: 2011/10/13 15:13:37 www.national.com LMV7251/LMV7255 teresis is the voltage difference between the two switching thresholds. When both inputs are nearly equal, hysteresis causes one input to effectively move quickly pass the other. Thus, effectively moving the input out of region that oscillation may occur. Hysteresis can easily be added to a comparator in a non-inverting configuration with two resistors and positive feedback Figure 3. The output will switch from low to high when VIN rises up to VIN1, where VIN1 is calculated by VIN1 = (VREF (R1 + R2))/ R2 The output will switch from high to low when VIN falls to VIN2, where VIN2 is calculated by VIN2 = (VREF (R1 + R2) - VCC R1) / R2 The Hysteresis is the difference between VIN1 and VIN2. Application Info LMV7251/LMV7255 The hysteresis is defined as INPUT STAGE The LMV7251 and LMV7255 have rail-to-rail input stages. The input common mode voltage range is from −100mV to (VCC + 100mV). ΔVIN = VT1 - VT2 = ((VCC R2) / ((R1 R3) / (R1+ R3)) + R2) – (VCC ((R2 R3) / (R2 + R3)) / ((R1 + ((R2 R3) / (R2 + R3))) OUTPUT STAGE The LMV7251 has a push-pull CMOS output stage. Large push-pull output drivers allows rail-to-rail output swings with load currents in the miliampere range. The LMV7255 has a open drain CMOS output stage. This requires an external pull-up resistor connected between the positive supply voltage and the output. The external pull-up resistor should be high enough resistance so to avoid excessive power dissipation. In addition, the pull-up resistor should be low enough resistance to enable the comparator to switch with the load circuitry connected. POWER SUPPLY CONSIDERATIONS The LMV7251/LMV7255 are well suited for many batterypowered applications. The LMV7251/LMV7255 can operate from single power supply of +1.8V to +5V. The device typically consumes only 11µA with a 2.7V supply. With a high power supply rejection ratio (PSRR) of 79 dB (typical), the comparator is well suited for operating under conditions of a decaying battery voltage. Power supply decoupling is critical and improves stability. Place decoupling capacitors 0.1µF as close as possible to the V+ pin. For split supply applications, place decoupling capacitors 0.1µF on both the V+ and V− pins. The decoupling capacitors will help keep the comparator from oscillating under various load conditions. 20005720 20005721 FIGURE 4. Inverting Configured Comparator — LMV7255 www.national.com 8 200057 Version 5 Revision 2 Print Date/Time: 2011/10/13 15:13:37 Package Ordering Info Pkg Marking Supplied As NSC Drawing 5-Pin SOT23-5 LMV7251M5 C16A 1k Units Tape and Reel MF05A LMV7251M5X C16A 3k units Tape and Reel LMV7255M5 C18A 1k Units Tape and Reel LMV7255M5X C18A 3k units Tape and Reel 5-Pin SC-70 LMV7251M7 C17 1k Units Tape and Reel LMV7251M7X C17 3k units Tape and Reel LMV7255M7 C19 1k Units Tape and Reel LMV7255M7X C19 3k units Tape and Reel 9 200057 Version 5 Revision 2 Print Date/Time: 2011/10/13 15:13:37 MAA05A www.national.com LMV7251/LMV7255 Ordering Information LMV7251/LMV7255 Physical Dimensions inches (millimeters) unless otherwise noted 5-Pin SC70-5 NS Package Number MAA05A 5-Pin SOT23-5 NS Package Number MF05A www.national.com 10 200057 Version 5 Revision 2 Print Date/Time: 2011/10/13 15:13:37 LMV7251/LMV7255 Notes 11 200057 Version 5 Revision 2 Print Date/Time: 2011/10/13 15:13:37 www.national.com LMV7251/LMV7255 1.8V Low Voltage Comparator with Rail-to-Rail Input Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Design Support Amplifiers www.national.com/amplifiers WEBENCH® Tools www.national.com/webench Audio www.national.com/audio App Notes www.national.com/appnotes Clock and Timing www.national.com/timing Reference Designs www.national.com/refdesigns Data Converters www.national.com/adc Samples www.national.com/samples Interface www.national.com/interface Eval Boards www.national.com/evalboards LVDS www.national.com/lvds Packaging www.national.com/packaging Power Management www.national.com/power Green Compliance www.national.com/quality/green Switching Regulators www.national.com/switchers Distributors www.national.com/contacts LDOs www.national.com/ldo Quality and Reliability www.national.com/quality LED Lighting www.national.com/led Feedback/Support www.national.com/feedback Voltage References www.national.com/vref Design Made Easy www.national.com/easy www.national.com/powerwise Applications & Markets www.national.com/solutions Mil/Aero www.national.com/milaero PowerWise® Solutions Serial Digital Interface (SDI) www.national.com/sdi Temperature Sensors www.national.com/tempsensors SolarMagic™ www.national.com/solarmagic PLL/VCO www.national.com/wireless www.national.com/training PowerWise® Design University THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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