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). n Single or Dual Supplies n Low supply voltage 1.8V to 5.0V n Ultra low supply current 11µA n Low input bias current 14nA n Low input offset current 200pA n Low input offset voltage +/−0.3mV n Response time 670ns (20mV overdrive) n Input common mode voltage 0.1V beyond rails Typical Circuit Connection Diagram Applications n n n n Mobile communications Laptops and PDA’s Battery powered electronics General purpose low voltage applications DS200057-1 Top View DS200057-2 FIGURE 1. Threshold Detector © 2001 National Semiconductor Corporation DS200057 www.national.com LMV7251/LMV7255 1.8V Low Voltage Comparator with Rail-to-Rail Input January 2001 LMV7251/LMV7255 Absolute Maximum Ratings (Note 1) Wave Soldering (10 sec.) Storage Temperature Range If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. ESD Tolerance Supply Voltage V+ +/−Supply Voltage V+ +0.1V, V− −0.1V −40˚C to +85˚C Package Thermal Resisance (Note 3) Soldering Information Infrared or Convection (20 sec.) 1.8V to 5.0V Junction Temperature Range (Note 3) 5.5V Voltage at Input/Output pins +150˚C Operating Ratings (Note 1) 1KV (Note 2) Supply Voltage (V+ - V−) −65˚C to +150˚C Junction Temperature (Note 4) 200V (Note 6) VIN Differential 260˚C SOT23-5 325˚C/W SC-70 265˚C/W 235˚C 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 Condition VCM = 0.9V (Note 7) Typ (Note 4) Limits (Note 5) Units 0.3 6 8 mV max 10 uV/C nA IB Input Bias Current 14 IOS Input Offset Current 200 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) pA µA max mA min ILEAKAGE Output Leakage Current VO = 1.8V (LMV7255 only) 300 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 pA 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 1.8V AC Electrical Characteristics 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 Parameter Propagation Delay (High to Low) www.national.com Condition Typ (Note 5) Limits (Note 6) Units Input Overdrive = 20mV Load = 50pF//5kΩ 720 ns Input Overdrive = 50mV Load = 50pF//5kΩ 380 ns 2 (Continued) 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 tPLH Parameter Propagation Delay (Low to High) Condition Typ (Note 5) Limits (Note 6) Units 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 VOS Input Offset Voltage TC VOS Input Offset Average Drift Conditions VCM = 1.35V (Note 7) Typ (Note 5) Limits (Note 6) Units 0.03 6 8 mV max 10 µV/C nA IB Input Bias Current 15 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 pA µA max mA ILEAKAGE Output Leakage Current VO = 2.7V, (LMV7255 only) 320 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 pA 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 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 3 www.national.com LMV7251/LMV7255 1.8V AC Electrical Characteristics LMV7251/LMV7255 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 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 16 nA IOS 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 ILEAKAGE Output Leakage Current VO = 5V, (LMV7255 only) 375 VOH Output Voltage High IO = 4mA 4.9 4.82 V min VOL Output Voltage Low IO = −4mA 90 180 mV max VCM = 2.5V (Note 7) µA max mA min pA 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 (TA = 25˚C, Unless otherwise specified). Short Circuit Current vs. Supply Voltage Supply Current vs. Supply Voltage DS200057-4 DS200057-3 Output Voltage vs. Supply Voltage LMV7251/LMV7255 Typical Performance Characteristics Output Voltage vs. Supply Voltage DS200057-5 Output Voltage vs. Output Current @1.8V Supply Voltage DS200057-6 Output Voltage vs. Output Current @1.8V Supply Voltage DS200057-7 DS200057-8 5 www.national.com LMV7251/LMV7255 Typical Performance Characteristics Output Voltage vs. Output Current @2.7V Supply Voltage (TA = 25˚C, Unless otherwise specified). (Continued) Output Voltage vs. Output Current @2.7V Supply Voltage DS200057-9 DS200057-10 Response Time for Various Input Overdrives - tPLH Response Time for Various Input Overdrives - tPHL DS200057-11 Response Time for Various Input Overdrives - tPLH DS200057-12 Response Time for Various Input Overdrives - tPHL DS200057-13 www.national.com DS200057-14 6 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 (VO) is low (VOL). However, if VIN is greater than VREF, the output voltage (VO) is high (VOH). 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 LMV7251 The Hysteresis is the difference between VIN1 and VIN2. ∆VIN = VIN1- VIN2 = ((VREF (R1 + R2)) / R2) - ((VREF (R1 + R2) - VCC R1) / R2) = VCC R1/ R2. DS200057-15 LMV7255 DS200057-18 DS200057-16 Input/Output DS200057-19 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) DS200057-17 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). Hysteresis is the voltage difference between the two switching thresholds. When both inputs are nearly equal, 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)) The hysteresis is defined as ∆VIN = VT1 - VT2 = ((VCC R2) / ((R1 R3) / (R1+ R3)) + R2) – (VCC ((R2 R3) / (R2 + R3)) / ((R1 + ((R2 R3) / (R2 + R3))) 7 www.national.com LMV7251/LMV7255 hysteresis causes one input to effectively move quickly pass the other. Thus, effectively moving the input out of region that oscillation may occur. Application Info LMV7251/LMV7255 Application Info 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. (Continued) DS200057-20 DS200057-21 FIGURE 4. Inverting Configured Comparator — LMV7255 Input Stage The LMV7251 and LMV7255 have rail-to-rail input stages. The input common mode voltage range is from −100mV to (VCC + 100mV). 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. www.national.com 8 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 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 5-Pin SC-70 9 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 www.national.com 10 LMV7251/LMV7255 1.8V Low Voltage Comparator with Rail-to-Rail Input Physical Dimensions inches (millimeters) unless otherwise noted 5-Pin SOT23-5 NS Package Number MF05A LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. National Semiconductor Corporation Americas Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: [email protected] www.national.com National Semiconductor Europe Fax: +49 (0) 180-530 85 86 Email: [email protected] Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. 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