LM397

LM397 Single General Purpose Voltage Comparator August 2006 LM397 Single General Purpose Voltage Comparator General Description The LM397 is a single voltage comparator with an input common mode that includes ground. The LM397 is designed to operate from a single 5V to 30V power supply or a split power supply. Its low supply current is virtually independent of the magnitude of the supply voltage. The LM397 features an open collector output stage. This allows the connection of an external resistor at the output. The output can directly interface with TTL, CMOS and other logic levels, by tying the resistor to different voltage levels (level translator). The LM397 is available in space saving 5-Pin SOT23 package and pin compatible to TI’s TL331, single differential comparator. Features (TA = 25˚C. Typical values unless otherwise specified). n 5-Pin SOT23 package n Industrial operating range −40˚C to +85˚C n Single or dual power supplies n Wide supply voltage range 5V to 30V n Low supply current 300µA n Low input bias current 7nA ± 1nA n Low input offset current ± 2mV n Low input offset voltage n Response time 440ns (50mV overdrive) n Input common mode voltage 0 to VS - 1.5V Applications n n n n A/D converters Pulse, square wave generators Peak detector Industrial applications Connection Diagram 5-Pin SOT23 Typical Circuit 20022108 Top View 20022109 FIGURE 1. Inverting Comparator with Hysteresis Ordering Information Package 5-Pin SOT-23 Part Number LM397MF LM397MFX Package Marking C397 Transport Media 1k Units Tape and Reel 3k Units Tape and Reel NSC Drawing MF05A © 2006 National Semiconductor Corporation DS200221 www.national.com LM397 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 Voltages Voltage at Input Pins Storage Temperature Range 2KV 200V 30V 30V or ± 15V −0.3V to 30V −65˚C to +150˚C Junction Temperature (Note 3) Soldering Information Infrared or Convection (20 sec.) Wave Soldering (10 sec.) +150˚C 235˚C 260˚C Operating Ratings (Note 1) Supply Voltage, VS Temperature Range (Note 3) Package Thermal Resistance (Note 3) 5-Pin SOT23 168˚C/W 5V to 30V −40˚C to +85˚C Electrical Characteristics Unless otherwise specified, all limits are guaranteed for TA = 25˚C, VS = 5V, V− = 0V, VCM = V+/2 = VO. Boldface limits apply at the temperature extremes. Symbol VOS IOS IB IS IO ILEAKAGE VOL VCM AV tPHL Parameter Input Offset Voltage Input Offset Current Input Bias Current Supply Current Output Sink Current Output Leakage Current Output Voltage Low Conditions VS = 5V to 30V, VO = 1.4V, VCM = 0V VO = 1.4V, VCM = 0V VO = 1.4V, VCM = 0V RL = Open, VS = 5V RL = Open, VS = 30V VIN+ = 1V,VIN− = 0V, VO = 1.5V VIN+ = 1V,VIN− = 0V, VO = 5V VIN+ = 1V,VIN− = 0V, VO = 30V IO = −4mA, VIN+ = 0V,VIN− = 1V 0 0 120 900 250 940 440 ns 6 Min (Note 5) Typ (Note 4) 2 1.6 10 0.25 0.30 13 0.1 1 180 400 700 VS - 1.5V VS - 2V Max (Note 5) 7 10 50 250 250 400 0.7 2 Units mV nA nA mA mA nA µA mV Common-Mode Input Voltage VS = 5V to 30V (Note 6) Range Voltage Gain Propagation Delay (High to Low) VS = 15V, VO = 1.4V to 11.4V, RL > = 15kΩ connected to VS Input Overdrive = 5mV RL = 5.1kΩ connected to 5V, CL = 15pF Input Overdrive = 50mV RL = 5.1kΩ connected to 5V, CL = 15pF V V/mV tPLH Propagation Delay (Low to High) Input Overdrive = 5mV RL = 5.1kΩ connected to 5V, CL = 15pF Input Overdrive = 50mV RL = 5.1kΩ connected to 5V, CL = 15pF µs ns 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, applicable std. MIL-STD-883, Method 3015.7. Machine Model, applicable std. JESD22-A115-A (ESD MM std. of JEDEC) Field-Induced Charge-Device Model, applicable std. JESD22-C101-C (ESD FICDM std. of JEDEC). 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 as determined at the time of characterization. Actual typical values may vary over time and will also depend on the application and configuration. The typical values are not tested and are not guaranteed on shipped production material. Note 5: All limits are guaranteed by testing or statistical analysis. Note 6: The input common-mode voltage of either input should not be permitted to go below the negative rail by more than 0.3V. The upper end of the common-mode voltage range is VS - 1.5V at 25˚C. www.national.com 2 LM397 Typical Performance Characteristics Supply Current vs. Supply Voltage TA = 25˚C. Unless otherwise specified. Input Bias Current vs. Supply Current 20022103 20022101 Output Saturation Voltage vs. Output Sink Current Input Offset Voltage vs. Supply Voltage 20022104 20022102 Response Time for Various Input Overdrives – tPHL Response Time for Various Input Overdrives – tPLH 20022105 20022106 3 www.national.com LM397 Application Notes 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). Refer to Figure 2. 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 = ((VS 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 = VS ((R2 R3) / (R2 + R3)) / (R1 + ((R2 R3) / (R2 + R3))) The hysteresis is defined as ∆VIN = VT1 – VT2 20022110 20022112 20022111 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, hysteresis causes one input to effectively move quickly pass the other. Thus, effectively moving the input out of region that oscillation may occur. For an inverting configured comparator, hysteresis can be added with a three resistor network and positive feedback. 20022113 FIGURE 3. Inverting Configured Comparator – LM397 www.national.com 4 LM397 Application Notes Input Stage (Continued) The LM397 has a bipolar input stage. The input common mode voltage range is from 0 to (VS – 1.5V). Output Stage The LM397 has an open collector grounded-emitter NPN output transistor for the 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. Because it is an open collector output stage, several comparator outputs can be connected together to create an OR’ing function output. With an open collector, the output can be used as a simple SPST switch to ground.The amount of current which the output can sink is approximately 10mA. When the maximum current limit is reached, the output transistor will saturate and the output will rise rapidly (Figure 4). 20022107 FIGURE 4. Output Saturation Voltage vs. Output Sink Current 5 www.national.com LM397 SOT23-5 Tape and Reel Specification Tape Format Tape Section Leader (Start End) Carrier Trailer (Hub End) # Cavities 0 (min) 75 (min) 3000 1000 125 (min) 0 (min) Cavity Status Empty Empty Filled Filled Empty Empty Cover Tape Status Sealed Sealed Sealed Sealed Sealed Sealed TAPE DIMENSIONS 20022115 8mm Tape Size 0.130 (3.3) DIM A 0.124 (3.15) DIM Ao 0.130 (3.3) DIM B 0.126 (3.2) DIM Bo 0.138 ± 0.002 (3.5 ± 0.05) DIM F 0.055 ± 0.004 (1.4 ± 0.11) DIM Ko 0.157 (4) DIM P1 0.315 ± 0.012 (8 ± 0.3) DIM W www.national.com 6 LM397 SOT23-5 Tape and Reel Specification REEL DIMENSIONS (Continued) 20022116 8mm Tape Size 7.00 330.00 A 0.059 1.50 B 0.512 13.00 C 0.795 20.20 D 2.165 55.00 N 0.331 + 0.059/−0.000 8.40 + 1.50/−0.00 W1 0.567 14.40 W2 W1 + 0.078/−0.039 W1 + 2.00/−1.00 W3 7 www.national.com LM397 Single General Purpose Voltage Comparator Physical Dimensions inches (millimeters) unless otherwise noted 5-Pin SOT23 NS Package Number MF05A National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. 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