LMV7219

LMV7219 7 nsec, 2.7V to 5V Comparator with Rail-to-Rail Output November 2004 LMV7219 7 nsec, 2.7V to 5V Comparator with Rail-to-Rail Output General Description The LMV7219 is a low-power, high-speed comparator with internal hysteresis. The LMV7219 operating voltage ranges from 2.7V to 5V with push/pull rail-to-rail output. This device achieves a 7ns propagation delay while consuming only 1.1mA of supply current at 5V. The LMV7219 inputs have a common mode voltage range that extends 200mV below ground, allowing ground sensing. The internal hysteresis ensures clean output transitions even with slow-moving inputs signals. The LMV7219 is available in the SC70-5 and SOT23-5 packages, which are ideal for systems where small size and low power are critical. Features (VS = 5V, TA = 25˚C, Typical values unless specified) n Propagation delay 7ns n Low supply current 1.1mA n Input common mode voltage range extends 200mv below ground n Ideal for 2.7V and 5V single supply applications n Internal hysteresis ensures clean switching n Fast rise and fall time 1.3ns n Available in space-saving packages: 5-pin SC70-5 and SOT23-5 Applications n n n n n n n Portable and battery-powered systems Scanners Set top boxes High speed differential line receiver Window comparators Zero-crossing detectors High-speed sampling circuits Typical Application 10105401 © 2004 National Semiconductor Corporation DS101054 www.national.com LMV7219 Connection Diagram SC70-5/SOT23-5 10105402 Top View Ordering Information Package 5-pin SC70-5 5-pin SOT23-5 Part Number LMV7219M7 LMV7219M7X LMV7219M5 LMV7219M5X Marking C15 C15 C14A C14A Supplied as 1k Units Tape and Reel 3k Units Tape and Reel 1k Units Tape and Reel 3k Units Tape and Reel NSC Drawing MAA05A MF05A Simplified Schematic 10105403 www.national.com 2 LMV7219 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) Machine Body Human Model Body Differential Input Voltage Output Short Circuit Duration Supply Voltage (V+ - V−) Soldering Information Infrared or Convection (20 sec) Wave Soldering (10 sec) 235˚C 260˚C (lead temp) 150V 2000V Voltage at Input/Output pins Current at Input Pin (Note 9) (V+) + 0.4V (V−) − 0.4V ± 10mA Operating Ratings Supply voltages (V+ - V−) Operating Temperature Range (Note 4) Storage Temperature Range Package Thermal Resistance SC70-5 SOT23-5 478˚C/W 265˚C/W 2.7V to 5V −40˚C to +85˚C −65˚C to +150˚C ± Supply Voltage (Note 3) 5.5V 2.7V Electrical Characteristics Unless otherwise specified, all limits guaranteed for TJ = 25˚C, VCM = V+/2, V+ = 2.7V, V− = 0V, CL = 10 pF and RL > 1 MΩ to V−. Boldface limits apply at the temperature extremes. Symbol VOS IB IOS CMRR PSRR VCM Parameter Input Offset Voltage Input Bias Current Input Offset Current Common Mode Rejection Ratio Power Supply Rejection Ratio Input Common-Voltage Range 0V < VCM < 1.50V V+ = 2.7V to 5V CMRR > 50 dB Conditions Typ (Note 5) 1 450 50 85 85 VCC −1 −0.2 VO Output Swing High IL = 4 mA, VID = 500 mV IL = 0.4 mA, VID = 500 mV Output Swing Low IL = −4 mA, VID = −500 mV IL = −0.4 mA, VID = −500 mV ISC Output Short Circuit Current Sourcing, VO = 0V (Note 3) Sinking, VO = 2.7V (Note 3) IS VHYST VTRIP+ VTRIP− Supply Current Input Hysteresis Voltage Input Referred Positive Trip Point Input Referred Negative Trip Point No Load (Note 10) (see Figure 1) (see Figure 1) VCC −0.22 VCC −0.02 130 15 20 20 0.9 7 3 −4 8 −8 1.6 2.2 mA Limit (Note 6) 6 8 950 2000 200 400 62 55 65 55 VCC −1.2 VCC −1.3 −0.1 0 VCC −0.3 VCC −0.4 VCC −0.05 VCC −0.15 200 300 50 150 Units mV max nA max nA max dB min dB min V min V max V min mV max mA max mV mV max mV min 3 www.national.com LMV7219 2.7V Electrical Characteristics Symbol tPD Parameter Propagation Delay (Continued) Unless otherwise specified, all limits guaranteed for TJ = 25˚C, VCM = V+/2, V+ = 2.7V, V− = 0V, CL = 10 pF and RL > 1 MΩ to V−. Boldface limits apply at the temperature extremes. Conditions Overdrive = 5 mV VCM = 0V (Note 7) Overdrive = 15 mV VCM = 0V (Note 7) Overdrive = 50 mV VCM = 0V (Note 7) Typ (Note 5) 12 11 10 1 2.5 2 20 ns ns ns ns max Limit (Note 6) Units tSKEW tr tf Propagation Delay Skew Output Rise Time Output Fall Time (Note 8) 10% to 90% 90% to 10% 5V Electrical Characteristics Unless otherwise specified, all limits guaranteed for TJ = 25˚C, VCM = V+/2, V+ = 5V, V− = 0V, CL = 10 pF and RL > 1 MΩ to V−. Boldface limits apply at the temperature extremes. Symbol VOS IB IOS CMRR PSRR VCM Parameter Input Offset Voltage Input Bias Current Input Offset Current Common Mode Rejection Ratio Power Supply Rejection Ratio Input Common-Mode Voltage Range 0V < VCM < 3.8V V+ = 2.7V to 5V CMRR > 50 dB Conditions Typ (Note 5) 1 500 50 85 85 VCC −1 −0.2 VO Output Swing High IL = 4 mA, VID = 500 mV IL = 0.4 mA, VID = 500 mV Output Swing Low IL = −4 mA, VID = −500 mV IL = −0.4 mA, VID = −500 mV ISC Output Short Circuit Current Sourcing, VO = 0V (Note 3) Sinking, VO = 5V (Note 3) IS VHYST VTrip+ VTrip− Supply Current Input Hysteresis Voltage Input Referred Positive Trip Point Input Referred Negative Trip Point No Load (Note 10) (See figure 1) (See figure 1) VCC −0.13 VCC −0.02 80 10 68 65 1.1 7.5 3.5 −4 8 −8 Limit (Note 6) 6 8 950 2000 200 400 65 55 65 55 VCC −1.2 VCC −1.3 −0.1 0 VCC −0.2 VCC −0.3 VCC −0.05 VCC −0.15 180 280 50 150 30 20 30 20 1.8 2.4 Units mV max nA max nA max dB min dB min V min V max V min mV max mA min mA max mV mV max mV min www.national.com 4 LMV7219 5V Electrical Characteristics Symbol tPD Parameter Propagation Delay (Continued) Unless otherwise specified, all limits guaranteed for TJ = 25˚C, VCM = V+/2, V+ = 5V, V− = 0V, CL = 10 pF and RL > 1 MΩ to V−. Boldface limits apply at the temperature extremes. Conditions Overdrive = 5 mV VCM = 0V (Note 7) Overdrive = 15mV VCM = 0V (Note 7) Overdrive = 50 mV VCM = 0V (Note 7) Typ (Note 5) 9 8 7 0.4 1.3 1.25 20 19 ns ns ns ns max Limit (Note 6) Units tSKEW tr tf Propagation Delay Skew Output Rise Time Output Fall Time (Note 8) 10% to 90% 90% to 10% 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, 1.5 kΩ in series with 100 pF. Machine model, 200Ω in series with 100 pF. Note 3: Applies to both single-supply and split-supply operation. Continuous short circuit operation at elevated ambient temperature can result in exceeding the maximum allowed junction temperature of 150˚C. Output currents in excess of ± 30mA over long term may adversely affect reliability. Note 4: 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 5: Typical Values represent the most likely parametric norm. Note 6: All limits are guaranteed by testing or statistical analysis. Note 7: Propagation delay measurements made with 100 mV steps. Overdrive is measure relative to VTrip. Note 8: Propagation Delay Skew is defined as absolute value of the difference between tPDLH and tPDHL. Note 9: Limiting input pin current is only necessary for input voltages that exceed absolute maximum input voltage ratings. Note 10: The LMV7219 comparator has internal hysteresis. The trip points are the input voltage needed to change the output state in each direction. The offset voltage is defined as the average of Vtrip+ and Vtrip−, while the hysteresis voltage is the difference of these two. 5 www.national.com LMV7219 Typical Performance Characteristics Supply Current vs. Supply Voltage Unless otherwise specified, VS = 5V, CL = 10 pF, TA = 25˚C VOS vs. Supply Voltage 10105404 10105405 Input Offset and Trip Voltage vs. Supply Voltage Sourcing Current vs. Output Voltage 10105406 10105408 Sourcing Current vs. Output Voltage Sinking Current vs. Output Voltage 10105409 10105410 www.national.com 6 LMV7219 Typical Performance Characteristics Unless otherwise specified, VS = 5V, CL = 10 pF, TA = 25˚C (Continued) Propagation Delay vs. Temperature (VS = 2.7V, VOD = 15 mV) Sinking Current vs. Output Voltage 10105411 10105412 Propagation Delay vs. Temperature (VS = 5V, VOD = 15 mV) Propagation Delay vs. Capacitive Load (VS = 5V, VOD = 15 mV) 10105413 10105414 Propagation Delay vs. Input Overdrive Propagation Delay (tPD−) 10105416 10105415 7 www.national.com LMV7219 Typical Performance Characteristics Unless otherwise specified, VS = 5V, CL = 10 pF, TA = 25˚C (Continued) Propagation Delay (tPD+) 10105417 Application Section LMV7219 is a single supply comparator with internal hysteresis, 7ns of propagation delay and only 1.1mA of supply current. The LMV7219 has a typical input common mode voltage range of −0.2V below the ground to 1V below Vcc. The differential input stage is a pair of PNP transistors, therefore, the input bias current flows out of the device. If either of the input signals falls below the negative common mode limit, the parasitic PN junction formed by the substrate and the base of the PNP will turn on, resulting in an increase of input bias current. If one of the inputs goes above the positive common mode limit, the output will still maintain the correct logic level as long as the other input stays within the common mode range. However, the propagation delay will increase. When both inputs are outside the common mode voltage range, current saturation occurs in the input stage, and the output becomes unpredictable. The propagation delay does not increase significantly with large differential input voltages. However, large differential voltages greater than the supply voltage should be avoided to prevent damages to the input stage. The LMV7219 has a push pull output. When the output switches, there is a direct path between VCC and ground, causing high output sinking or sourcing current during the transition. After the transition, the output current decreases and the supply current settles back to about 1.1mA at 5V, thus conserving power consumption. Most high-speed comparators oscillate when the voltage of one of the inputs is close to or equal to the voltage on the other input due to noise or undesirable feedback. The LMV7219 have 7mV of internal hysteresis to counter parasitic effects and noise. The hysteresis does not change significantly with the supply voltages and the common mode input voltages as reflected in the specification table. The internal hysteresis creates two trip points, one for the rising input voltage and one for the falling input voltage. The difference between the trip points is the hysteresis. With internal hysteresis, when the comparator’s input voltages are equal, the hysteresis effectively causes one comparatorinput voltage to move quickly past the other, thus taking the input out of the region where oscillation occurs. Standard comparators require hysteresis to be added with external resistors. The fixed internal hysteresis eliminates these resistors. 10105418 FIGURE 1. Input and Output Waveforms, Non-Inverting Input Varied www.national.com 8 LMV7219 Additional Hysteresis If additional hysteresis is desired, this can be done with the addition of three resistors using positive feedback, as shown in Figure 2. The positive feedback method slows the comparator response time. Calculate the resistor values as follows: 1) Select R3. The current through R3 should be greater than the input bias current to minimize errors. The current through R3 (IF) at the trip point is (VREF - VOUT) /R3. Consider the two possible output states when solving for R3, and use the smaller of the two resulting resistor values. The two formulas are: (when VOUT = 0) R3 = VREF/IF (VOUT = VCC) R3 = VCC - VREF /IF 2) Choose a hysteresis band required (VHB). 3) Calculate R1, where R1 = R3 X(VHB/VCC) 4) Choose the trip point for VIN rising. This is the threshold voltage (VTHR) at which the comparator switches from low to high as VIN rises about the trip point. 5) Calculate R2 as follows: 0.1µF ceramic should be placed as close as possible to V+ pin. An additional 2.2µF tantalum capacitor may be required for extra noise reduction. 2. Keep all leads short to reduce stray capacitance and lead inductance. It will also minimize unwanted parasitic feedback around the comparator. 3. The device should be soldered directly to the PC board instead of using a socket. 4. Use a PC board with a good, unbroken low inductance ground plane. Make sure ground paths are low-impedance, especially were heavier currents are flowing. 5. Input traces should be kept away from output traces. This can be achieved by running a topside ground plane between the output and inputs. 6. Run the ground trace under the device up to the bypass capacitor to shield the inputs from the outputs. 7. To prevent parasitic feedback when input signals are slow-moving, a small capacitor of 1000pF or less can be placed between the inputs. It can also help eliminate oscillations in the transition region. However, this capacitor can cause some degradation to tpd when the source impedance is low. Zero-Crossing Detector 6) Verify the trip voltage and hysteresis as follows: The inverting input is connected to ground and the noninverting input is connected to 100mVp-p signal. As the signal at the non-inverting input crosses 0V, the comparator’s output Changes State. 10105422 This method is recommended for additional hysteresis of up to a few hundred millivolts. Beyond that, the impedance of R3 is low enough to affect the bias string and adjustment of R1 may be also required. FIGURE 3. Zero-Crossing Detector Threshold Detector Instead of tying the inverting input to 0V, the inverting input can be tied to a reference voltage. The non-inverting input is connected to the input. As the input passes the VREF threshold, the comparator’s output changes state. 10105421 FIGURE 2. Additional Hysteresis Circuit Layout and Bypassing The LMV7219 requires high-speed layout. Follow these layout guidelines: 1. Power supply bypassing is critical, and will improve stability and transient response. A decoupling capacitor such as 10105423 FIGURE 4. Threshold Detector 9 www.national.com LMV7219 Crystal Oscillator A simple crystal oscillator using the LMV7219 is shown below. Resistors R1 and R2 set the bias point at the comparator’s non-inverting input. Resistors R3, R4 and C1 sets the inverting input node at an appropriate DC average level based on the output. The crystal’s path provides resonant positive feedback and stable oscillation occurs. The output duty cycle for this circuit is roughly 50%, but it is affected by resistor tolerances and to a lesser extent by the comparator offset. IR Receiver The LMV7219 is an ideal candidate to be used as an infrared receiver. The infrared photo diode creates a current relative to the amount of infrared light present. The current creates a voltage across RD. When this voltage level cross the voltage applied by the voltage divider to the inverting input, the output transitions. 10105425 10105424 FIGURE 6. IR Receiver FIGURE 5. Crystal Oscillator www.national.com 10 LMV7219 Physical Dimensions inches (millimeters) unless otherwise noted 5-Pin SC70-5 NS Package Number MAA05A 11 www.national.com LMV7219 7 nsec, 2.7V to 5V Comparator with Rail-to-Rail Output Physical Dimensions inches (millimeters) unless otherwise noted (Continued) 5-Pin SOT23-5 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. For the most current product information visit us at www.national.com. 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. 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