July 23, 2010 LM1815EP Enhanced Plastic Adaptive Variable Reluctance Sensor Amplifier General Description Features The LM1815EP is an adaptive sense amplifier and default gating circuit for motor control applications. The sense amplifier provides a one-shot pulse output whose leading edge coincides with the negative-going zero crossing of a ground referenced input signal such as from a variable reluctance magnetic pick-up coil. In normal operation, this timing reference signal is processed (delayed) externally and returned to the LM1815EP. A Logic input is then able to select either the timing reference or the processed signal for transmission to the output driver stage. The adaptive sense amplifier operates with a positive-going threshold which is derived by peak detecting the incoming signal and dividing this down. Thus the input hysteresis varies with input signal amplitude. This enables the circuit to sense in situations where the high speed noise is greater than the low speed signal amplitude. Minimum input signal is 150mVP-P. ENHANCED PLASTIC • Extended Temperature Performance of −40°C to +125°C • Baseline Control - Single Fab & Assembly Site • Process Change Notification (PCN) • Qualification & Reliability Data • Solder (PbSn) Lead Finish is standard • Enhanced Diminishing Manufacturing Sources (DMS) Support ■ ■ ■ ■ ■ ■ Adaptive hysteresis Single supply operation Ground referenced input True zero crossing timing reference Operates from 2V to 12V supply voltage Handles inputs from 100 mVP-P to over 120VP-P with external resistor ■ CMOS compatible logic Applications ■ Selected Military Applications ■ Selected Avionics Applications Ordering Information PART NUMBER VID PART NUMBER NS PACKAGE NUMBER (Note 3) LM1815MXEP V62/04634-01 M14A (Note 1, Note 2) TBD TBD Note 1: For the following (Enhanced Plastic) versions, check for availability: LM1815MEP, LM1815NEP. Parts listed with an "X" are provided in Tape & Reel and parts without an "X" are in Rails. Note 2: FOR ADDITIONAL ORDERING AND PRODUCT INFORMATION, PLEASE VISIT THE ENHANCED PLASTIC WEB SITE AT: www.national.com/ mil Note 3: Refer to package details under Physical Dimensions © 2010 National Semiconductor Corporation 200905 200905 Version 2 Revision 1 www.national.com Print Date/Time: 2010/07/23 13:58:32 LM1815EP Enhanced Plastic Adaptive Variable Reluctance Sensor Amplifier OBSOLETE LM1815EP Enhanced Plastic Connection Diagram 20090501 Top View See NS Package Number M14A or N14A www.national.com 2 200905 Version 2 Revision 1 Print Date/Time: 2010/07/23 13:58:32 Storage Temperature Range If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Junction Temperature Input Current Lead Temperature (Soldering, 10 sec.) Supply Voltage Power Dissipation (Note 5) Operating Temperature Range 12V 1250 mW −65°C ≤ TJ ≤ +150°C +150°C ±30 mA 260°C −40°C ≤ TA ≤ +125°C Electrical Characteristics Parameter (TA = 25°C, VCC = 10V, unless otherwise specified, see Figure 1) Conditions Min Operating Supply Voltage 2.5 Typ Max 10 12 V 3.6 6 mA 100 130 µs 5 µA Supply Current Pin 3 = -0.1V, Pin 9 = 2V, Pin 11 = 0.8V Reference Pulse Width fIN = 1Hz to 2kHz, R = 150kΩ, C = 0.001µF Logic Input Bias Current VIN = 2V, (Pin 9 and Pin 11) Signal Input Bias Current VIN = 0V dc, (Pin 3) Logic Threshold (Pin 9 and Pin 11) 0.8 1.1 VOUT High RL = 1kΩ, (Pin 10) 7.5 8.6 VOUT Low ISINK = 0.1mA, (Pin 10) 0.3 Output Leakage Pin 12 V12 = 11V Saturation Voltage P12 I12 = 2mA Input Zero Crossing Threshold All Modes, VSIGNAL = 1V pk-pk Mode 1, Pin 5 = Open 70 Units -200 nA 2.0 V V 0.4 V 0.01 10 µA 0.2 0.4 V -25 0 25 mV (Note 7) 30 45 60 mV (Note 7) Minimum Input Arming Threshold Mode 2, Pin 5 = VCC 200 300 450 mV (Note 7) Mode 3, Pin 5 = Gnd -25 0 25 mV (Note 7) 40 80 90 %(Note 7) Mode 1, Pin 5 = Open VSIGNAL ≥ 230mV pk-pk (Note 6) Adaptive Input Arming Threshold Mode 2, Pin 5 = VCC VSIGNAL ≥ 1.0V pk-pk (Note 6) Mode 3, Pin 5 = Gnd VSIGNAL ≥ 150mV pk-pk (Note 6) 80 %(Note 7) 80 %(Note 7) Note 4: “Absolute Maximum Ratings” are those values beyond which the safety of the device cannot be guaranteed. They are not meant to imply that the devices should be operated at these limits. The table of “Electrical Characteristics” specifies conditions of device operation. Note 5: For operation at elevated temperatures, the device must be derated based on a 150°C maximum junction temperature and a thermal resistance of 80° C/W (DIP), 120°C/W (SO-14) junction to ambient. Note 6: Tested per Figure 1, VSIGNAL is a Sine Wave; FSIGNAL is 1000Hz. Note 7: The Min/Typ Max limits are relative to the positive voltage peak seen at VIN Pin 3. 3 200905 Version 2 Revision 1 Print Date/Time: 2010/07/23 13:58:32 www.national.com LM1815EP Enhanced Plastic Absolute Maximum Ratings (Note 4) LM1815EP Enhanced Plastic Typical Performance Characteristics Mode 1 Minimum Arming Threshold vs Temperature Mode 2 Minimum Arming Threshold vs Temperature 20090505 20090506 Mode 3 Minimum Arming Threshold vs Temperature Mode 1 Minimum Arming Threshold vs VCC 20090507 www.national.com 20090508 4 200905 Version 2 Revision 1 Print Date/Time: 2010/07/23 13:58:32 LM1815EP Enhanced Plastic Mode 2 Minimum Arming Threshold vs VCC Pin 3 VIN vs VSIGNAL 20090509 20090510 Pin 3 VIN vs VSIGNAL, RIN = 10kΩ Pin 3 VIN vs VSIGNAL, RIN = 20kΩ 20090511 20090512 Pin 3 VIN vs VSIGNAL, RIN = 50kΩ Pin 3 Bias Current vs Temperature 20090514 20090513 5 200905 Version 2 Revision 1 Print Date/Time: 2010/07/23 13:58:32 www.national.com LM1815EP Enhanced Plastic Peak Detector Charge Current vs Temperature Peak Detector Charge Current vs VCC 20090515 20090516 Peak Detector Voltage vs Pin 3 VIN, Mode 1 Peak Detector Voltage vs Pin 3 VIN, Mode 2 20090517 20090518 Peak Detector Voltage vs Pin 3 VIN, Mode 3 20090519 www.national.com 6 200905 Version 2 Revision 1 Print Date/Time: 2010/07/23 13:58:32 LM1815EP Enhanced Plastic Truth Table Signal Input Pin 3 RC Timing Pin 14 Input Select Pin 11 Timing Input Pin 9 Gated Output Pin 10 ± Pulses RC X X L X Pulses = RC H H H X X H L L ± Pulses L L L Zero Crossing 20090502 FIGURE 1. LM1815EP Adaptive Sense Amplifier 7 200905 Version 2 Revision 1 Print Date/Time: 2010/07/23 13:58:32 www.national.com 20090504 LM1815EP Enhanced Plastic Schematic Diagram www.national.com 8 200905 Version 2 Revision 1 Print Date/Time: 2010/07/23 13:58:32 LM1815EP Enhanced Plastic Application Hints 20090503 FIGURE 2. LM1815EP Oscillograms of the waveform. The arming circuit is reset when the chip is triggered, and subsequent zero crossings are ignored until the arming threshold is exceeded again. This threshold varies depending on the connection at pin 5. Three different modes of operation are possible: INPUT VOLTAGE CLAMP The signal input voltage at pin 3 is internally clamped. Current limit for the Input pin is provided by an external resistor which should be selected to allow a peak current of ±3 mA in normal operation. Positive inputs are clamped by a 1kΩ resistor and series diode (see R4 and Q12 in the internal schematic diagram), while an active clamp limits pin 3 to typically 350mV below Ground for negative inputs (see R2, R3, Q10, and Q11 in the internal schematic diagram). Thus for input signal transitions that are more than 350mV below Ground, the input pin current (up to 3mA) will be pulled from the V+ supply. If the V + pin is not adequately bypassed the resulting voltage ripple at the V+ pin will disrupt normal device operation. Likewise, for input signal transitions that are more than 500mV above Ground, the input pin current will be dumped to Ground through device pin 2. Slight shifts in the Ground potential at device pin 2, due to poor grounding techniques relative to the input signal ground, can cause unreliable operation. As always, adequate device grounding, and V+ bypassing, needs to be considered across the entire input voltage and frequency range for the intended application. MODE 1, PIN 5 OPEN The adaptive mode is selected by leaving device pin 5 open circuit. For input signals of less than ±135mV (i.e. 270 mVpp) and greater than typically ±75mV (i.e. 150mVp-p), the input arming threshold is typically at 45mV. Under these conditions the input signal must first cross the 45mV threshold in the positive direction to arm the zero crossing detector, and then cross zero in the negative direction to trigger it. If the signal is less than 30mV peak (minimum rating in Electrical Characteristics), the one shot is guaranteed to not trigger. Input signals of greater than ±230mV (i.e. 460 mVp-p) will cause the arming threshold to track at 80% of the peak input voltage. A peak detector capacitor at device pin 7 stores a value relative to the positive input peaks to establish the arming threshold. Input signals must exceed this threshold in the positive direction to arm the zero crossing detector, which can then be triggered by a negative-going zero crossing. The peak detector tracks rapidly as the input signal amplitude increases, and decays by virtue of the resistor connected externally at pin 7 track decreases in the input signal. If the input signal amplitude falls faster than the voltage stored on the peak detector capacitor there may be a loss of output signal until the capacitor voltage has decayed to an appropriate level. Note that since the input voltage is clamped, the waveform observed at pin 3 is not identical to the waveform observed at the variable reluctance sensor. Similarly, the voltage stored at pin 7 is not identical to the peak voltage appearing at pin 3. INPUT CURRENT LIMITING As stated earlier, current limiting for the Input pin is provided by a user supplied external resistor. For purposes of selecting the appropriate resistor value the Input pin should be considered to be a zero ohm connection to ground. For applications where the input voltage signal is not symmetrical with relationship to Ground the worst case voltage peak should be used. Minimum Rext = [(Vin peak)/3mA] In the application example shown in figure 1 (Rext = 18kΩ) the recommended maximum input signal voltage is ±54V (i.e. 108Vp-p). OPERATION OF ZERO CROSSING DETECTOR The LM1815EP is designed to operate as a zero crossing detector, triggering an internal one shot on the negative-going edge of the input signal. Unlike other zero crossing detectors, the LM1815EP cannot be triggered until the input signal has crossed an "arming" threshold on the positive-going portion MODE 2, PIN 5 CONNECTED TO V+ The input arming threshold is fixed at 200mV minimum when device pin 5 is connected to the positive supply. The chip has no output for signals of less than ±200 mV (i.e. 400mVp-p) 9 200905 Version 2 Revision 1 Print Date/Time: 2010/07/23 13:58:32 www.national.com LM1815EP Enhanced Plastic and triggers on the next negative-going zero crossing when the arming threshold is has been exceeded. Fin(max) = 1/(1.346 x R x C) MODE 3, PIN 5 GROUNDED With pin 5 grounded, the input arming threshold is set to 0V, ±25mV maximum. Positive-going zero crossings arm the chip, and the next negative-going zero crossing triggers it. This is the very basic form of zero-crossing detection. In the application example shown in figure 1 (R=150kohms, C=0.001µF) the recommended maximum input frequency will typically be 5kHz. Operating with input frequencies above the recommended Fin (max) value may result in unreliable performance of the One Shot circuitry. For those applications where the One Shot circuit is not required, device pin 14 can be tied directly to Ground. ONE SHOT TIMING The one shot timing is set by a resistor and capacitor connected to pin 14. The recommended maximum resistor value is 150kohms. The capacitor value can be changed as needed, as long as the capacitor type does not present any signfigant leakage that would adversely affect the RC time constant. The output pulse width is: pulse width = 0.673 x R x C LOGIC INPUTS In some systems it is necessary to externally generate pulses, such as during stall conditions when the variable reluctance sensor has no output. External pulse inputs at pin 9 are gated through to pin 10 when Input Select (pin 11) is pulled high. Pin 12 is a direct output for the one shot and is unaffected by the status of pin 11. Input/output pins 9, 11, 10, and 12 are all CMOS logic compatible. In addition, pins 9, 11, and 12 are TTL compatible. Pin 10 is not guaranteed to drive a TTL load. Pins 1, 4, 6 and 13 have no internal connections and can be grounded. (1) For a given One Shot pulse width, the recommended maximum input signal frequency is: www.national.com 10 200905 Version 2 Revision 1 (2) Print Date/Time: 2010/07/23 13:58:32 LM1815EP Enhanced Plastic Physical Dimensions inches (millimeters) unless otherwise noted 14-Lead Small Outline Circuit (M) NS Package Number M14A Molded Dual-In-Line Package (N) NS Package Number N14A 11 200905 Version 2 Revision 1 Print Date/Time: 2010/07/23 13:58:32 www.national.com LM1815EP Enhanced Plastic Adaptive Variable Reluctance Sensor Amplifier 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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