LM1815 ARTSCHIP | Alldatasheet
Document overview
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Technical content
Features
z True zero crossing timing reference z Operates from 2V to 12V supply voltage z Handles inputs from 100 mV to over 120V with external resistor z CMOS compatible logic
Applications
z Position sensing with notched wheels z Zero crossing switch z Motor speed control z Tachometer z Engine testing Connection Diagram Top View Order Number LM1815M or LM1815N See NS Package Number M14A or N14A Truth Table Signal Input Input Select Timing Input Gated Output Pulses L X Pulses X H Pulses Pulses
www.artschip.com 2 Absolute Maximum Ratings If Military/Aerospace specified devices are required. Please contact the National Semiconductor Sales office/Distributors for availability and specifications. S u p p l y V o l t a g e 1 2 V P o w e r D i s s i p a t i o n ( N o t e 1 ) 1 2 5 0 m W Operating Temperature Range -40 ¥ to +125 ¥ Storage Temperature Range -65 ¥ to +150 ¥ J u n c t i o n T e m p e r a t u r e ( N o t e 2 ) + 1 2 5¥ Input Current ±30mA Lead Temperature (Soldering, 10 sec.) 260 ¥ Electrical Characteristics (TA=25¥, Vcc=10V, unless otherwise specified, see Figure 1) Parameter Conditions Min Typ Max Units Operating Supply Voltage 2.5 10 12 V Supply Current f IN=500Hz. Pin 9=2V, Pin 11=0.8V 3.6 6 mA Reference Pulse Width f IN=1 Hz to 2kHz 70 100 130 µs Input Bias Current V IN=2V, (Pin 9 and Pin 11) 5 µA Input Bias Current V IN=0V dc, (Pin3) 200 nA Input Impedance V IN=5Vrms, (Note 3) 12 20 28 k Ω Zero Crossing Threshold V IN=100mVp-p, (Pin 3) 25 mV Logic Threshold (Pin 9 and Pin 11) 0.8 1.1 2.0 V VOUT High R L=1kΩ, (Pin 10) 7.5 8.6 V VOUT Low I SINK=0.1mA,(Pin 10) 0.3 0.4 V Pin 5 Open, VIN ≤135mVp-p 30 45 60 mV Pin 5 Open, VIN≥230mVp-p 40 80 90 % of V3 Pk Pin 5 to V+ 200 mV Input Arming Threshold Pin 5 to Gnd -25 25 mV Output Leakage Pin 12 V 12=11V 0.01 10 µA Saturation Voltage P12 I 12=2mA 0.2 0.4 V Note 1: For operation at el evated temperatures, the devic e must be derated based on a 125 ¥ maximum junction temperature and a thermal resistance of 80¥/W (DIP), 120¥/W (SO-14) junction to ambient. Note 2: Temporary excursions to 150¥ can be tolerated. Note 3: Measured at input to external 18kΩ resistor. IC contains 1kΩ in series with a diode to attenuate the input signal.
FIGURE 1. LM1815 Adaptive Sense Amplifier
www.artschip.com 4 Schematic Diagram
www.artschip.com 5 Application Hints Input Clamp The signal input at pin 3 is inter nally clamped. Current limit 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 1 k Ω resistor and series diode, while an active clamp limits pin 3 to -350 mV for negative inputs (see R4, Q12, Q11 in internal schematic diagram). Operation of Zero Crossing Detector The LM1815 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 LM1815 cannot be triggered until the input signal has crossed an “arming” threshold on the positive-going portion 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: MODE 1, Pin 5 open. The adaptive mode is selected by leaving pin 5 open circuit. For input signals of less than 135 mVp-p, the input arming threshold is typically 45 mV. Under these conditions the input signa l must first cross the 45 mV 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 30 mV peak (minimum rating in Electrical Characteristics), the one shot is guaranteed to not trigger. Input signals of greater th an 230 mVp-p cause the arming threshold to track at 80% of the peak input voltage. A peak detector (pin 7) stores a value relative to the positive input peaks to establish to 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 to track decreases in the input signal. Note that since the input 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. MODE 2, Pin 5 connected to V+. The input arming threshold is fixed at 200 mV minimum when pin 5 is connected to the positive supply. The chip has no output for signals of less than 200 mV peak, and triggers on the next negative going zero crossing when the threshold is exceeded. 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 zero crossing triggers it . The one shot timing is set by a resistor and capacitor connected to pin 14. The output pulse width is Pulse width = 0.673 RC (1) 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 o ne 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, pin 9, 11 and 12 are TTL compatible. Pin 10 is not guaranteed to drive a TTL load. Pin 1. 4. 6 and 13 have no internal connections and can be grounded.
www.artschip.com 6 Physical Dimensions inches (millimeters) 14-Lead Small Outline Integrated Circuit (M) Order Number LM1815M
www.artschip.com 7 Physical Dimensions inches (millimeters) (Continued) Molded Dual-In-Line Package (N) Order Number LM1815N