lm1815mx National Semiconductor Corporation, lm1815mx Datasheet

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lm1815mx

Manufacturer Part Number
lm1815mx
Description
Adaptive Variable Reluctance Sensor Amplifier
Manufacturer
National Semiconductor Corporation
Datasheet

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© 2005 National Semiconductor Corporation
LM1815
Adaptive Variable Reluctance Sensor Amplifier
General Description
The LM1815 is an adaptive sense amplifier and default
gating circuit for motor control applications. The sense am-
plifier 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 pro-
cessed (delayed) externally and returned to the LM1815. 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
150mV
Connection Diagram
P-P
.
See NS Package Number M14A or N14A
DS007893
Order Number LM1815M or LM1815N
Top View
Features
n Adaptive hysteresis
n Single supply operation
n Ground referenced input
n True zero crossing timing reference
n Operates from 2V to 12V supply voltage
n Handles inputs from 100 mV
n CMOS compatible logic
Applications
n Position sensing with notched wheels
n Zero crossing switch
n Motor speed control
n Tachometer
n Engine testing
external resistor
00789301
P-P
to over 120V
www.national.com
March 2005
P-P
with

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lm1815mx Summary of contents

Page 1

... Minimum input signal is 150mV . P-P Connection Diagram © 2005 National Semiconductor Corporation Features n Adaptive hysteresis n Single supply operation n Ground referenced input n True zero crossing timing reference n Operates from 2V to 12V supply voltage ...

Page 2

Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage Power Dissipation (Note 2) Operating Temperature Range Electrical Characteristics Parameter Operating Supply Voltage Supply Current Pin 3 ...

Page 3

Typical Performance Characteristics Mode 1 Minimum Arming Threshold vs Temperature Mode 3 Minimum Arming Threshold vs Temperature Mode 2 Minimum Arming Threshold Mode 2 Minimum Arming Threshold 00789305 Mode 1 Minimum Arming Threshold 00789307 00789309 3 vs ...

Page 4

Typical Performance Characteristics Pin 10kΩ SIGNAL IN Pin 50kΩ SIGNAL IN Peak Detector Charge Current vs Temperature www.national.com (Continued 00789311 Pin 3 ...

Page 5

Typical Performance Characteristics Peak Detector Voltage vs Pin Mode 1 IN (Continued) Peak Detector Voltage vs Pin 3 V 00789317 Peak Detector Voltage vs Pin Mode 3 IN 00789319 5 , Mode 2 IN ...

Page 6

Truth Table Signal Input Pin 3 ± Pulses X X ± Pulses www.national.com RC Input Timing Timing Select Input Pin 14 Pin 11 Pin FIGURE 1. LM1815 ...

Page 7

7 www.national.com ...

Page 8

Application Hints INPUT VOLTAGE CLAMP The signal input voltage at pin 3 is internally clamped. Cur- rent limit for the Input pin is provided by an external resistor which should be selected to allow a peak current of normal operation. ...

Page 9

Application Hints (Continued) 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 ...

Page 10

Physical Dimensions unless otherwise noted www.national.com inches (millimeters) 14-Lead Small Outline Circuit (M) Order Number LM1815M NS Package Number M14A 10 ...

Page 11

Physical Dimensions inches (millimeters) unless otherwise noted (Continued) 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 ...

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