National Semiconductor LM1815 Technical data
LM1815
Adaptive Variable Reluctance Sensor Amplifier
LM1815 Adaptive Variable Reluctance Sensor Amplifier
April 2003
General Description
The LM1815 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 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
P-P
.
150mV
Connection Diagram
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
external resistor
n CMOS compatible logic
to over 120V
P-P
Applications
n Position sensing with notched wheels
n Zero crossing switch
n Motor speed control
n Tachometer
n Engine testing
P-P
with
Top View
Order Number LM1815M or LM1815N
See NS Package Number M14A or N14A
© 2003 National Semiconductor Corporation DS007893 www.national.com
00789301
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
LM1815
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage 12V
Power Dissipation (Note 2) 1250 mW
Operating Temperature Range −40˚C ≤ T
≤ +125˚C
A
Storage Temperature Range −65˚C ≤ T
≤ +150˚C
J
Junction Temperature +150˚C
Input Current
±
30 mA
Lead Temperature
(Soldering, 10 sec.) 260˚C
Electrical Characteristics (T
= 25˚C, VCC= 10V, unless otherwise specified, see Figure 1)
A
Parameter Conditions Min Typ Max Units
Operating Supply Voltage 2.5 10 12 V
Supply Current Pin 3 = -0.1V, Pin 9 = 2V, Pin 11 = 0.8V 3.6 6 mA
Reference Pulse Width f
Logic Input Bias Current V
Signal Input Bias Current V
= 1Hz to 2kHz, R = 150kΩ, C = 0.001µF 70 100 130 µs
IN
= 2V, (Pin 9 and Pin 11) 5 µA
IN
= 0V dc, (Pin 3) -200 nA
IN
Logic Threshold (Pin 9 and Pin 11) 0.8 1.1 2.0 V
V
High RL=1kΩ, (Pin 10) 7.5 8.6 V
OUT
V
Low I
OUT
Output Leakage Pin 12 V
Saturation Voltage P12 I
Input Zero Crossing Threshold All Modes, V
Minimum Input Arming
Threshold
Adaptive Input Arming
Threshold
Note 1: “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 2: 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 3: Tested per Figure 1, V
Note 4: The Min/Typ Max limits are relative to the positive voltage peak seen at V
SIGNAL
= 0.1mA, (Pin 10) 0.3 0.4 V
SINK
= 11V 0.01 10 µA
12
= 2mA 0.2 0.4 V
12
= 1V pk-pk -25 0 25 mV (Note 4)
SIGNAL
Mode 1, Pin 5 = Open 30 45 60 mV (Note 4)
Mode 2, Pin5=V
CC
200 300 450 mV (Note 4)
Mode 3, Pin 5 = Gnd -25 0 25 mV (Note 4)
Mode 1, Pin 5 = Open
V
≥ 230mV pk-pk (Note 3)
SIGNAL
Mode 2, Pin5=V
V
≥ 1.0V pk-pk (Note 3)
SIGNAL
Mode 3, Pin5=Gnd
V
is a Sine Wave; F
≥ 150mV pk-pk (Note 3)
SIGNAL
SIGNAL
CC
is 1000Hz.
IN
Pin 3.
40 80 90 % (Note 4)
80 % (Note 4)
80 % (Note 4)
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Typical Performance Characteristics
LM1815
Mode 1 Minimum Arming Threshold
vs Temperature
Mode 3 Minimum Arming Threshold
vs Temperature
00789305
Mode 2 Minimum Arming Threshold
vs Temperature
Mode 1 Minimum Arming Threshold
vs V
CC
00789306
Mode 2 Minimum Arming Threshold
vs V
CC
00789307 00789308
Pin3V
vs V
00789309 00789310
IN
SIGNAL
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Typical Performance Characteristics (Continued)
LM1815
vs V
vs V
Pin3V
SIGNAL,RIN
Pin3V
SIGNAL,RIN
IN
= 10kΩ
IN
= 50kΩ
Pin3V
vs V
SIGNAL,RIN
00789311 00789312
IN
= 20kΩ
Pin 3 Bias Current
vs Temperature
00789313 00789314
Peak Detector Charge Current
vs Temperature
00789315 00789316
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Peak Detector Charge Current
vs V
CC
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