NSC LM1815MXEP

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
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LM1815EP Enhanced Plastic Adaptive Variable Reluctance Sensor Amplifier
OBSOLETE
LM1815EP Enhanced Plastic
Connection Diagram
20090501
Top View
See NS Package Number M14A or N14A
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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.
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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
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20090508
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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
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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
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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
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20090504
LM1815EP Enhanced Plastic
Schematic Diagram
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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)
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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:
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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
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LM1815EP Enhanced Plastic Adaptive Variable Reluctance Sensor Amplifier
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