Two-Wire True Zero-Speed Miniature Differential
Peak-Detecting Sensor IC with Continuous Calibration
A1642
10
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Power Supply Protection
The device contains an on-chip regulator and can operate over
a wide V
CC
range. For devices that need to operate from an
unregulated power supply, transient protection must be added
externally. For applications using a regulated line, EMI/RFI pro-
tection may still be required. Contact Allegro Microsystems for
information on the circuitry needed for compliance with various
EMC speci cations. Refer to gure 7 for an example of a basic
application circuit.
Undervoltage Lockout
When the supply voltage falls below the undervoltage lockout
voltage, V
CC(UV)
, the device enters Reset, where the output state
returns to the Power-On State (POS) until suf cient V
CC
is sup-
plied. I
CC
levels may not meet datasheet limits when
V
CC
< V
CC(min)
.
Assembly Description
This device is integrally molded into a plastic body that has been
optimized for size, ease of assembly, and manufacturability.
High operating temperature materials are used in all aspects of
construction.
Diagnostics
The regulated current output is con gured for two wire appli-
cations, requiring one less wire for operation than do switches
with the more traditional open-collector output. Additionally,
the system designer inherently gains diagnostics because there is
always output current flowing, which should be in either of two
narrow ranges, shown in figure 8 as I
CC(High)
and I
CC(Low)
. Any
current level not within these ranges indicates a fault condi-
tion. If I
CC
> I
CC(High)max
, then a short condition exists, and if
I
CC
< I
CC(low)min
, then an open condition exists. Any value of I
CC
between the allowed ranges for I
CC(High)
and I
CC(Low)
indicates a
general fault condition.
Figure 7: Typical Application Circuit
A1642
VCC
GND
V+
0.01
1
4
礔
ECU
Pins 2 and 3 floating
R
100 ?/DIV>
SENSE
C
BYP
Figure 8: Diagnostic Characteristics of Supply Current Values
I
CC(High)max
I
CC(High)min
Range for Valid I
CC(HIGH)
Range for Valid I
CC(LOW)
I
CC(Low)max
I
CC(Low)min
0
+mA
A
A
Short
Fault
Open