Table 1A. Electrical Specifications (Vs = 1.65 V to 5.5 V, Ta = -40 °C to 85 °C [-40 °F to 185 °F], Typ. at 1.8 V, 25 °C [77 °F] unless otherwise specified.)
Max.
5.5
5
5
—
8
0.8
1
8
180
6640
6350
0.15
Vs
Unit
V
mA
µs
Sleep current
µA
Sleep time
Average current:
SM351LT
SM353LT
Output voltage:
low (V
OL
)
high (V
OH
)
ms
nA
load current = 100 µA
V
NOTICE
These magnetoresistive sensor ICs may have an initial output in either
the ON or OFF state if powered up with an applied magnetic field in
the differential zone (applied magnetic field >Brp and <Bop). Honeywell
recommends allowing 10 μs for output voltage to stabilize after supply
voltage has reached its final rated value.
Table 1B. Electrical Specifications (Vs = 1.8 V, Ta = 25 °C [77 °F].)
Characteristic
Awake current:
SM351LT
SM353LT
Awake time
Sleep current
Sleep time
Average current:
SM351LT
SM353LT
Condition
—
—
—
—
0.015% duty cycle, typ.
Min.
—
—
—
—
90
—
—
Typ.
1
0.8
15
0.2
100
350
350
Max.
1.12
0.87
—
0.59
120
620
600
Unit
mA
µs
µA
ms
nA
NOTICE
The sensor will turn LOW when the magnetic field is present and switch to
HIGH when the field is removed. The sensor will latch and hold the state
during the sleep “mode”.
Sensing and Control
Magnetoresistive Sensor ICs
Nanopower Series
Table 2. Magnetic Specifications (Vs = 1.65 V to 5.5 V, Ta = -40 °C to 85 °C [-40 °F to 185 °F]
Characteristic
SM351LT:
operate (positive)
release (positive)
hysteresis
SM353LT:
operate (positive)
release (positive)
hysteresis
Min.
3
2
Typ.
7
5
2
14
10
4
Max.
11
—
—
20
—
—
Issue C
50094459
Unit
Gauss
*
6
3
Gauss
*
*At 1.65 V and -40 °C, the hysteresis can reach 0.1 Gauss.
NOTICE
The magnetic field strength (Gauss) required to cause the switch to
change state (operate and release) will be as specified in the
magnetic characteristics. To test the switch against the specified
magnetic characteristics, the switch must be placed in a uniform
magnetic field.
Table 3. Absolute Maximum Ratings
Characteristic
Operating temperature
Soldering temperature
Supply voltage (Vs)
Output (load) current
Condition
ambient
ambient applied for <10 s
—
—
Min.
-40 [-40]
—
-0.5
—
Typ.
—
—
—
—
Max.
85 [185]
265 [509]
6
5
Unitt
°C [°F]
°C [°F]
V
mA
NOTICE
Absolute maximum ratings are the extreme limits that the device will withstand without damage to the
device. However, the electrical and mechanical characteristics are not guaranteed as the maximum limits
(above recommended operating conditions) are approached, nor will the device necessarily operate at
absolute maximum ratings.
Figure 1. Block/Electrical Diagram
CAUTION
ELECTROSTATIC
SENSITIVE
DEVICES
DO NOT OPEN OR HANDLE
EXCEPT AT A
STATIC FREE WORKSTATION
ESD SENSITIVITY:
CLASS 2
V
S+
Clock
Counter
Decoder
AMR
0
Gnd-
Output
Flip Q
D Flop
V
Out
Dual
Threshold
Comparator
2
Honeywell Sensing and Control
Magnetoresistive Sensor ICs
Nanopower Series
Figure 2. Alignment of the Magnet to the Omnipolar Magnetoresistive Sensor IC
Ideal alignment: The magnet is aligned in the same plane as the sensor IC.
Figure 2.A
The magnetic flux lines stay horizontal as the magnet approaches the
sensor IC (see Figure 2.A).
Issue C
50094459
SM351LT,
SM353LT
Sensor IC
Magnet
Magnet movement
Offset alignment: The magnet is not aligned in the same plane as the sensor IC.
Parallel magnet approach to the sensor IC may cause dead zones.
Dead zones may occur when the majority of the magnet’s magnetic
flux lines become vertical as it approaches the sensor IC, turning
the sensor IC to ON, then OFF, then ON (see Figure 2.B).
Figure 2.B
Magnet
Magnet
SM351LT,
SM353LT
Sensor IC
Magnet movement
Perpendicular magnet approach to the sensor IC eliminates possible dead zones.
The sensor IC detects the approaching magnet’s horizontal magnetic flux lines, turning the sensor IC to ON. The sensor IC stays ON as the
magnet continues to approach. When the magnet is located directly over the sensor IC, all magnetic flux lines are now horizontal (see Figure
2.C). Note: This alignment decreases the magnetic flux strength at the sensor IC.
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