US4881
Bipolar Hall Switch
Low Voltage & Very High Sensitivity
9 Detailed General Description
Based on mixed signal CMOS technology, Melexis US4881 is a Hall-effect device with very high magnetic
sensitivity. It allows using generic magnets, weak magnets or larger air gap.
The chopper-stabilized amplifier uses switched capacitor techniques to suppress the offset generally
observed with Hall sensors and amplifiers. The CMOS technology makes this advanced technique possible
and contributes to smaller chip size and lower current consumption than bipolar technology. The small chip
size is also an important factor to minimize the effect of physical stress.
This combination results in more stable magnetic characteristics and enables faster and more precise design.
The operating voltage from 2.2V to 18V, low current consumption and large choice of operating temperature
range according to “L”, “K” and “E” specification make this device suitable for automotive, industrial and
consumer low voltage applications.
The output signal is open-drain type. Such output allows simple connectivity with TTL or CMOS logic by using
a pull-up resistor tied between a pull-up voltage and the device output.
10 Unique Features
The US4881 exhibits bipolar magnetic switching characteristics. Therefore, it operates with both south and
north poles.
Typically, the device behaves as a latch with symmetric
operating and release switching points (B
OP
=|B
RP
|). This means
magnetic fields with equivalent strength and opposite direction
drive the output high and low.
Removing the magnetic field (B→0) keeps the output in its
previous state. This latching property defines the device as a
magnetic memory.
Latch characteristic
Depending on the magnetic switching points, the device may also behave as a unipolar positive switch (B
OP
and B
RP
strictly positive) or negative switch (B
OP
and B
RP
strictly negative). That is the output can be set high
and low by only using one magnetic pole. In such case, removing the magnetic field changes the output level.
Unipolar positive switch characteristic
Unipolar negative switch characteristic
In latch, positive or negative switch behaviour, a magnetic hysteresis B
HYST
keeps B
OP
and B
RP
separated by
a minimal value. This hysteresis prevents output oscillation near the switching point.
3901004881
Rev 011
Page 5 of 11
Data Sheet
Feb/06
MELEXIS [ Melexis Microelectronic Systems ]
