tle4921-3u Infineon Technologies Corporation, tle4921-3u Datasheet - Page 4

• Manufacturer Part Number: tle4921-3u
• Description: Differential Hall Sensor
• Manufacturer: Infineon Technologies Corporation

TLE 4921-3U
Functional Description
The Differential Hall Sensor IC detects the motion and position of ferromagnetic and
permanent magnet structures by measuring the differential flux density of the magnetic
field. To detect ferromagnetic objects the magnetic field must be provided by a back
biasing permanent magnet (south or north pole of the magnet attached to the rear
unmarked side of the IC package).
Using an external capacitor the generated Hall voltage signal is slowly adjusted via an
active high pass filter with a low cut-off frequency. This causes the output to switch into
a biased mode after a time constant is elapsed. The time constant is determined by the
external capacitor. Filtering avoids aging and temperature influence from Schmitt-trigger
input and eliminates device and magnetic offset.
The TLE 4921-3U can be exploited to detect toothed wheel rotation in a rough
environment. Jolts against the toothed wheel and ripple have no influence on the output
signal.
Furthermore, the TLE 4921-3U can be operated in a two-wire as well as in a three-wire-
configuration.
The output is logic compatible by high/low levels regarding on and off.
Circuit Description (see Figure 2)
The TLE 4921-3U is comprised of a supply voltage reference, a pair of Hall probes
spaced at 2.5 mm, differential amplifier, filter for offset compensation, Schmitt trigger,
and an open collector output.
The TLE 4921-3U was designed to have a wide range of application parameter
variations. Differential fields up to
80 mT can be detected without influence to
the switching performance. The pre-induction field can either come from a
magnetic south or north pole, whereby the field strength up to 500 mT or more will
not influence the switching points. The improved temperature compensation
enables a superior sensitivity and accuracy over the temperature range. Finally
the optimized piezo compensation and the integrated dynamic offset
compensation enable easy manufacturing and elimination of magnet offsets.
Protection is provided at the input/supply (pin 1) for overvoltage and reverse polarity and
against overstress such as load dump, etc., in accordance with ISO-TR 7637 and
DIN 40839. The output (pin 2) is protected against voltage peaks and electrical
disturbances.
Data Sheet
4
2000-07-01