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Features

¡¤   Advanced performance

¡¤   High sensitivity

¡¤   Symmetrical thresholds

¡¤   High piezo resistivity

¡¤   Reduced power consumption

¡¤   South and north pole pre-induction possible

¡¤   AC coupled

¡¤   Digital output signal

¡¤ Two-wire and three-wire configuration possible

¡¤   Large temperature range

¡¤   Large airgap

¡¤  Low cut-off frequency

¡¤   Protection against overvoltage

¡¤  Protection against reversed polarity

¡¤  Output protection against electrical disturbances

The differential Hall Effect sensor TLE 4921-5U provides a high sensitivity and a

superior stability over temperature and symmetrical thresholds in order to achieve a

stable duty cycle. TLE 4921-5U is particularly suitable for rotational speed detection

and timing applications of ferromagnetic toothed wheels such as anti-lock braking

systems, transmissions, crankshafts, etc. The integrated circuit (based on Hall

effect) provides a digital signal output with frequency proportional to the speed of

rotation. Unlike other rotational sensors differential Hall ICs are not influenced by

radial vibration within the effective airgap of the sensor and require no external

signal processing.

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 ageing and temperature

influence from Schmitt-trigger input and eliminates device and magnetic offset.

The TLE 4921-5U 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 4921-5U 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 4921-5U 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 4921-5U was designed to have a wide range of application parameter

variations. Differential fields up to ¡À 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 optimised 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 over-stress 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.

Contact person:

Frances New

Phone:+86-755-81832961

Fax:+86-755-83299282

Email:sumzi@sumzi.com

MSN:sumzi_frances@msn.com

http://www.sumzi.com