Application Note TLE49x5

Silicon Hall ICs
Application Notes: Uni- and Bipolar Hall IC Switches
Detection of rotational speed
Detection of linear position and rotational position
Non contact limit switch
Flow-rate measurement
Brushless commutation
Main Features
For uni- and bipolar fields
Clean, rapid and bounce-free switching
No mechanical wear
Low power consumption
Insensitive to contamination
Wide temperature range
Reverse polarity protection
General Description
The integrated Uni- and Bipolar Hall IC switch series TLE 49x5 is designed specifically
for industrial, automotive and consumer applications. These magnetic sensors with
digital output are available as unipolar and bipolar switches and bipolar latches.
The bipolar circuit includes the Hall element, an operational transconduction amplifier
and a Schmitt-Trigger. Compensation electronics guarantees a linear temperature
behaviour of the switching thresholds with a negative slope. A quadruple Hall cell
arrangement minimizes the piezoresistive effect (sensitivity to mechanical stresses).
The open-collector output can sink up to 100 mA.
Design and Function of the Chip
A magnetic field acting perpendiculary to the chip surface generates a voltage on the
probe terminals of the Hall element. This voltage is amplified and fed into a SchmittTrigger that drives an npn-transistor, the collector of which gives the output. If the
induction exceeds the turn-on induction, the output transistor will conduct. If the
magnetic field is reduced by the hysteresis, the output ceases to conduct.
To minimize the variation of the switching points as a result of supply voltage drift and
ambient temperature, the Hall probe is fed from a stabilized voltage source. The
switching thresholds are stabilized in the operating temperature range by a
compensation circuit.
The devices are protected internally against reverse polarity protection.
Data Book
Silicon Hall ICs
The TLE 4905 L is a unipolar switch, i.e. it only reacts to a magnetic south pole.
Hereafter the flux caused by a magnetic south (north) pole is defined as a positive
(negative) flux. If an applied positive magnetic flux density exceeds the turn-on value
BOP, the output conducts. If the magnetic flux density falls below the positive turn-off
value BRP, the output is inhibited again. The typical application is that of a position switch
actuated by the proximity of a permanent magnet.
The TLE 4935/35-2/45 are bipolar switches. They switch into a conducting state when
the positive flux density BOP is exceeded and they do not switch back to the inhibited state
until the equally strong negative flux density BRP is applied. In the absence of a field the
output retains in the last state (latch). Bipolar switches are applied for electronic
commutation of brushless DC motors, position detection and speed measurement of a
rotating magnetic bar or magnetic encoder wheel.
Figure 55
Block Diagram of Uni- and Bipolar Hall IC Switches
The following sections present the test results of the DIN 40839-1 and -4 tests and show
how the Hall IC switches are to be used in equipment guaranteeing Electromagnetic
Injection of Supply Line Transients (DIN 40839-1)
Internally the devices TLE 4905/35/35-2/45/45-2 have no protection against surge
voltages, only against reversal of the supply voltage, so the supply voltage limit
− 40 V < VS ≤ 32 V must not be exceeded under any circumstances.
Data Book
Silicon Hall ICs
Stage 1: Without External Protection
If the devices are operated in the application circuit according to the data sheet, the high
pulse amplitudes (with the exception of pulses 1 and 4) exceed the limit of the supply
voltage. Without a protection circuit there will naturally be failures.
Figure 56
TLE 4905/35/35-2/45/45-2 without External Protection
Data Book
Silicon Hall ICs
Stage 2: Simple Surge Protection
In this case a simple zener diode (or also a suppressor diode) is used for surge
Figure 57
TLE 4905/35/35-2/45/45-2 with Simple Surge Protection
Data Book
Silicon Hall ICs
Stage 3: Complete Protection
The illustrated protective circuitry is effective against all standard interference pulses of
severity level IV. The lower limit of the supply voltage for the circuit is slightly higher
(approx. 1 V) than that of the devices.
Figure 58
TLE 4905/35/35-2/45/45-2 with Complete Protective Circuitry
Data Book
Silicon Hall ICs
Radiated Interference (DIN 40839-4)
The device in the application circuit according to Figure 56 is exposed to an
electromagnetic field in the range from 100 kHz to 750 kHz with field strength of
100 V/m with 1 kHz AM
200 V/m without AM
in a TEM cell. The tested item is located at the end of a 20 cm long, open adapter board
in the center of the cell.
Figure 59
Test Setup with TEM Cell
No switching error occurs, the previously set Low or High states are maintained. The
same applies for the minimum operating voltage.
Data Book