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AS5134

Datasheet - Application In form atio n

8.2 AS5134 Status Indicators

8.2.1 Lock Status Bit

The Lock signal indicates, whether the angle information is valid (ADC locked, Lock = high) or invalid (ADC unlocked, Lock = low). To determine

a valid angular signal at best performance, the following indicators can be set:

Lock = 1

AGC = >00H and < 3FH

After a startup of the AS5134 at the initial zero position the lock status bit will remain at (Lock=0). After a mechanical rotation (1º) the lock status

bit will change to (Lock=1).

Note: The angle signal is also valid (Lock = 1), when the AGC is out of range (00H or 3FH), but the accuracy of the AS5134 is reduced due to

the out of range condition of the magnetic field strength.

8.2.2 Magnetic Field Strength Indicators

The AS5134 is not only able to sense the angle of a rotating magnet, it can also measure the magnetic field strength (and hence the vertical

distance) of the magnet. This additional feature can be used for several purposes:

- as a safety feature by constantly monitoring the presence and proper vertical distance of the magnet

- as a state-of-health indicator, e.g. for a power-up self test

- as a pushbutton feature for rotate-and-push types of manual input devices

The magnetic field strength information is available in two forms:

information. The AGC is an automatic gain control that adjusts the internal signal amplitude obtained from the Hall elements to a constant level.

If the magnetic field is weak, e.g. with a large vertical gap between magnet and IC, with a weak magnet or at elevated temperatures of the

magnet, the AGC value will be high. Likewise, the AGC value will be lower when the magnet is closer to the IC, when strong magnets are used

and at low temperatures.

The best performance of the AS5134 will be achieved when operating within the AGC range. It will still be operational outside the AGC range, but

with reduced performance especially with a weak magnetic field due to increased noise.



The initial strength of the magnet. Aging magnets show a reducing magnetic field over time which results in an increase of the AGC

value. The effect of this phenomenon is relatively small and can easily be compensated by the AGC.



The vertical distance of the magnet. Depending on the mechanical setup and assembly tolerances, there will always be some variation of

the vertical distance between magnet and IC over the lifetime of the application using the AS5134. Again, vertical distance variations can be

compensated by the AGC.



The temperature and material of the magnet. The recommended magnet for the AS5134 is a diametrically magnetized, 5-6mm diameter

NdFeB (Neodymium-Iron-Boron) magnet. Other magnets may also be used as long as they can maintain to operate the AS5134 within the

AGC range. Every magnet has a temperature dependence of the magnetic field strength. The temperature coefficient of a magnet depends

on the used material. At elevated temperatures, the magnetic field strength of a magnet is reduced, resulting in an increase of the AGC

value. At low temperatures, the magnetic field strength is increased, resulting in a decrease of the AGC value. The variation of magnetic

field strength over temperature is automatically compensated by the AGC.

at normal operating temperature is in the middle between minimum and maximum, hence it is around 100000 bin (20hex). To facilitate the

“vertical centering” of the magnet+IC assembly, the sensitivity of the AS5134 can be adjusted in the OTP register in 4 steps. A sensitivity

adjustment is recommended, when the AGC value at normal operation is close to its lower limit (around 00H). The default sensitivity setting is