AS5134 PB austriamicrosystems, AS5134 PB Datasheet - Page 25

• Manufacturer Part Number: AS5134 PB
• Description: BOARD PROGRAM AS5134
• Manufacturer: austriamicrosystems

Specifications of AS5134 PB

• Module/board Type: ZIF Socket
• For Use With/related Products: AS5000 Programmer, AS5134
• Lead Free Status / RoHS Status: Lead free by exemption / RoHS compliant by exemption

AS5134
Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
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:
The magnetic field strength information is available in two forms:
Magnetic Field Strength Software Indicator.
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.
Factors Influencing the AGC Value.
OTP Sensitivity Adjustment.
at normal operating temperature should be in the middle between minimum and maximum, hence it should be around 100000 (20H). 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
00
8.3 Multi Turn Counter
A 9-bit register is used for counting the magnet’s revolutions. With each zero transition in any direction, the output of a special counter is
incremented or decremented. The initial value after reset is 0 LSB. The multi turn value is encoded as complement on two. Clockwise rotation
gives increasing angle values and positive turn count. Counter clockwise rotation exhibits decreasing angle values and a negative turn count
respectively.
www.austriamicrosystems.com/AS5134
H
= low sensitivity. Any value >00
- 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 initial strength of the magnet. Aging magnets may 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.
011111111
00000011
00000010
00000001
00000000
Bit Code
01111111
11111111
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To obtain best performance and tolerance against temperature or vertical distance fluctuations, the AGC value
H
will increase the sensitivity
In practical use, the AGC value will depend on several factors:
The serial data that is obtained by command READ ANGLE contains the 6-bit AGC
(see Table
Revision 1.13
3).
Decimal Value
256
127
+3
+2
+1
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-1
0
25 - 40