Data Sheet
Table Of Contents
- 1 FH3D02 Overview
- 2 Characteristics
- 3 Package and Circuit Connection
- 4 SPI Communication
- 5 List of Registers
- 5.1 Measurement Register Contents
- 5.1.1 0x000B (read/write) – Measurement Control
- 5.1.2 0x000E (read/write) – Measurement Start
- 5.1.3 0x0107 (read only) – Status Register
- 5.1.4 0x0110 (read only) – Temperature Sensor
- 5.1.5 0x0111 (read only) – Bi0 Magnetic Field
- 5.1.6 0x0112 (read only) – Bi1 Magnetic Field
- 5.1.7 0x0113 (read only) – Bj0 Magnetic Field
- 5.1.8 0x0114 (read only) – Bj1 Magnetic Field
- 5.1.9 0x0120 (read only) – Magnetic Field Magnitude
- 5.1.10 0x0121 (read only) – Magnetic Field Angle
- 5.1.11 0x0122 (read only) – Linearized Angle / Bz1 Field (Special Function Mode)
- 5.1.12 0x0124 (read only) – Bz0 Magnetic Field (Special Function Mode)
- 5.2 Result Register Overview
- 5.1 Measurement Register Contents
- 6 Measurement Modes
- 6.1 Single Magnetic Probe
- 6.2 Dual Magnetic Probe
- 6.3 Linear Position or Off-Axis Angle Sensor (Absolute Field Values, Magnet On-Top)
- 6.4 Linear Position or Off-Axis Angle Sensor (Gradient Field Values, Magnet On-Top)
- 6.5 Linear Position or Off-Axis Angle Sensor (Absolute Field Values, Magnet At-The-Side)
- 6.6 Linear Position or Off-Axis Angle Sensor (Gradient Field Values, Magnet At-The-Side)
- 7 Additional Features
- 8 LZE GmbH
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Additional Features
7.7 Range Extension in Gradient Mode
In any position sensing application an angle value is calculated from two magnetic components Bi and Bj.
In rotary and absolute linear applications this angle can vary between +/-180° (see the graph below).
For linear magnet movements the magnetic fields become lower at the outside of the movement range.
The angle will be correct inside its limits until offsets and noise exceed the magnetic field amplitude.
The linearization is properly applicable.
Example data of a real magnet applied for linear position sensing as described in 6.3.1. The angle is calculated from Bi0 and Bj0
(typically pixel 0). Hence the angle is ≠0 if the magnet is placed at the centre of the IC.
In gradient mode the Bi and Bj components are calculated as differences between the register contents
(see 6.4.3 and 6.6.3). Depending on the magnet these Bi and Bj components will exhibit slightly different
shapes with additional zero-crossings in Bj. This leads to jumps between +/-180° at the zero crossings.
With these angle ambiguities a linearization is not possible.
For movements outside of these points it is possible to extend the angle range to +/-288°. Set bit
MgnRngExt in register 0x000B. See chapter 5.1.1 and 5.1.10 for further details. Only now a proper angle
linearization is applicable.
The graph below shows the output angle in gradient mode with MgnRngExt disabled and enabled.
Please note:
The internal algorithm uses absolute field values to separate angles >+180° and <-180°. Strong
external fields add up to the permanent magnet’s field and will alter the measured absolute field.
If 2*B
offset
> (Bi0 + Bi1) the calculation will give false results.
As Bi depends on the used magnet no absolute limit for magnetic offsets can be told. In the
shown example the remaining field at 10 mm displacement is ~1500 LSB or ~6 mT. Hence the
acceptable external homogeneous field may vary between +/-6 mT without angle error.
In range extension mode also the linearization table will be applied using +/-288° range. Different tables
are needed for absolute mode, gradient mode and gradient mode with range extension.
-32768
-24576
-16384
-8192
0
8192
16384
24576
32768
-10 -05 00 05 10
Value [LSB]
Position [mm]
Register values vs Position (absolute mode)
0x111 (Bi0) 0x112 (Bi1) 0x113 (Bj0) 0x114 (Bj1) 0x121 (angle)