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AS5215

Datasheet - Detailed Descr i pti on

7 Detailed Description

The AS5215 is a redundant rotary encoder sensor front end. Based on an integrated Hall element array, the angular position of a simple two-pole

magnet is translated into analog output voltages. The angle information is provided by means of sine and cosine voltages. This approach gives

maximum flexibility in system design, as it can be directly integrated into existing architectures and optimized for various applications in terms of

speed and accuracy.

With two independent dies in one package, the device offers true redundancy. Usually the bottom die, which is exposed to slightly less magnetic

field is employed for plausibility check.

An SSI (SPI standard) protocol is implemented for internal test access to the different circuit blocks and for signal path configuration.

A One Time Programmable register block (OTP) allows the customer to adjust the signal path gain to adjust for different mechanical constraints

and magnetic field strengths. Furthermore, for internal use, the test mode can be enabled and the system oscillator is trimmable, DC offset of the

output signal can be set to either 1.5V or 2.5V. A unique chip ID is stored to ensure traceability.

For operating point control, a band gap circuit is implemented together with a central bias block to distribute all reference bias currents for the

analog signal conditioning. The digital signal part is based on a 2MHz system, CLK derived via. divider from a 4MHz system oscillator.

Figure 3. Typical Arrangement of AS5215 and Magnet

7.1 Magnet Diameter and Vertical Distance

Note:

Following is just an abstract taken from the elaborate application note on the Magnet.

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Application Notes

7.1.1 The Linear Range

The Hall elements used in the AS5000-series sensor ICs are sensitive to the magnetic field component Bz, which is the magnetic field vertical to

the chip surface. Figure 4 shows a 3-dimensional graph of the Bz field across the surface of a 6mm diameter, cylindrical NdFeB N35H magnet at

an axial distance of 1mm between magnet and IC.

The highest magnetic field occurs at the north and south poles, which are located close to the edge of the magnet, at ~2.8mm radius (see Figure

5). Following the poles towards the center of the magnet, the Bz field decreases very linearly within a radius of ~1.6mm. This linear range is the

operating range of the magnet with respect to the Hall sensor array on the chip. For best performance, the Hall elements should always be within

this linear range.