AS5261

Datasheet - Detailed Descr i p ti on

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8 Detailed Description

The AS5261 is manufactured in a CMOS process and uses a spinning current Hall technology for sensing the magnetic field distribution across

the surface of the chip. This IC consists of two galvanic isolated dies. All following in and register names refers to one die.

The integrated Hall elements are placed around the center of the device and deliver a voltage representation of the magnetic field at the surface

of the IC.

Through Sigma-Delta Analog / Digital Conversion and Digital Signal-Processing (DSP) algorithms, the AS5261 provides accurate high-resolution

absolute angular position information. For this purpose a Coordinate Rotation Digital Computer (CORDIC) calculates the angle and the

magnitude of the Hall array signals.

The DSP is also used to provide digital information at the outputs that indicate movements of the used magnet towards or away from the device’s

surface.

A small low cost diametrically magnetized (two-pole) standard magnet provides the angular position information.

The AS5261 senses the orientation of the magnetic field and calculates a 14-bit binary code. This code is mapped to a programmable output

characteristic in a PWM duty cycle format. This signal is available at the pin (OUT).

The application angular region can be programmed in a user friendly way. The start angle position T1 and the end point T2 can be set and

programmed according the mechanical range of the application with a resolution of 14 bits. In addition the T1Y and T2Y parameter can be set

and programmed according the application. The transition point 0 to 360 degree can be shifted using the break point parameter BP. The voltage

for clamping level low CLL and clamping level high CLH can be programmed with a resolution of 9 bits. Both levels are individually adjustable.

Two additional linearization points can be used to improve the system linearity. These points C1 and C2 are programmable.

The output parameters can be programmed in an OTP register. No additional voltage is required to program the AS5261. The setting may be

overwritten at any time and will be reset to default when power is cycled. To make the setting permanent, the OTP register must be programmed

by using a lock bit the content could be frozen for ever.

The AS5261 is tolerant to magnet misalignment and unwanted external magnetic fields due to differential measurement technique and Hall

sensor conditioning circuitry.

8.1 Operation

8.1.1 VDD Voltage Monitor

detection time the output is turned off. When the over voltage event has passed and the voltage applied to the VDD pin falls below the over-

voltage lower threshold for longer than the recovery time the device enters the normal mode and the output is enabled.

the detection time the output is turned off. When the voltage applied to the VDD pin exceeds the under-voltage upper threshold for longer than

the detection time the device enters the normal mode and the output is enabled.

8.2 PWM Output

By default (after programmed CUST_LOCK OTP bit) the PWM output mode is selected. The pin OUT provides a modulated signal that is

proportional to the angle of the rotating magnet. Due to an intelligent approach a permanent short circuit will not damage the device. This is also

feasible in a high voltage condition up to 20 V and at the highest specified ambient temperature.

After the digital signal processing (DSP) a PWM engine provides the output signal.

The DSP maps the application range to the output characteristic. An inversion of the slope is also programmable to allow inversion of the rotation

direction.

An on-chip diagnostic feature handles the error state at the output. Depending on the failure the output is in HiZ condition or indicates a PWM

signal within the failure bands of 4 – 96 % duty cycle. (see Table 8)