ams (formerly austriamicrosystems) has launched the AS5132, a magnetic rotary position sensor IC offering accurate angular measurement even at very high rotation speeds.
The device is a system-on-chip combining integrated Hall elements, an analog front end and digital signal processing. It is particularly well suited to industrial and automotive brushless DC (BLDC) motors, where it offers designers a small, robust and easily assembled position sensing solution. It is highly resistant to interference from stray magnetic fields.
The IC improves on previous generations of magnetic encoder by dynamically compensating for angle errors attributable to propagation delay, which are most noticeable at high speeds. Error compensation is achieved through integrated pre-commutation functions. These are very easy to configure and do not require external software routines to be executed, therefore unburdening host microcontrollers or electronic control units (ECUs).
The configuration can be changed while the device is operating, in response to changes in operating conditions such as variations in rotation speed. In addition, the advanced signal processing circuitry in the AS5132 gives it an excellent propagation delay figure of <22 μs, which means that even before pre-commutation is implemented the angle error is small.
In combination, the small propagation delay and advanced pre-commutation deliver extremely accurate angle measurement even in motors rotating at speeds up to 80 000 rpm; angle measurements are accurate to within ±3° (maximum). This enables BLDC motor manufacturers to achieve high and constant levels of torque even in high-speed applications over the whole dynamic range.
Other improvements introduced in the AS5132 include:
The device features increased sensitivity to allow operation in a magnetic field input as weak as 20 mT. This enables the sensor to be paired with a cheap ferrite magnet. In includes an external clock mode to synchronise sensor and controller systems. Implementation of a 3 V interface mode (in addition to a 5 V mode) eliminates the need for a level shifter.
When paired with a simple two-pole magnet, the AS5132 provides absolute angle measurement at a resolution of 8,5 bits, or 360 positions per revolution. This measurement is available as a serial output and as a pulse width modulated (PWM) signal. An additional U,V,W output can be used for block commutation in a BLDC motor; alternatively an incremental signal (ABI) is available.
In addition to the angle information, the strength of the magnetic field is represented as a 5-bit value. The zero position can be set by software on the production line. This simplifies assembly, as the magnet does not need to be precisely aligned with a fixed starting position.
For more information contact Gary de Klerk, NuVision Electronics, +27 (0)11 608 0144, [email protected], www.nuvisionelec.co.za
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