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## AS5304 Datasheet(PDF) 9 Page - ams AG

 Part No. AS5304 Description Integrated Hall ICs for Linear and Off-Axis Rotary Motion Detection Download 13 Pages Scroll/Zoom 100% Maker AMSCO [ams AG] Homepage http://www.ams.com Logo ## AS5304 Datasheet(HTML) 9 Page - ams AG

 9 / 13 page AS5304/AS5306 Integrated Hall IC for linear and off-axis rotary motion detectionRevision 1.5www.austriamicrosystems.comPage 9 of 138.1Resolution and Maximum Rotating SpeedWhen using the AS5304/AS5306 in an off-axis rotary application, a multi-pole ring magnet must be used. Resolution, diameterand maximum speed depend on the number of pole pairs on the ring.8.1.1ResolutionThe angular resolution increases linearly with the number of pole pairs. One pole pair has a resolution (= interpolation factor) of160 steps or 40 quadrature pulses.Resolution [steps] = [interpolation factor] x [number of pole pairs]Resolution [bit] = log (resolution[steps]) / log (2)Example: multi-pole ring with 22 pole pairsResolution= 160x22 = 3520 steps per revolution= 40x22 = 880 quadrature pulses / revolution= 11.78 bits per revolution = 0.1023° per step8.1.2Multi-pole Ring DiameterThe length of a pole pair across the median of the multi-pole ring must remain fixed at either 4mm (AS5304) or 2.4mm(AS5306). Hence, with increasing pole pair count, the diameter increases linearly with the number of pole pairs on the magneticring.Magnetic ring diameter = [pole length] * [number of pole pairs] / πfor AS5304: d = 4.0mm * number of pole pairs / πfor AS5306: d = 2.4mm * number of pole pairs / πExample: same as above: multi-pole ring with 22 pole pairs for AS5304Ring diameter =4 * 22 / 3.14 = 28.01mm (this number represents the median diameter of the ring, this is where theHall elements of the AS5304/AS5306 should be placed; see Figure 4)For the AS5306, the same ring would have a diameter of: 2.4 * 22 / 3.14 = 16.8mm8.1.3Maximum Rotation SpeedThe AS5304/AS5306 use a fast interpolation technique allowing an input frequency of 5kHz. This means, it can processmagnetic field changes in the order of 5000 pole pairs per second or 300,000 revolutions per minute. However, since a magneticring consists of more than one pole pair, the above figure must be divided by the number of pole pairs to get the maximumrotation speed:Maximum rotation speed = 300,000 rpm / [number of pole pairs]Example: same as above: multi-pole ring with 22 pole pairs:Max. speed = 300,000 / 22 = 13,636 rpm (this is independent of the pole length)8.1.4Maximum Linear Travelling SpeedFor linear motion sensing, a multi-pole strip using equally spaced north and south poles is used. The pole length is again fixedat 2.0mm for the AS5304 and 1.2mm for the AS5306. As shown in 8.1.3 above, the sensors can process up to 5000 pole pairsper second, so the maximum travelling speed is:Maximum linear travelling speed = 5000 * [pole pair length]Example: linear multi-pole strip:Max. linear travelling speed = 4mm * 5000 1/sec = 20,000mm/sec = 20m/secfor AS5304Max. linear travelling speed = 2.4mm * 5000 1/sec = 12,000mm/sec = 12m/secfor AS5306

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