AS5050A datasheet(10/31 Pages) AMSCO

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[v2-06] 2014-Oct-14

AS5050A − Detailed Description

Power Supply Filter

Due to the sequential internal sampling of the Hall sensors,

fluctuations on the analog power supply (pin#12: VDD) may

cause additional jitter of the measured angle. This jitter can be

avoided by providing a stable VDD supply.

The easiest way to achieve that is to add a RC filter: 15

Ω in series

and 4.7μF to ground as shown in Figure 10.

Alternatively, a filter: 33

Ω + 2.2μF may be used. However with

this configuration, the minimum supply voltage is 3.15V.

Reading an Angle

Sending a READ ANGLE command through the SPI interface

automatically powers up the chip, drives INT/ high and starts

another angle measurement. The completion of the angle

measurement is indicated by driving the INT/ output low and

clearing the WOW flag in the error status register. The

microcontroller can respond to the interrupt by reading the

angle value from the AS5050A over the SPI interface. (See

Figure 11).

A READ ANGLE command must not be sent while a

measurement is being performed as indicated by INT/ driven

high or WOW = 1.

Reducing the Angle Jitter

The chip only performs a single angle measurement after a

READ ANGLE command is received, after which it returns to

low-power mode, so it is in normal operating mode for only a

very short time (tPwrUp).

The angle jitter can be reduced by averaging several angle

measurements in the microcontroller. For example, an

averaging of four samples reduces the jitter by 6dB (50%).

Operating Modes

After a READ ANGLE command is sent, the angle is measured

and internal calculations are started. During this time (normal

operating mode) the INT/ output is high until the device finishes

the calculations and a second READ ANGLE command may not

be sent.

After the INT/ output is driven low the device goes into

low-power mode. If the microcontroller doesn't monitor the

INT/ output a minimum guard time (treadout) must be inserted

before the next READ ANGLE command can be sent.

After startup the AS5050A has higher power consumption than

during low-power mode. When the POR cell is deactivated the

chip uses less current during low-power mode (see POR OFF

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