www.austriamicrosystems.com/AS5134

Revision 2.3

25 - 32

AS5134

Datasheet - Application In form atio n

8.3 Multi Turn Counter

A 9-bit register is used for counting the magnet’s revolutions. With each zero transition in any direction, the output of a special counter is

incremented or decremented. The initial value after reset is 0 LSB. The multi turn value is encoded as complement on two. Clockwise rotation

gives increasing angle values and positive turn count. Counter clockwise rotation exhibits decreasing angle values and a negative turn count

respectively.

The counter output can be reset by using command 20 – SET MT Counter. It is immediately reset by the rising clock edge of this bit. Any zero

crossing between the clock edge and the next counter readout changes the counter value.

8.4 High Speed Operation

The AS5134 is using a fast tracking ADC (TADC) to determine the angle of the magnet. Once the TADC is synchronized with the angle, it sets

the LOCK bit in the status register. In worst case, usually at start-up, the TADC requires up to 179 steps to lock. Once it is locked, it requires only

one cycle to track the moving magnet. The AS5134 can operate in locked mode at rotational speeds up to 76875 rpm.

In Low Power Mode, the position of the TADC is frozen. It will continue from the frozen position once it is powered up again. If the magnet has

moved during the power down phase, several cycles will be required before the TADC is locked again. The tracking time to lock in with the new

magnet angle can be roughly calculated as:

(EQ 1)

Where:

OldAngle = Angle position when one of the reduced power modes is activated [º]

NewAngle = Angle position after resuming from reduced power mode [º]

8.4.1 Propagation Delay

The Propagation delay is the time required from reading the magnetic field by the Hall sensors to calculating the angle and making it available on

the serial or PWM interface. While the propagation delay is usually negligible on low speeds, it is an important parameter at high speeds. The

longer the propagation delay, the larger becomes the angle error for a rotating magnet as the magnet is moving while the angle is calculated. The

position error increases linearly with speed. The main factors that contribute to the propagation delay are discussed in detail further in this

document.

Bit Code

Decimal Value

011111111

256

---

---

01111111

127

---

---

00000011

+3

00000010

+2

00000001

+1

00000000

0

11111111

-1

11111110

-2

11111101

-3

---

---

10000000

-128

---

---

100000000

-255

2

s NewAngle OldAngle

–

1.406

--------------------------------------------------------------------------

=