AS5134 PB austriamicrosystems, AS5134 PB Datasheet - Page 26

• Manufacturer Part Number: AS5134 PB
• Description: BOARD PROGRAM AS5134
• Manufacturer: austriamicrosystems

Specifications of AS5134 PB

• Module/board Type: ZIF Socket
• For Use With/related Products: AS5000 Programmer, AS5134
• Lead Free Status / RoHS Status: Lead free by exemption / RoHS compliant by exemption

AS5134
Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
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. The TADC is tracking the angle of the magnet with cycle
time of 2µs (typ. 1.4). 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 255 steps (255 * 2µs = 510µs) to lock. Once it is locked, it requires only one cycle [2µs (typ. 1.4)] to track the moving
magnet. The AS5134 can operate in locked mode at rotational speeds up to min. 82.000 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:
Where:
t
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.
8.4.2 ADC Sampling Rate
For high speed applications, fast ADCs are essential. The ADC sampling rate directly influences the propagation delay. The fast tracking ADC
used in the AS5134 with a tracking rate of only 1.4 µs (typ) is a perfect fit for both high speed and high performance.
8.4.3 Chip Internal Lowpass Filtering
A commonplace practice for systems using analog-to-digital converters is to filter the input signal by an anti-aliasing filter. The filter characteristic
must be chosen carefully to balance propagation delay and noise. The lowpass filter in the AS5134 has a cutoff frequency of typ. 23.8kHz and
the overall propagation delay in the analog signal path is typ. 15.6µs.
8.4.4 Digital Readout Rate
Aside from the chip-internal propagation delay, the time required to read and process the angle data must also be considered. Due to its nature,
a PWM signal is not very usable at high speeds, as you get only one reading per PWM period. Increasing the PWM frequency may improve the
situation but causes problems for the receiving controller to resolve the PWM steps. The frequency on the AS5134 PWM output is typ. 1.33kHz
with a resolution of 2µs/step. A more suitable approach for high speed absolute angle measurement is using the serial interface. With a clock
rate of up to 6MHz, a complete set of data (21bits) can be read in >3.5µs.
8.4.5 Total Propagation Delay of the AS5134
The total propagation delay of the AS5134 is the delay in the analog signal path and the tracking rate of the ADC:
www.austriamicrosystems.com/AS5134
LOCK
= Time required to acquire the new angle after power up from one of the reduced power modes [µs]
100000000
10000000
Bit Code
11111101
11111110
---
---
t
LOCK
=
2μs ∗ NewAngle OldAngle
------------------------------------------------------------------------- -
15.6 + 1.4 = 17µs(typ)
Revision 1.13
1.406
–
Decimal Value
-128
-255
-2
-3
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(EQ 1)
(EQ 2)
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