AS5046ASST datasheet(31/33 Pages) AMSCO

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AS5046 Programmable 360° Magnetic Angle Encoder – Preliminary Data Sheet

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In practice, there is no upper speed limit. The only restriction is

that there will be fewer samples per revolution as the speed

increases.

Regardless of the rotational speed, the absolute angular value is

always sampled at the highest resolution.

Fast Mode

(pin Mode = 1)

Slow Mode

(pin Mode = 0 or open)

610rpm = 1024 samples / turn

610rpm = 256 samples / turn

1220rpm = 512 samples / turn

1220rpm = 128 samples / turn

2441rpm = 256 samples / turn

2441rpm = 64 samples / turn

etc…

Table 10: Speed performance

18.5 Output Delays

The propagation delay is the delay between the time that

the sample is taken until it is available as angular data.

This delay is 96µs in fast mode (pin Mode = high) and

384µs in slow mode (pin Mode = low or open)

The analog output produces no further delay, the output

voltage will be updated as soon as it is available. Using

the serial interface for data transmission, an additional

delay must be considered, caused by the asynchronous

sampling (0….1/fsample) and the time it takes the external

control unit to read and process the angular data from

the AS5046.

18.5.1 Angular Error Caused by Propagation

Delay

A rotating magnet will cause an angular error caused by

the propagation delay.

This error increases linearly with speed:

delay

rpm

sampling

(deg)

∗

where

esampling = angular error [°]

rpm = rotating speed [rpm]

prop.delay = propagation delay [seconds]

Note: since the propagation delay is known, it can be

automatically compensated by the control unit processing

the data from the AS5046.

18.6 Internal Timing Tolerance

The AS5046 does not require an external ceramic

resonator or quartz. All internal clock timings for the

AS5046 are generated by an on-chip RC oscillator. This

oscillator is factory trimmed to

±5% accuracy at room

temperature (

±10% over full temperature range). This

tolerance influences the ADC sampling rate:

18.6.1 Absolute Output; Serial Interface

A new angular value is updated every

96µs +/- 5% (Mode = 1) or

384µs +/- 5% (Mode = 0 or open)

18.7 Temperature

18.7.1 Magnetic Temperature Coefficient

One of the major benefits of the AS5046 compared to

linear Hall sensors is that it is much less sensitive to

temperature. While linear Hall sensors require a

compensation of the magnet’s temperature coefficients,

the AS5046 automatically compensates for the varying

magnetic field strength over temperature. The magnet’s

temperature drift does not need to be considered, as the

AS5046 operates with magnetic field strengths from

±45…±75mT.

Example:

A NdFeB magnet has a field strength of 75mT @ –40°C and a

temperature coefficient of -0.12% per Kelvin. The temperature

change is from –40° to +125° = 165K.

The magnetic field change is: 165 x -0.12% = -19.8%, which

corresponds to 75mT at –40°C and 60mT at 125°C .

The AS5046 can compensate for this temperature related

field strength change automatically, no user adjustment

is required.

18.7.2 Accuracy over Temperature

The influence of temperature in the absolute accuracy is

very low. While the accuracy is

≤ ±0.5° at room

temperature, it may increase to

≤±0.9° due to increasing

noise at high temperatures.

18.7.3 Timing Tolerance over Temperature

The internal RC oscillator is factory trimmed to

±5%.

Over temperature, this tolerance may increase to

±10%.

Generally, the timing tolerance has no influence in the

accuracy or resolution of the system, as it is used mainly

for internal clock generation.

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