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AS5140H

Data Sheet - D e t a i l e d D e s c r i p t i o n

In absolute mode (serial interface and PWM output), 610 rpm is the maximum speed, where 1024 readings per revolution can be obtained. In

incremental mode, the maximum error caused by the sampling rate of the ADCs is 0/+96µs. It has a peak of 1LSB = 0.35º at 610 rpm. At higher

speeds, this error is reduced again due to interpolation and the output delay remains at 192µs as the DSP requires two sampling periods

(2x96µs) to synthesize and redistribute any missing pulses.

AS5140H has a built-in interpolator, which ensures that there are no missing pulses at the incremental outputs for rotational speeds of up to

10.000 rpm, even at the highest resolution of 10 bits (512 pulses per revolution).

7.12.4 Propagation Delays

The propagation delay is the delay between the time that a sample is taken until it is converted and available as angular data. This delay is 48µs

for the absolute interface and 192µs for the incremental interface. Using the SSI interface for absolute data transmission, an additional delay

must be considered, caused by the asynchronous sampling (t=0…1/fs) and the time it takes the external control unit to read and process the

data.

error increases linearly with speed:

(EQ 8)

Where:

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 that is processing the data from the

AS5140H, thus reducing the angular error caused by speed.

7.12.5 Internal Timing Tolerance

The AS5140H does not require an external ceramic resonator or quartz. All internal clock timings for the AS5140H 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 and the pulse width of the PWM output:

Absolute output; SSI interface: A new angular value is updated every 100µs (typ.)

Incremental outputs: The incremental outputs are updated every 100µs (typ.)

(PWM) Output on page 16):

Position =

(EQ 9)

Table 21. Speed Performance

Absolute Output Mode

Incremental Output Mode

610rpm = 1024 samples / turn

No missing pulses

@ 10 bit resolution (512ppr):

max. speed = 10.000 rpm

122rpm = 512 samples / turn

2441rpm = 256 samples / turn

etc.

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