AS5140H-ASSU austriamicrosystems, AS5140H-ASSU Datasheet - Page 32

• Manufacturer Part Number: AS5140H-ASSU
• Description: ENCODER, MAGNETIC, ROTARY, 10BIT, 16SSOP
• Manufacturer: austriamicrosystems

Specifications of AS5140H-ASSU

• Brief Features: User Programmable Zero / Index Position, Failure Detection Mode
• Supply Voltage Range: 3V To 3.6V, 4.5V To 5.5V
• Operating Temperature Range: -40°C To +150°C
• Digital Ic Case: RoHS Compliant
• Ic Function: 10-bit Programmable Magnetic Rotary Encoder
• Rohs Compliant: Yes

AS5140H
Data Sheet - D e t a i l e d D e s c r i p t i o n
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 of 10 bit. Likewise, for a given number of samples per revolution (n), the maximum speed can be calculated
by:
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.
Incremental Mode
Incremental encoders are usually required to produce no missing pulses up to several thousand rpm. Therefore, the
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).
Table 11. Speed Performance
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.
Angular Error Caused by Propagation Delay
A rotating magnet will therefore cause an angular error caused by the output delay. This error increases linearly with
speed:
Where:
e
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
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:
www.austriamicrosystems.com
sampling
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: A new angular value is updated every 100µs (typ.). The PWM pulse timings T
the same tolerance as the internal oscillator. If only the PWM pulse width T
processing the data from the AS5140H, thus reducing the angular error caused by speed.
= angular error [º]
610rpm = 1024 samples / turn
2441rpm = 256 samples / turn
122rpm = 512 samples / turn
Absolute Output Mode
etc.
e
sampling
rpm =
= rpm * 6 * prop.delay
Revision 1.1
------------------- -
n 96μs
⋅
60
@ 10 bit resolution (512ppr):
Incremental Output Mode
max. speed = 10,000 rpm
on
No missing pulses
is used to measure the angle, the
on
and T
off
also have
32 - 38
(EQ 7)
(EQ 8)