AS5245-HQFT-500 austriamicrosystems, AS5245-HQFT-500 Datasheet - Page 26

• Manufacturer Part Number: AS5245-HQFT-500
• Description: IC ENCODER ROTARY 32-QFN
• Manufacturer: austriamicrosystems
• Type: Linear, Rotary Encoder - Programmabler

Specifications of AS5245-HQFT-500

• Featured Product: AS5245 – Dual Die Motion Sensing IC
• Sensing Range: 45mT ~ 75mT
• Voltage - Supply: 3 V ~ 3.6 V, 4.5 V ~ 5.5 V
• Current - Supply: 21mA
• Current - Output (max): 4mA
• Output Type: Quadrature with Index (Incremental)
• Features: Programmable
• Operating Temperature: -40°C ~ 150°C
• Package / Case: 32-VQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: AS5245-HQFT-500TR

AS5245
Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
Incremental Mode.
AS5245 has a built-in interpolator, which ensures that there are no missing pulses at the incremental outputs for rotational speeds of up to
30.000 rpm, even at the highest resolution of 10 bits (512 pulses per revolution).
9.6.4 Propagation Delays
The propagation delay is the delay between the time that the sample is taken until it is converted and available as angular data. This delay is
96µs in fast mode and 384µs in slow mode.
Using the SSI interface for absolute 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 chip (maximum clock rate = 1MHz, number
of bits per reading = 18).
Angular Error Caused by Propagation Delay.
This error increases linearly with speed:
Where:
esampling = angular error [º]
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 AS5245.
9.6.5 Internal Timing Tolerance
The AS5245 does not require an external ceramic resonator or quartz. All internal clock timings for the AS5245 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:
9.6.6 Temperature
Magnetic Temperature Coefficient.
sensitive to temperature. While linear Hall sensors require a compensation of the magnet’s temperature coefficients, the AS5245 automatically
compensates for the varying magnetic field strength over temperature. The magnet’s temperature drift does not need to be considered, as the
AS5245 operates with magnetic field strengths from ±45…±75mT.
Example:
A NdFeB magnet has a field strength of 75mT @ -40ºC and a temperature coefficient of -0.12% per Kelvin. The temperature change is from -40º
to +125º = 165K.The magnetic field change is: 165 x -0.12% = -19.8%, which corresponds to 75mT at -40ºC and 60mT at 125ºC.
The AS5245 can compensate for this temperature related field strength change automatically, no user adjustment is required.
9.6.7 Accuracy over Temperature
The influence of temperature in the absolute accuracy is very low. While the accuracy is less than or equal to ±0.5º at room temperature, it may
increase to less then or equal to ±0.9º due to increasing noise at high temperatures.
www.austriamicrosystems.com/AS5245
Absolute Output; SSI Interface: A new angular value is updated every 96µs (typ) in fast mode and every 384µs (typ) in slow mode.
PWM Output: A new angular value is updated every 400µs (typ). The PWM pulse timings t
the internal oscillator. If only the PWM pulse width t
However, this tolerance can be cancelled by measuring both t
Modulation (PWM) Output on page
Incremental Mode: In incremental mode, the transition noise influences the period, width and phase shift of the output signals A, B and
Index. However, the algorithm used to generate the incremental outputs guarantees no missing or additional pulses even at high speeds (up
to 30.000 rpm and higher).
Incremental encoders are usually required to produce no missing pulses up to several thousand rpms. Therefore, the
15).
One of the major benefits of the AS5245 compared to linear Hall sensors is that it is much less
A rotating magnet will cause an angular error caused by the output propagation delay.
Position =
ON
e
sampling
is used to measure the angle, the resulting value also has this timing tolerance.
= rpm * 6 * prop.delay
------------------------ - 1
(
t
ON
t
on
on
Revision 1.5
⋅
and t
+
4097
t
off
OFF
)
–
and calculating the angle from the duty cycle
ON
and t
OFF
also have the same tolerance as
(see Pulse Width
(EQ 5)
(EQ 6)
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