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AS5040 View Datasheet(PDF) - Unspecified

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AS5040 Datasheet PDF : 20 Pages
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AS5040 10-BIT PROGRAMMABLE MAGNETIC ROTARY ENCODER
Single Channel Output (LSB / Dir Mode)
Output LSB reflects the LSB (least significant bit) of the
actual programmed incremental resolution (OTP Register Bit
Div0, Div1). Output Dir provides information about the
rotational direction of the magnet, which may be placed
above or below the device (1=clockwise; 0=counter
clockwise; top view). Dir is updated with every LSB change.
In both modes (quad A/B, single channel) the resolution and
the index output are user programmable. The index pulse
indicates the zero position and is by default one angular
step (1LSB) wide. However, it can be set to three LSBs by
programming the Index-bit of the OTP-Register accordingly
(see Table 7).
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.
Incremental mode:
Incremental encoders are usually required to produce
NO missing pulses up to several thousand rpm’s.
Therefore, the AS5040 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 10bits (256 pulses per revolution).
High Speed Operation
Absolute mode:
The AS5040 has an internal sampling rate of 10kHz.
Consequently, it will sample the angle of the magnet every
100µs. Given this value, for a magnet rotating at high
speed, the number of samples (n) per turn can be
calculated by
n
=
rpm
60
100µs
Absolute Output Mode
Incremental Output
Mode
586 rpm = 1024 samples / turn
1172 rpm = 512 samples / turn
2343 rpm = 256 samples / turn
etc…
no missing pulses
@ 10bit resolution (256ppr):
max. speed = 10,000 rpm
Table 6: Speed performance
Quad A/B-Mode
A
B
Index
LSB / Dir-Mode
LSB
Dir
CSn
t Incremental outputs valid
Revision 1.1
mechanical
zero position
Rotation Direction
Change
mechanical
zero position
Index=0
1LSB
Index=1
3 LSB
Hyst =
2 LSB
clockwise cw
counterclockwise ccw
t Dir valid
Figure 6: Incremental Output Modes
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