iC-TW8 16-BIT SIN/COS INTERPOLATOR
Pin Configuration Mode
Jan 9, 2013 Page PC10/15
For example, to configure an interpolation factor of
x80 and no auto-adaption, set C0 to configuration
level 5 (R01 = 8.06k, R02 = 6.98k) and C1 to con-
figuration level 1 (R11 = 12.1k, R12 = 3.01k). To
configure an interpolation factor of x250 and full
auto-adaption, set C0 to configuration level 5 (R01
= 8.06k, R02 = 6.98k) and C1 to configuration level
11 (R11 = 0).
Setting the Filter Mode and Hysteresis
Configuration input C2 selects the amount of filter-
ing (smoothing) and the hysteresis of the AB out-
puts of the iC-TW8. Choose the desired filter mode
and hysteresis from Table 4 and connect the appro-
priate resistors to configuration input C2 (pin 32)
according to Table 1 to set the corresponding con-
figuration level.
C2
Level
Hysteresis
(AB edges)
AB Filter Mode
11
10
9
8
7
6
5
4
3
Heavy filtering.
Smooth output at the
expense of fast
response time.
Normal filtering.
A good balance
between smoothness
and response time.
Minimal filtering.
Outputs respond
quickly to sensor
inputs (and noise).
1
2
4
8
1
2
4
8
1
2
4
8
2
1
0
Table 4: Configuration Input C2
The choice of filter mode is a compromise between
fast response, smoothness of the AB outputs, and
position lag at constant speed. It is recommended to
start with minimal filtering since this gives the fast-
est response of the AB outputs to changes in the
Sin/Cos inputs. Normal or heavy filtering may be
selected if the outputs are noisy or jittery. Experi-
mentation may be necessary to determine the opti-
mal value.
Note that configuration level C2 also sets the AB
output hysteresis in edges. The corresponding hyste-
resis in degrees of a Sin/Cos input can be calculated
using the following formula.
90
Hyster esi s []
Hysteresis [Edges]
Interpolation
Where Interpolation is the interpolation factor set
using configuration inputs C0 and C1. For example,
if Interpolation is set to x100 and hysteresis is set to
2 AB edges, the hysteresis in degrees of a Sin/Cos
input cycle is
90
Hyteresis []
2 1.8
100
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