IC-TW28 Datasheet, PDF (24/80 Pages) IC-Haus GmbH – 10-BIT SIN/COS INTERPOLATOR

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Rev D2, Page 24/80
CONFIGURATION OVERVIEW
The iC-TW28 can be configured for a specific applica-
tion in one of three ways. For simple, stand-alone ap-
plications, a pin configuration interface is available. Pin
configuration mode provides easy selection of the most
common interpolation factors and operating modes.
Choose the desired interpolation factor from Table 8
and connect the appropriate resistors to configuration
input C0 according to Table 7 to set the corresponding
configuration level.
For access to all iC-TW28 features in more sophisti-
cated stand-alone or hosted applications, serial config-
uration mode must be used. Serial configuration can be
done through the SPI port or the Encoder Link interface,
which uses the A+ and A- outputs for communication.
The Encoder Link interface can be used in hosted ap-
plications to provide factory configuration independent
of the host processor or for field re-configuration.
Pin Configuration Mode
Pin configuration mode is recommended for
stand-alone applications since it does not require any
programming and is simple and easy to implement
for fixed configurations in production. To select pin
configuration mode, connect the PINCFG pin to 3.3 V
and connect eight resistors to the four configuration
inputs as shown in Configuration Resistors on page 23.
The recommended resistor values for setting the con-
figuration levels are shown in Table 7.
C0
Level
11
10
9
8
7
6
5
4
3
2
1
0
Interpolation
Group I0
256
128
64
32
16
12
8
6
4
3
2
1
Interpolation
Group I1
250
200
180
125
100
80
50
40
25
20
10
5
Table 8: Configuration Input C0
Note: The interpolation factors shown in Table 8 are
the number or AB output cycles per sin/cos input cy-
cle. There are four times as many AB output edges
per sin/cos input cycle than shown in the table.
Configuration Nominal
Rx1
Rx2
Level
Voltage
kΩ
kΩ
11
3.30
0.00
∞
10
3.00
10.0
100
9
2.70
11.5
51.1
8
2.40
11.5
30.1
7
2.10
16.2
28.7
6
1.80
9.53
11.5
5
1.50
11.5
9.53
4
1.20
28.7
16.2
3
0.90
30.1
11.5
2
0.60
51.1
11.5
1
0.30
100
10.0
0
0.00
∞
0.00
Table 7: Pin Configuration Resistor Values
EIA E48 series 2% resistors or E96 series 1% resis-
tors are recommended to guarantee reliable operation
under all conditions. An open circuit is shown as infi-
nite (∞) resistance and a short circuit is shown as zero
resistance in Table 7.
Hysteresis and Filtering
Configuration input C1 selects the hysteresis and the
amount of filtering (smoothing) of the AB outputs of the
iC-TW28. Choose the desired hysteresis and amount
of filtering from Table 9 and connect the appropriate
resistors to configuration input C1 according to Table 7
to set the corresponding configuration level.
C1
Level
11
10
9
8
7
6
5
4
3
2
1
0
Hysteresis
±2.8^◦
±1.4^◦
±0.7^◦
±0.35^◦
±2.8^◦
±1.4^◦
±0.7^◦
±0.35^◦
±2.8^◦
±1.4^◦
±0.7^◦
±0.35^◦
AB Filtering
Heavy filtering
Medium filtering
Light filtering
Interpolation Factor
Configuration inputs C0 and C3 are used to select the
interpolation factor. Input C3 selects the desired in-
terpolation group I0 or I1 and input C0 selects the de-
sired interpolation factor from within the selected group.
Table 9: Configuration Input C1
The hysteresis level is shown in degrees of a sin/cos
input cycle.