iC-TW8 16-BIT SIN/COS INTERPOLATOR
Pin Configuration Mode
Jan 9, 2013 Page PC9/15
Setting the Interpolation Factor
Setting the Auto-Adaption Mode
Configuration inputs C0 and C1 are used to select
the interpolation factor. Input C1 selects the desired
interpolation group I0, I1, or I2 and input C0 selects
the desired interpolation factor from within the se-
lected group. Choose the desired interpolation factor
from Table 2 and connect the appropriate resistors
to configuration input C0 (pin 30) according to Ta-
ble 1 to set the corresponding configuration level.
Configuration input C1 is used to select the desired
auto-adaption mode and the interpolation group cor-
responding to the interpolation factor selected via
configuration input C0. Choose the desired auto-
adaption mode and interpolation group from Table 3
and connect the appropriate resistors to configura-
tion input C1 (pin 31) according to Table 1 to set the
corresponding configuration level.
C0
Level
11
10
9
8
7
6
5
4
3
2
1
Interp.
Interp.
Interp.
C1
Level
11
10
9
8
7
6
5
4
3
2
1
Auto-Adaption
Mode
A3: Full analog
and digital auto-
adaption.
Interpolation
Group I0 Group I1 Group I2
Group
I2
x81921
x40962
x2048
x1024
x512
x256
x128
x64
x1600
x800
x400
x200
x160
x100
x80
x100001
x50002
x2500
x1250
x1000
x500
I1
I0
I2
I1
I0
I2
I1
I0
A2: Full digital
auto-adaption.
x250
A1: Digital offset
and gain auto-
adaption.
x50
x40
x20
x10
x125
x32
x16
x8
x4
x62.53
x25
I2
I1
I0
x12.53
x6.253
A0: No auto-
adaption.
0
x5
0
Table 2: Configuration Input C0
Table 3: Configuration Input C1
The interpolation factors shown in Table 2 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 as shown in the table.
Three auto-adaption modes are available in pin con-
figuration mode. Mode A3 provides full analog and
digital auto-adaption. In this mode, the iC-TW8
continuously adjusts analog gain, analog offset,
digital offset, digital gain, and digital phase during
operation to maintain optimum performance and
lowest error and jitter.
Note that while the iC-TW8 is a true 16-bit interpo-
lator, x10000 is the maximum interpolation factor
available in pin configuration mode. Full 16-bit
(x16384) interpolation is available in serial configu-
ration mode.
Auto-adaption mode A2 provides full digital auto-
adaption and is the recommended mode for most
applications. In this mode, analog gain and offset
are fixed at the values established during device cal-
ibration (see Auto Calibration on page 12) and the
iC-TW8 continuously adjusts only the digital offset,
digital gain match, and digital phase during opera-
tion to maintain optimum performance and lowest
error and jitter.
1 This interpolation factor can only be used with heavy
filtering (C2 configuration levels 8–11) and lag
recovery enabled (C3 configuration levels 6–11).
Auto-adaption mode A1 is similar to mode A2 ex-
cept that digital phase is fixed at the value estab-
lished during device calibration and not adjusted
during operation.
2 This interpolation factor can only be used with normal
or heavy filtering (C2 configuration levels 4–11) and
lag recovery enabled (C3 configuration levels 6–11).
3
In mode A0, auto-adaption is disabled and parame-
ter values are not adjusted from their initial calibra-
tion values during operation.
Z output is not synchronous with AB outputs when
using fractional interpolation factors.
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