IC-TW28 Datasheet, PDF (55/80 Pages) IC-Haus GmbH – 10-BIT SIN/COS INTERPOLATOR

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INPUT CONFIGURATION AND SIGNAL LEVELS
3V
Rev D2, Page 55/80
Nominal VDD (3.3 V)
The iC-TW28’s analog sin/cos inputs accept sensor sig- input properly to ensure best performance of the device.
nals with differential peak amplitudes between 20 mV Available input config^Mur^aa^xtⁱi^mon^us^ma^Inre^pus^th^Vo^ow^ltan^gi^en⁽T²a^.2b^Vle⁾ 119.
and 2.0 V in two ranges. It is important to configure the
2V
Input Range
Low
High
iC-TW28 Input Configurations
Differential Input Input
Maximum Input
Configuration MoAdmeplitude (700 mV)
Amplitude
(peak)
Loss Input Impedance Pin
Serial
Detection
1V
C3 Level MAIN_CFG.input
20 mV – 700 mV
No
Yes
65 mV – 2.0 V
Yes
>10 MΩ
220 kΩ
620 kΩ
0, 3, 6, 9
0
—
1
1, 4, 7, 10 Minimum2 Input Voltage (0.35 V)
Table 119: iC-TW28 Input C⁰onfigurations
Low input range accepts 20 – 700 mV peak amplitude
differential sin/cos signals (10 – 350 mV peak amplitude
per + or – input), as shown in Figure 27.
3V
In pin configuration mode, low input range is selected
via configuration input C3 level 0, 3, 6, or 9. In se-
rial configuration mode, low input range is selected by
2V
setting MAIN_CFG.input = 0 or 1.
Nominal VDD (3.3 V)
3V
1V
Nominal VDD
and Maximum Input
Voltage (3.3 V)
Maximum
Input
Amplitude
(2 V)
Maximum Input Voltage (2.2 V)
2V
0
Maximum Input
Amplitude (700 mV)
1V
Minimum Input Voltage (0.35 V)
0
Figure 27: Low Input Range Signals
Nominal VDD
Hig³h^V
input
range
and Maximum Input
ac_Vc_oe_lp_tat_gs_e6₍5_3.m_{3 V}V₎ – 2.0
V
peak
ampli-
tude differential sin/cos signals (32.5 mV – 1.0 V peak
amplitude per + or – input) as shown in Figure 28.
In p₂i_Vn configuration mode, high input range is selected
via configuration input C3 level 1, 4, 7, or 10. In se-
rial configuration mode, high input range is^Ms^ae^xl^imec^ut^med by
setting MAIN_CFG.input = 2.
Input
Amplitude
Hig¹h^Vinput range is implemented in the iC-⁽T²W^V)28 using
a resistive attenuator before the programmable gain
amplifier. Thus, input impedance of the sin/cos inputs
is different for the two ranges.
0
Figure 28: High Input Range Signals
The common-mode (DC) voltage of the individual sen-
sor inputs must not exceed the specified common
mode range (spec. item 103) or be such that the
peaks of the sin/cos signals exceed the maximum
input voltages shown in Figure 27 and Figure 28.
Note: 1 V_pp signals with 2.5 V common mode cannot
be connected directly to the iC-TW28 as the common
mode voltage is too high.
Sensor loss detection is accomplished by placing high
value resistors between the + and – inputs of the sin
and cos channels. In this way, floating inputs are
pulled together causing a loss of signal amplitude.
This results in a sin/cos amplitude out of range error
(STAT_VAL.scamp = 1).
Sensor outputs are typically differential, but can also be
single-ended. In this case, the SIN– and COS– inputs
must be biased to VDD/2 using an external voltage di-
vider. Do not use VC (pin 10) for this purpose as the
sensor input attenuator will draw too much current.