IC-TW28 Datasheet, PDF (20/80 Pages) IC-Haus GmbH – 10-BIT SIN/COS INTERPOLATOR

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Rev D2, Page 20/80
The basic electrical connections for a hosted applica-
tion using a single iC-TW28 are shown in Figure 12.
Multiple iC-TW28s can also be bussed or chained to-
gether using the same SPI port on the host processor
or microcontroller. See Bussing Multiple iC-TW28s on
page 75 and Chaining Multiple iC-TW28s on page 76
for more information.
3.3V
PINCFG tied low for
SPI Configuration mode
1µF
iC-TW28
3.3V
DVDD
PINCFG
DVSS
IOVDD
IOVSS
1µF
3.3V
A+
A–
AVDD
B+
B–
1µF
AVSS
Z+
Z–
SIN+
Sensor
SIN–
COS+
COS–
ZERO+
3.3V
ZERO–
100
nF
xCALIB
RESERVED
RESERVED
RESERVED
VREF
VC
100
nF
xRST
xIRQ
xSS/C0
SCLK/C1
SI/C2
SO/C3
120 Ω
Differential
120 Ω
RS422
ABZ Outputs
120 Ω
Host µP
OUTx
IRQx
xCS
SCLK
MO
MI
Figure 12: Typical Electrical Connections For Hosted Application
Power and Ground
The iC-TW28 requires a high quality ground and
clean 3.3 V power supplies. There are three sepa-
rate power/ground pin pairs, one each for the analog
(AVDD/AVSS), digital (DVDD/DVSS), and I/O (IOVD-
D/IOVSS) circuitry.
xCALIB Input
The active-low xCALIB input is used to activate the au-
to-calibration feature of the iC-TW28. A push-button
and pull-up resistor can be connected to this input as
shown for easy manual calibration. xCALIB can also be
controlled by a host processor or microcontroller output,
if desired.
In most cases, it is sufficient to connect all three power
pins to the same low-impedance power source, prefer-
ably an on-board voltage regulator. Likewise, the three
ground pins can usually be connected to the same solid
ground plane on the PC board. If necessary, separate
voltage regulators can be used to power each section
to provide enhanced noise immunity. In all cases, each
power pin should have a dedicated 1µF decoupling
capacitor placed as close to the iC-TW28 as possible.
In pin configuration mode, xCALIB can be permanently
tied to ground to eliminate calibration entirely if de-
sired. This permanently enables auto-calibration, and
the iC-TW28 will calibrate itself automatically at every
start-up.
If push-button calibration is not required, xCALIB should
be connected to 3.3 V to avoid spurious calibration.
Reference Outputs
The reference outputs VREF and VC must each be
decoupled to ground with separate 100 nF capacitors
placed as close to the iC-TW28 as possible. VC should
not be used to bias external circuitry or the sin/cos
inputs with single-ended sensors.