iC-TW8 16-BIT SIN/COS INTERPOLATOR
Serial Configuration Mode
Jan 9, 2013 Page SC10/36
Electrical Connections
The basic electrical connections for an encoder us-
ing the iC-TW8 are shown in Figure 8. Other than
the analog sensor, only an EEPROM for parameter
storage and a few bypass capacitors are required for
operation. PINSEL (pin 22) must be connected to
DVSS to select serial configuration mode and either
the SPI or 1-wire serial ports must be connected to
an appropriate master for configuration. A voltage
regulator to supply clean power to the device and a
line driver are recommended. A crystal or oscillator
(clock driver) is recommended for all but the most
cost-sensitive applications.
Analog power (AVDD = pin 38) and digital power
(DVDD = pin 21) inputs must be connected to a low
impedance 5V or 3.3V power source, preferably an
on-board voltage regulator. In addition, AVDD and
DVDD should each have a dedicated 1µF decou-
pling capacitor placed as close to the power pins on
the device as possible.
If the iC-TW8 is used with a line driver (such as the
iC-HD7 or iC-HX) or a high frequency FPGA, it is
especially important to isolate the iC-TW8 power
inputs (AVDD and DVDD) against external noise.
In such applications, a dual voltage regulator such
as the iC-DC is highly recommended. Note that both
AVDD and DVDD must be the same voltage level
(5V or 3.3V).
The iC-TW8 requires a high quality ground and
clean power supplies. Analog ground (AVSS = pin
46) and digital ground (DVSS = pin 15) must both
be connected on the PCB to a solid ground plane.
VDD_MAIN
Regulator
VDD_TW8
10µF
PINSEL tied to DVSS for
Serial Configuration mode
VDD_TW8
VDD_TW8
AVDD
AVSS
DVDD
PINSEL
EESEL tied to DVSS.
1µF
1µF
EESEL
DVSS
MR Sensor
Line Driver
SIN+
SIN-
OUTA
OUTB
OUTZ
COS+
COS-
CALIB
SPI_SO
SPI_SI
Calibration Button
SPI Communication Port
SPI_SCLK
SPI_xSS
}
VREF
VC
1-Wire Communication Port
VDD_TW8
IR
1µF
1µF
EEPROM
24AA02
SCL
SDA
WP
SCL
SDA
iC-TW8
WP
Figure 8: iC-TW8 Electrical Connections (Serial Configuration Mode)
Both pin VC (pin 44) and VREF (pin 45) must be
decoupled to ground with 1µF each as shown. The
EEPROM and the line driver (if used) must be de-
coupled according to their respective requirements.
The calibration button provides an easy means to
activate the auto-calibration feature of the iC-TW8
to set the data path parameters (offset, gain, and
phase) to their optimal values. All pins not explicitly
shown in Figure 8 should be connected to appropri-
ate levels as indicated under Pin Functions in the iC-
TW8 data sheet.
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