IC-TW8_16 Datasheet, PDF (2/67 Pages) IC-Haus GmbH – 16-BIT SIN/COS INTERPOLATOR

iC-TW8 16-BIT SIN/COS INTERPOLATOR
WITH AUTO-CALIBRATION
Rev C2, Page 2/67
DESCRIPTION
The iC-TW8 is a 16-bit application-specific DSP inter-
polator for sine/cosine signals with automatic calibra-
tion and adaption of signal path parameters during
operation to maintain minimum angular error and jit-
ter. Angular position is calculated at a programmable
resolution of up to 65,536 increments per input cycle.
Automatic calibration and adaption (correction during
operation) of sensor offset, Sin/Cos amplitude match,
and phase quadrature is provided. Additionally, a
64-byte lookup table (LUT) is available to correct for
residual harmonic distortion in the sensor signals.
The iC-TW8 accepts 10 mV to 700 mV differential Sin/-
Cos input signals directly from magnetic or optical
sensors – no external signal conditioning is required
in most applications. The differential zero (reference)
input accepts a wide range of digital and analog index
gating sources such as Hall or MR sensor bridges.
The Z output width, position relative to the Sin/Cos
inputs, and synchronization to the AB quadrature out-
puts is fully programmable.
In addition to industry-standard incremental ABZ
quadrature output, the iC-TW8 provides optional
PWM (potentiometer) and serial-only (SPI or 1-wire)
output modes for special or imbedded applications.
The incremental ABZ quadrature output can be gen-
erated at a frequency of up to 8 MHz (31 ns edge
spacing); the maximum output frequency can also be
limited so as not to overwhelm connected counters.
In PWM output mode, the iC-TW8 provides a differen-
tial pulse-width modulated signal proportional to the
calculated angle (position) of the Sin/Cos inputs. An
RC filter may be used to provide an analog voltage
output for potentiometer applications, or to drive an
external ADC for simple single-turn absolute applica-
tions. Synchronous digital filters may be implemented
using an external microcontroller or FPGA for more
sophisticated or imbedded applications.
In serial-only output mode, the iC-TW8’s internal
32-bit position counter and instantaneous angular ve-
locity register can be read via the built-in SPI or 1-wire
serial ports at clock rates of up to 32 MHz. Higher
input signal frequencies are allowed in serial-only out-
put mode since the ABZ output frequency limitation is
not applicable.
The iC-TW8 offers two configuration modes. Pin con-
figuration mode provides simple, static configuration
that does not require any programming or complicated
calibration. Pin configuration mode uses a subset
of the iC-TW8’s complete capabilities including ABZ
quadrature output, a limited choice of the most com-
monly used interpolation (resolution) and hysteresis
values, and one-button calibration. Eight resistors
set voltage levels at four configuration input pins to
select all operating parameters, simplifying product
assembly. One-button auto calibration sets input gain
and compensates sensor offset and Sin/Cos channel
gain match and phase with just a few input cycles and
then stores the compensation values to EEPROM.
In more sophisticated applications, serial configura-
tion mode allows access to all iC-TW8 features. Com-
plete device configuration using the bi-directional SPI
or 1-wire serial ports provides access to all resolu-
tions (including fractional interpolation), the sensor
distortion LUT, fully programmable hysteresis, and
advanced noise/jitter filtering, quality monitoring, and
fault detection capabilities.
The iC-TW8 requires only two external components
for operation, a serial EEPROM for storage of con-
figuration and calibration data, and a clock oscillator
or crystal. An internal RC oscillator is provided for
cost-sensitive applications. Split analog and digital
power supply inputs allow optimal filtering for noisy
industrial environments. An integrated power-on re-
set circuit can be overridden by an external hardware
reset signal if necessary.