IC-TW8_13 Datasheet, PDF (2/63 Pages) IC-Haus GmbH – 16-BIT SIN/COS INTERPOLATOR WITH AUTO-CALIBRATION

iC-TW8 16-BIT SIN/COS
WITH AUTO-CALIBRATION
INTERPOLATO_pR_reliminary
Rev A2, Page 2/12
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 cy-
cle. Automatic calibration and adaption (correction
during operation) of sensor offset, Sin/Cos amplitude
match, and phase quadrature is provided. Addition-
ally, a 64-byte lookup table (LUT) is available to cor-
rect for residual harmonic distortion in the sensor sig-
nals.
The iC-TW8 accepts 10 mV to 700 mV differential
Sin/Cos input signals directly from magnetic or op-
tical sensors – no external signal conditioning is re-
quired in most applications. The differential zero (ref-
erence) input accepts a wide range of digital and ana-
log index gating sources such as Hall or MR sen-
sor bridges. The Z output width, position relative to
the Sin/Cos inputs, and synchronization to the AB
quadrature outputs 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 differ-
ential 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 volt-
age output for potentiometer applications, or to drive
an external ADC for simple single-turn absolute ap-
plications. Synchronous digital filters may be imple-
mented 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 veloc-
ity register can be read via the built-in SPI or 1-wire
serial ports at clock rates of up to 32 MHz. Higher in-
put 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
configuration mode provides simple, static configura-
tion that does not require any programming or com-
plicated calibration. Pin configuration mode uses a
subset of the iC-TW8’s complete capabilities includ-
ing ABZ quadrature output, a limited choice of the
most commonly 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 val-
ues to EEPROM.
In more sophisticated applications, serial config-
uration mode allows access to all iC-TW8 fea-
tures. Complete device configuration using the bi-
directional SPI or 1-wire serial ports provides ac-
cess to all resolutions (including fractional interpola-
tion), 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.