iC-TW8 16-BIT SIN/COS INTERPOLATOR
WITH AUTO-CALIBRATION
Rev A2, Page 2/12
DESCRIPTION
The iC-TW8 is a 16-bit application-specific DSP inter- In serial-only output mode, the iC-TW8’s internal 32-
polator for sine/cosine signals with automatic calibra- bit position counter and instantaneous angular veloc-
tion and adaption of signal path parameters during ity register can be read via the built-in SPI or 1-wire
operation to maintain minimum angular error and jit- serial ports at clock rates of up to 32 MHz. Higher in-
ter. Angular position is calculated at a programmable put signal frequencies are allowed in serial-only out-
resolution of up to 65,536 increments per input cy- put mode since the ABZ output frequency limitation
cle. Automatic calibration and adaption (correction is not applicable.
during operation) of sensor offset, Sin/Cos amplitude
match, and phase quadrature is provided. Addition- The iC-TW8 offers two configuration modes. Pin
ally, a 64-byte lookup table (LUT) is available to cor- configuration mode provides simple, static configura-
rect for residual harmonic distortion in the sensor sig- tion that does not require any programming or com-
nals.
plicated calibration. Pin configuration mode uses a
subset of the iC-TW8’s complete capabilities includ-
The iC-TW8 accepts 10 mV to 700 mV differential ing ABZ quadrature output, a limited choice of the
Sin/Cos input signals directly from magnetic or op- most commonly used interpolation (resolution) and
tical sensors – no external signal conditioning is re- hysteresis values, and one-button calibration. Eight
quired in most applications. The differential zero (ref- resistors set voltage levels at four configuration input
erence) input accepts a wide range of digital and ana- pins to select all operating parameters, simplifying
log index gating sources such as Hall or MR sen- product assembly. One-button auto calibration sets
sor bridges. The Z output width, position relative to input gain and compensates sensor offset and Sin/-
the Sin/Cos inputs, and synchronization to the AB Cos channel gain match and phase with just a few
quadrature outputs is fully programmable.
input cycles and then stores the compensation val-
ues to EEPROM.
In addition to industry-standard incremental ABZ
quadrature output, the iC-TW8 provides optional In more sophisticated applications, serial config-
PWM (potentiometer) and serial-only (SPI or 1-wire) uration mode allows access to all iC-TW8 fea-
output modes for special or imbedded applications. tures. Complete device configuration using the bi-
The incremental ABZ quadrature output can be gen- directional SPI or 1-wire serial ports provides ac-
erated at a frequency of up to 8 MHz (31 ns edge cess to all resolutions (including fractional interpola-
spacing); the maximum output frequency can also be tion), the sensor distortion LUT, fully programmable
limited so as not to overwhelm connected counters.
hysteresis, and advanced noise/jitter filtering, quality
monitoring, and fault detection capabilities.
In PWM output mode, the iC-TW8 provides a differ-
ential pulse-width modulated signal proportional to The iC-TW8 requires only two external components
the calculated angle (position) of the Sin/Cos inputs. for operation, a serial EEPROM for storage of con-
An RC filter may be used to provide an analog volt- figuration and calibration data, and a clock oscillator
age output for potentiometer applications, or to drive or crystal. An internal RC oscillator is provided for
an external ADC for simple single-turn absolute ap- cost-sensitive applications. Split analog and digital
plications. Synchronous digital filters may be imple- power supply inputs allow optimal filtering for noisy
mented using an external microcontroller or FPGA industrial environments. An integrated power-on re-
for more sophisticated or imbedded applications.
set circuit can be overridden by an external hardware
reset signal if necessary.
ICHAUS [ IC-HAUS GMBH ]
