| The iC-TW28 is a general purpose 10-bit application-specific interpolator for sine/cosine
signals with automatic calibration and adaption of signal path parameters during operation
to maintain minimum angular error and jitter. Angular position is calculated ata
programmable resolution of up to 1024 increments per input cycle. Automatic calibration
and adaption (correction during operation) of sensor offset, sin/cos amplitude match, and
phase quadrature is provided.Additionally, automatic calibration of gain, offset and phase of
the zero inputs allows for rapid commissioning.
The iC-TW28 accepts 13 mV to 2 V differential Sin/-Cos input signals directly from magnetic
or optical sensors – no external signal conditioning is required in most applications.
The differential zero 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 outputs is fully programmable.
In addition to industry-standard incremental ABZ quadrature output, the iC-TW28 provides
optional UVW commutation output modes for 1 to 32 polepair motors and SPI angle and
multi-cycle readout for embedded applications. The incremental ABZ quadrature output
can be generated at a frequency of up to 12 MHz (20 ns edge spacing); the maximum
output frequency can also be limited so as not to overwhelm connected counters or
controllers. In SPI mode, the iC-TW28 provides multi-cycle synchronization and reference
mark capture functions to support absolute position systems. Higher input signal
frequencies are allowed in SPI mode since the ABZ output frequency limitation is not
The iC-TW28 offers two configuration modes. Pin configuration mode provides simple,
static configuration that does not require any programming or complicated calibration.
Pin configuration mode uses a subset of the iC-TW28’s complete capabilities including
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 values to the internal EEPROM. In more sophisticated
applications, serial configuration mode allows access to all iC-TW28 features. Complete
device configuration using the bi-directional SPI or Encoder Link ports provides access
to all resolutions (including fractional interpolation), fully programmable hysteresis,
and advanced noise/jitter filtering, quality monitoring, and fault detection capabilities.
The iC-TW28 requires no external components for operation. An EEPROM for storage
of configuration and calibration data, and RS422 line drivers are already integrated on-chip.
An integrated power-on reset circuit can be overridden by an external hardware reset signal