IC-TW11 Datasheet, PDF (9/25 Pages) IC-Haus GmbH – 10-BIT ULTRA LOW POWER MAGNETIC ABSOLUTE ROTARY ENCODER

iC-TW11 10-BIT ULTRA LOW POWER^preliminary
MAGNETIC ABSOLUTE ROTARY ENCODER
FUNCTIONAL BLOCK DIAGRAM
Rev B1, Page 9/25
Hall Array
SAMPLE
IRQ_IN
Sample
Timing
Amplifiers
Analog-to-Digital
Filters
Converters
PGA
ADC ^120°
Sin
PGA
ADC
0°
3ø/2ø
Transform
Arc
Tangent
Cos
240°
PGA
ADC
Angle
Automatic Gain Control
(AGC)
SPI
Port
xSS
SCLK
SI
SO
IRQ_OUT
Figure 2: Block diagram
Hall Array
Three Hall effect sensors are integrated into the
iC-TW11 to directly sense the angular position of a
dipole permanent magnet positioned over the chip. The
three sensors are equally spaced (120° apart) on a
Ø 2 mm circle centered on the 4x4 mm package.
Programmable Gain Amplifiers
Three programmable gain amplifiers condition and am-
plify the signals from the three Hall sensors. 18 gain
values in steps of approximately 1.5 dB are available
to properly match the sensor voltages to the ADCs for
highest conversion accuracy.
Filters
The three conditioned Hall signals are each filtered by
first-order 10 kHz filters to reduce sampling noise and
improve measurement stability and accuracy. These
filters can be disabled to lower power consumption and
to allow faster sampling rates.
3Ø/2Ø Transform
The three-phase Hall signals are next converted to
equivalent sine and cosine values using a Clarke trans-
form algorithm.
Arc-Tangent
Finally, a CORDIC arc-tangent algorithm calculates the
angular position of the permanent magnet based on the
converted sin and cos values.
SPI Port
The iC-TW11 uses a standard SPI (serial peripheral in-
terface) slave port for all communication. This includes
sampling and reading the angular position as well as
reading and writing internal registers.
Automatic Gain Control
By default, the iC-TW11 automatically sets and main-
tains the optimum gain value for all three Hall channels
to ensure accurate conversion. The AGC can be dis-
abled and the gain set manually via SPI commands if
required for special applications.
Analog-to-Digital Converters (ADCs)
Three ADCs convert the conditioned and filtered Hall
signals into 10-bit digital values. The remainder of the
signal path is completely digital.
Sample Timing
By default, sampling is initiated by a rising edge on the
xSS pin or a falling edge on the SAMPLE pin. Sampling
powers up the Hall array and analog circuitry, measures