IC-TW28 Datasheet, PDF (15/80 Pages) IC-Haus GmbH – 10-BIT SIN/COS INTERPOLATOR

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Rev D2, Page 15/80
FUNCTIONAL BLOCK DIAGRAM
A functional block diagram of the iC-TW28 is shown in
Figure 9 and explained on the following pages.
SIN
Amplifier
Offset
COS
iC-TW28
ADC
ADC
Sin/Cos
Error
Correction
ATAN
Filter
ZERO
VC
VREF
50 MHz
Oscillator
References
xRST
Power-on Reset
ADC
ZERO
Error
Correction
Comparator
Control
Sin/Cos
Adaption
LED Intensity
Control
EEPROM
ZERO Adaption
Push-button
Auto-calibration
Signal Quality
Monitor
Filter Adaption
Fault Handling
IRQ Generation
LED
xCALIB
xIRQ
ABZ and
UVW
Generator
Multycycle
Counter
Position
Capture
Encoder Link
Interface
SPI
Pin
Configuration
RS422
Z
B
A
PINCFG
xSS/C0
SCLK/C1
SI/C2
SO/C3
Figure 9: Functional Block Diagram
Reference
The Reference provides reference voltages for the inter-
nal analog circuits. These outputs must be capacitively
bypassed for proper operation of the iC-TW28.
Oscillator
The Oscillator provides a high-accuracy 50 MHz clock
that controls all timing within the iC-TW28.
Power-On Reset
The Power-On Reset (POR) circuit provides orderly
startup of the iC-TW28 when power is applied. An ex-
ternal reset source can also be connected to the POR
to allow independent control of device startup.
SPI Port/Configuration Pins
When the iC-TW28 is in serial configuration mode, the
SPI port is available for use by an external host proces-
sor or microcontroller for initial calibration or general
communication. In pin configuration mode, the SPI
port is disabled and the SPI pins are used to directly
configure the iC-TW28.
Link can only be used for configuration and diagnostics,
it cannot be used to read the multi-cycle counter or
captured position values. In serial configuration mode,
Encoder Link can be disabled to eliminate tampering
with finished products.
Input Stage
Three programmable gain amplifiers are used to am-
plify the sin, cos, and zero inputs. The sin/cos PGAs
also provide configurable 9 dB attenuation to allow high
amplitude (rail-to-rail) sensor inputs to be used (from
GMR or TMR sensors, for example). A noise filter fol-
lows each PGA to reduce high-frequency noise coming
from the sin/cos inputs. In Serial configuration mode,
two different settings are available for the sin/cos noise
filters.
Analog Error Correction
Coarse analog offset and gain correction is provided to
scale and adjust the sin/cos signals prior to A/D con-
version. These correction values are determined using
auto calibration during initial system calibration.
Encoder Link Interface
The Encoder Link interface provides read/write access
to the iC-TW28’s internal registers using the A+ and A-
outputs. This is useful for field reconfiguration or diag-
nostics of products incorporating the iC-TW28. Encoder
Analog-to-Digital Converters (ADCs)
10-bit ADCs convert the conditioned analog sin and cos
signals into digital values for further processing. An
8-bit ADC is used for the zero signal. The remainder of
the signal path is completely digital.