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iC-TW8
16-BIT SIN/COS INTERPOLATOR
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FEATURES
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
Input frequency of up to 125 kHz
Binary/decimal interpolation factors from x0.25 to x16384
Post-AB divider [1/1 to 1/32] allows fractional resolution
Differential sine/cosine input signal range of
20 mV to 1.4 V peak-peak
Automatic offset, gain match and phase correction
Simple automatic one-pin calibration
Easy configuration: by static pins (for generic ABZ output)
Advanced configuration: 1-wire interface, 3 and 4-wire SPI
(32 MHz), serial I
2
C EEPROM
PWM or ABZ quadrature encoder output signals
Incremental ABZ output to 8 MHz (32 MHz edge separation)
Position and velocity read-out (32 bit SPI)
Sophisticated error handling and signal monitoring
Static 64 position LUT to compensate for arbitrary sensor
distortions
Supply voltage range of 3.1 V to 5.5 V
Extended temperature range of -40 to +125 °C
APPLICATIONS
o
Sine/cosine interpolation
o
Signal conditioning with auto
calibration
o
Linear and rotary encoders
o
Flexible incremental encoder
systems
PACKAGES
QFN48 7x7
BLOCK DIAGRAM
AVDD
SIN+
SIN-
+
_
DVDD
OUTA
ADC
QUADRATURE
PWM
GENERATOR
DIGITAL
SIGNAL
PROCESSING
EEPROM
MASTER
OUTB
OUTZ
COS+
COS-
+
_
ADC
ZERO+
ZERO-
+
_
SDA
SCL
WP
XIN
XOUT
VC
VREF
CRYSTAL
DRIVER
BANDGAP
EESEL
iC-TW8
MEMORY
1-WIRE
INTERFACE
IR
SPI_SO
xRST
RESET
SPI_SI
SPI
SPI_SCLK
SPI_xSS
FAULT
STATUS
FRAME
CLOCK
CALIB
FAB
PINSEL
AVSS
DVSS
C3
CONTROL
PIN
CONFIG.
INTERFACE
C2
C1
C0
Copyright © 2013 iC-Haus
http://www.ichaus.com
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iC-TW8
16-BIT SIN/COS INTERPOLATOR
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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.
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16-BIT SIN/COS INTERPOLATOR
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CONTENTS
PACKAGING INFORMATION
PIN CONFIGURATION QFN48-7x7
(topview) . . . . . . . . . . . . . . . . .
PIN FUNCTIONS
. . . . . . . . . . . . . . .
4
4
4
7
7
8
OPERATING REQUIREMENTS: SPI/1-wire In-
terface
ADDITIONAL INFORMATION
DESIGN REVIEW: Function Notes
REVISION HISTORY . . . . . . . . . . . . .
ATTACHMENTS
PC: Description of Pin Configuration Mode .
SC: Description of Serial Configuration Mode
10
11
11
11
13
13
28
ABSOLUTE MAXIMUM RATINGS
THERMAL DATA
ELECTRICAL CHARACTERISTICS
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PACKAGING INFORMATION
PIN CONFIGURATION QFN48-7x7
(topview)
PIN FUNCTIONS
No. Name Function
38 AVDD +3.1 V to 5.5 V Analog Supply Voltage
AVDD and DVDD can be powered either
mutually or separately but must be the
same voltage.
46 AVSS Analog Ground
AVSS must be connected to DVSS ex-
ternally.
21 DVDD +3.1 V to 5.5 V Digital Supply Voltage
15 DVSS Digital Ground
TP
Connect the backside paddle to a
ground plane which must have AVSS
potential.
Refer to the following table for a detailed
description.
... other
PIN FUNCTIONS
No. Name
1
2
nc
xRST
Digital in,
low active,
40 kΩ pull-up
Digital in,
5 kΩ pull-down
Reset Input
I/O
Function
Description
Pin has no connection to die. Connect to DVSS on PCB.
The device is held in reset as long as xRST is low.
For operation at 5 V, connect 68 kΩ to DVSS (changes the power-on-
reset threshold to approx. 4 V). Refer to section Power-on-Reset and
Startup for more information on reset.
Fabrication test is enabled when pin is high during reset. This pin must
be connected to DVSS for normal operation.
Pin must be tied low.
Device enters calibration mode on falling edge of CALIB. Adaptation
parameters are written to the external eeprom on rising edge of CALIB.
This pin should be left floating or connected to DVDD if not used.
The pin is a programmable clock output that can be used for PWM
synchronization.
A connection to DVSS is advisable when not in use.
Pin is bi-directional. Refer to Programmer’s Reference for more details.
This pin outputs the internal ADC sampling clock, which can be used to
synchronize downstream circuits.
A connection to DVSS is advisable when not in use.
Pin directly connects to an SPI master MI pin.
Pin directly connects to SPI master MO pin.
This pin should be tied to DVSS if the SPI is not used.
3
4
5
FAB
EESEL
CALIB
Test Enable Input
Digital in,
Selection Input
150 kΩ pull-down
Digital in,
10 kΩ pull-up,
hysteresis
Calibration Control
6
CLOCK
Digital in/out,
Clock Output
150 kΩ pull-down
Digital in/out,
150 kΩ pull-up
1-Wire Interface I/O
7
8
IR
FRAME
Digital in/out,
Sync Output
150 kΩ pull-down
Digital out
Digital in
SPI Slave Output
SPI Slave Input
9
10
SPI_SO
SPI_SI
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iC-TW8
16-BIT SIN/COS INTERPOLATOR
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Rev A2, Page 5/12
PIN FUNCTIONS
No. Name
11
SPI_SCLK
I/O
Digital in,
with hysteresis
Function
SPI Slave Clock Input
Description
Pin connects to SPI master clock output. The input implements hys-
teresis to avoid double triggering.
This pin must be tied to DVSS if the SPI is not used.
These pins have no connection to die. Connect to DVSS on PCB.
Digital in,
low active
Ground
Digital out
Digital out
SPI Slave Select Input
In 4-pin SPI mode this pin directly connects to the SPI master slave
select output. In case the SPI is operated in 3-pin mode, SPI_xSS
must be tied low to DVSS.
Pin must tie to high quality ground, usually a solid PCB plane.
Quadrature interface reference output.
In quadrature mode this is output B.
In PWM mode this is PWM-, the inverted output of OUTA.
In Z calibration mode (bit RB_TEST1.z_test = 1) this is the Z window
seen just after the input comparator.
In quadrature mode this is output A.
In PWM mode this is PWM+.
In Z calibration mode (bit RB_TEST1.z_test = 1) this is the Z window
used to gate the Z output.
This pin provides proportional status information. Pin can drive a
10 mA LED and is widely configurable. Refer to section Monitoring
Interpolation Quality for details.
Pin is low on error and is capable of driving a 10 mA LED. The error
response can be configured as detailed in section Fault Handling for
details.
+3.1 V to +5.5 V supply voltage terminal.
DVDD and AVDD must be the same voltage level (5 V or 3.3 V).
Tie pin to DVSS to enable serial configuration mode.
Tie pin to DVDD to select pin configuration mode.
These pins have no connection to die. Connect to DVSS on PCB.
Connect this pin to DVSS on PCB.
Digital in/out,
10 kΩ pull-up
Digital in/out,
10 kΩ pull-up
Digital out
EEPROM Clock Line
EEPROM Data Line
EEPROM Write Protection
This pin connects to the EEPROM SCL pin. No external I2C pull-up
resistor is required as 10 kΩ is integrated.
This pin connects to the EEPROM SDA pin. No external I2C pull-up
resistor is required as 10 kΩ is integrated.
This pin acts as the write protect signal and connects to the EEPROM
WP pin. No external pull-up is required as this pin is a push-pull output
actively driving low and high.
If the pin configuration mode is used (pin PINSEL tied high), each pin
functions as 12-level configuration input.
If serial configuration mode is used (pin PINSEL tied low), connect
these pins to DVSS on PCB.
Pin can be left floating if no crystal is used.
An external oscillator or other square wave clock source can be used
to drive this pin. Refer to Providing a Clock.
Pin must be tied to AVSS if no crystal is used.
These pins have no connection to die. Connect to DVSS on PCB.
Supply
Analog in
Analog in
Analog in
Analog in
Analog out
Analog Power Supply
Sine Input +
Sine Input -
Cosine Input +
Cosine Input -
Bias Output
+3.1 V to +5.5 V supply voltage terminal. Keep it clean!
DVDD and AVDD must be the same voltage level (5 V or 3.3 V).
Differential sine signal input. For single ended sensors SIN- must be
biased to an appropriate DC level.
Differential cosine signal input. For single ended sensors COS- must
be biased to an appropriate DC level.
Pin has no connection to die. Connect to DVSS on PCB.
Decouple with 1 µF capacitor to AVSS. Do not inject noise into this pins
as it directly impacts ADC conversion noise.
12
13
14
nc
nc
SPI_xSS
15
16
17
DVSS
OUTZ
OUTB
Digital Ground
Z Output
B Output
PWM- Output
Z Window
A Output
PWM+ Output
Z Window
PWM Status Output
18
OUTA
Digital out
19
STATUS
Digital out
20
FAULT
Digital out
Error Status Output
21
22
23
24
25
26
27
28
29
DVDD
PINSEL
nc
nc
nc
reserved
SCL
SDA
WP
Supply
Digital Power Supply
Digital in,
Configuration Mode
150 kΩ pull-down Selection
30
31
32
33
34
C0
C1
C2
C3
XOUT
Analog in
Configuration
Inputs
Analog in/out
Crystal Terminal
35
36
37
38
39
40
41
42
43
44
XIN
nc
nc
AVDD
SIN+
SIN-
COS+
COS-
nc
VC
Analog in
Crystal Terminal
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