iC-TW8 16-BIT SIN/COS INTERPOLATOR
Pin Configuration Mode
Jan 9, 2013 Page PC5/15
Connecting an Index Sensor (If Used)
Connecting the EEPROM
The iC-TW8 can interface to a wide range of in-
dex sensors or gating sources to provide an index
or Z output which is synchronized with the AB
outputs. Digital Hall sensors are often used for
this purpose, as shown in Figure 6.
The iC-TW8 requires a 24xx02 through 24xx16 fami-
ly I2C EEPROM for storage of sensor calibration data
(offset, gain, etc.). The EEPROM connects directly to
the iC-TW8 via a dedicated I2C communication chan-
nel using SCL (pin 27) and SDA (pin 28) as shown in
Figure 7. No external pull-up resistors are required.
EESEL (pin 4) of the TW8 must also be connected to
DVSS as shown.
VDD
iC-TW8
VDD
ZERO+
DVDD
EESEL tied to DVSS.
VDD
EESEL
1µF
ZERO-
DVSS
Digital Hall
active low
VDD
SCL
SDA
WP
SCL VCC
Figure 6: Index Sensor Connection
1µF
SDA
VSS
Digital sensors (Hall, MR, and others) typically
provide an active-low signal via an open-drain
output that pulls low in the presence of a magnetic
field. Connect an active-low (open drain) digital
index sensor to the iC-TW8 ZERO– input (pin 48)
and connect the ZERO+ input (pin 47) to a resis-
tive voltage divider set to the midpoint of the in-
dex sensor output voltage swing to provide good
noise rejection. For active-high (open source) dig-
ital index sensors, reverse the ZERO+ and
ZERO– connections.
WP
EEPROM
24xx
iC-TW8
Figure 7: EEPROM Connection
In pin configuration mode, the Write Protect (WP)
input of the EEPROM is not controlled by the iC-
TW8. WP must be grounded (disabled) during config-
uration to allow the iC-TW8 to write the auto-adapted
parameters to the EEPROM. In operation, WP can be
left grounded (write protection disabled) as shown in
Figure 7, or connected to DVDD by additional circuit-
ry (such as a jumper) for parameter protection.
To guarantee one and only one Z output from the
iC-TW8 over multiple Sin/Cos input cycles, the
ZERO input signal must be roughly centered on
(in phase with) the Cos+ incremental sensor sig-
nal and no larger than 1.5 Sin/Cos input cycles
under all conditions.
If no index (Z) output is required, connect
ZERO+ (pin 47) to ground and ZERO– (pin 48)
to AVDD.
Analog-output index sensors can also be used
with the iC-TW8, but only in SPI/1-wire configu-
ration mode.
Copyright © 2011–2013 iC-Haus
www.ichaus.com
ICHAUS [ IC-HAUS GMBH ]
