IC-TW3 Datasheet, PDF (18/24 Pages) IC-Haus GmbH – SENSOR SIGNAL CONDITIONER WITH TEMPERATURE COMPENSATION AND LINE DRIVER

iC-TW3 SENSOR SIGNAL CONDITIONER WITH
TEMPERATURE COMPENSATION AND LINE DRIVER
AUTOMATIC COMPENSATION
Rev B1, Page 18/24
Automatic gain and offset correction is available for
dual sensor bridges that are 90° out of phase. These
types of sensors are used for encoder applications.
Automatic compensation removes any sensor offset
and sets the gain to achieve a fixed output voltage.
The target output voltage depends on the output gain
OGAIN(1:0) as well as on the control bit VEXT. When
using an external reference voltage, the appropriate
voltage must be applied to pin VC.
VEXT
Code
0
1
Adr 0x02; Bit 7
R/W
Function
Internally generated 1 V or 2 V is used as output
target voltage, depending on register OGAIN(1:0).
Voltage applied to pin VC defines target output
voltage (see Table 29).
Table 28: Target voltage selection
OGAIN(1:0) Output Gain
00
0 dB
01
reserved
10
6 dB
11
-3 dB
00
0 dB
01
reserved
10
6 dB
11
-3 dB
VEXT
0
0
0
0
1
1
1
1
Target Output
Voltage V_ppdiff
1V
2V
1V
2.21 V - V(VC)
(2.21 V - VC) x 2
2.21 V - VC
Table 29: Target output voltages
Automatic compensation is enabled by setting control
bit DYNAMIC of register 0x01 to 1. If enabled, it will
constantly alter register DOFSA/B and DGAINA/B to
maintain zero offset and the target output amplitude.
Control bits FREQ(1:0) of register 0x01 are used to
limit the tracking rate. If the input frequency increases
above the limit tracking will stop. Normally, it is not re-
quired to limit the tracking frequency although it can be
useful for certain bandwidth limited sensors.
DYNAMIC
Adr 0x01; Bit 1
R/W
Code
Function
0
Automatic function is disabled
1
Automatic function is enabled
Table 30: Automatic compensation enable
Note that setting FREQ(1:0) to other values than 0
does not affect the signal bandwidth of the amplifier.
It merely limits the rate of automatic adaption.
FREQ(1:0)
Adr 0x01; Bit 4:3
R/W
Code
Function
00
no tracking limit (default)
01
200 kHz
10
20 kHz
11
2 kHz
Table 31: Automatic compensation adaption rate
In normal operation the compensation algorithm will
adjust both gain and offset simultaneously in order to
achieve fast convergence. If control bit GENTLE of
register 0x01 is set, gain and offset registers are up-
dated alternately. This reduces output jumpiness at
the expense of slower convergence.
GENTLE
Code
0
1
Adr 0x01; Bit 2
R/W
Function
Gain and offset are updated simultaneously
Gain and offset are updated alternately
Table 32: Automatic compensation sequence control
Automatic compensation can be used in conjunction
with temperature compensation. Automatic compen-
sation will then remove any residual offset or gain mis-
match not corrected by the temperature correction al-
gorithm.