iC-TW3 SENSOR SIGNAL CONDITIONER WITH
TEMPERATURE COMPENSATION AND LINE DRIVER
Rev B1, Page 18/24
AUTOMATIC COMPENSATION
DYNAMIC
Adr 0x01; Bit 1
Function
R/W
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.
Code
0
1
Automatic function is disabled
Automatic function is enabled
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.
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.
VEXT
Code
0
Adr 0x02; Bit 7
Function
R/W
FREQ(1:0)
Adr 0x01; Bit 4:3
Function
R/W
Internally generated 1 V or 2 V is used as output
target voltage, depending on register OGAIN(1:0).
Code
00
no tracking limit (default)
1
Voltage applied to pin VC defines target output
voltage (see Table 29).
01
200 kHz
20 kHz
2 kHz
10
11
Table 28: Target voltage selection
Table 31: Automatic compensation adaption rate
Target Output
OGAIN(1:0) Output Gain
VEXT
Voltage Vppdiff
00
01
10
11
00
01
10
11
0 dB
0
0
0
0
1
1
1
1
1 V
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.
reserved
6 dB
2 V
-3 dB
1 V
0 dB
2.21 V - V(VC)
reserved
6 dB
(2.21 V - VC) x 2
2.21 V - VC
-3 dB
GENTLE
Adr 0x01; Bit 2
Function
R/W
Code
Table 29: Target output voltages
0
1
Gain and offset are updated simultaneously
Gain and offset are updated alternately
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.
Table 32: Automatic compensation sequence control
Control bits FREQ(1:0) of register 0x01 are used to Automatic compensation can be used in conjunction
limit the tracking rate. If the input frequency increases with temperature compensation. Automatic compen-
above the limit tracking will stop. Normally, it is not re- sation will then remove any residual offset or gain mis-
quired to limit the tracking frequency although it can be match not corrected by the temperature correction al-
useful for certain bandwidth limited sensors.
gorithm.
ICHAUS [ IC-HAUS GMBH ]
