iC-TW3 SENSOR SIGNAL CONDITIONER WITH
TEMPERATURE COMPENSATION AND LINE DRIVER
Rev B1, Page 16/24
Z SIGNAL PATH (INDEX)
A third analog path is used for index signal processing output referred offset correction. This is used to elimi-
frequently found in encoder applications. Refer to Fig- nate inherent amplifier offset as well as sensor offset.
ure 5 for an overview. An input amplifier with a gain Additionally, the same offset correction is used to skew
range of 0 to 36 dB is used to amplify the index signal the comparator shift point to a desired level. The offset
to an intermediate level. The input amplifier employs correction is temperature compensated with a LUT.
VDD
ENSIGZ
OFSZ(5:0)
BYPASSZ
ZO
PINZ
NINZ
+
+
+
+
output
1Vpp
NZO
-
-
-
POLARITYZ
GAINZ(2:0)
MODEZ
OGAINZ(1:0)
SINGLEINZ
VDD/2
Figure 5: The Z signal path
Input Amplifier
0..36 dB
Output Amplifier
-3 dB, 0 dB, 6 dB
Composite
Gain range
Gain step
-3..42 dB
6 dB
1.86V
input
1.86V
input
Offset Range (input
referred*
gain
gain
60mV
input
Offset step input referred
gain
*: gaininput = 10gain_of_input_amplifier_in_dB
20
Table 18: Gain and offset characteristics for channel Z
MODEZ
Adr 0x02; Bit 3
R/W
A single ended input referenced to VDD/2 is provided
Code
Function
by setting bit SINGLEINZ of register 0x02. Alterna-
0
1
1 Vpp out (default)
Rail-to-rail output
tively, pin NINZ can be biased with an external voltage.
(requires OGAINZ(1:0) set to 0x2)
SINGLEINZ
Adr 0x02; Bit 1
Function
R/W
Code
Table 20: Channel Z output mode select
0
1
channel Z input is differential (default)
channel Z is single ended
BYPASSZ
Adr 0x02; Bit 2
Function
R/W
Code
Table 19: Single ended input functionality
0
1
Comparator is enabled (default)
Comparator is bypassed
A zero-crossing comparator generates a 1.0 Vpeak-peak
output signal or a rail-to-rail signal depending on con-
trol bit MODEZ. The comparator can be bypassed
which allows using the Z Path as a regular amplifier
path. Bypassing can be toggled via bit BYPASSZ of
register 0x02.
Table 21: Channel Z comparator bypass
ICHAUS [ IC-HAUS GMBH ]
