IC-TW3 Datasheet, PDF (21/24 Pages) IC-Haus GmbH – SENSOR SIGNAL CONDITIONER WITH TEMPERATURE COMPENSATION AND LINE DRIVER

iC-TW3 SENSOR SIGNAL CONDITIONER WITH
TEMPERATURE COMPENSATION AND LINE DRIVER
TEMPERATURE COMPENSATION
Rev B1, Page 21/24
Temperature compensation is enabled by setting con-
trol bit TEMP of register 0x01. A piece-wise linear in-
terpolation of values stored in a look-up-table (LUT) is
employed to calculate the gain and offset for a given
temperature. Figure 6 shows a sample configuration
with seven breakpoints.
TEMP
Code
0
1
Adr 0x01; Bit 0
R/W
Function
Temperature compensation is disabled (default)
Temperature compensation is enabled
Table 41: Temperature compensation enable
gain/ofs
ofsZ
ofsB
ofsA
gainB
gainA
bp0
bp1
bp2
bp3 bp4
bp5
0
ADC value
bp6
255
Figure 6: LUT with seven breakpoints
There can be a minimum of two up to a maximum
of 16 temperature breakpoints within the LUT. Each
breakpoint has five interpolation values associated to it
namely GAINA, GAINB, OFSA, OFSB and OFSZ. For
more details on the layout of the LUT refer to section
"EEPROM" on page 11.
Breakpoints can be placed freely across the temper-
ature axis except for the first and the last breakpoint.
The first breakpoint must be located at ADC value 0
(which roughly corresponds to -50 °C when using the
internal sensor), the last breakpoint must be located at
ADC value 255 (150 °C with the internal sensor).
The LUT is stored in the off-chip EEPROM from mem-
ory location 0x10 onward. Note that the EEPROM ad-
dress space maps to the 1-wire address 128. Access-
ing EEPROM address 0 is therefore equivalent to ac-
cessing memory location 128 through the 1-wire inter-
face. The breakpoint entry with a value of 255 marks
the last valid LUT entry. All addresses thereafter in-
cluding their data will be ignored.
Temperature dependent gain and offset is determined
by performing linear interpolation between break-
points. Temperature dependent gain and offset are
TGAINA/B and TOFSA/B respectively.
Fine gain FGAINA/B and fine offset FOFSA/B (see fig-
ure 4 on page 14) are calculated as follows:
fgain = tgain + dgain
fofs = tofs + dofs
Whereas TGAIN and TOFS are the temperature de-
pendent values calculated using the LUT and DGAIN
and DOFS are registers updated either manually or by
the automatic compensation function.