IC-TW3 Datasheet, PDF (19/24 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 SENSING
Rev B1, Page 19/24
iC-TW3 contains an on-chip temperature sensor. Op-
tionally, an external sensor can be used by setting bit
XCELSIUS of register 0x02 to 1. An external temper-
ature sensor is useful for remote temperature sensing
or in situations where the internal sensor does not pro-
vide adequate accuracy. Also, device self-heating due
to heavy output loads can have an impact on the inter-
nal sensor readings. Connect the external temperature
sensor with its analog output to pin KELVIN.
CCELSIUS(3:0) Adr 0x05; Bit 3:0
R/W
Code
Bit 3 is sign, bits 2:0 are magnitude of correction
1111
most negative correction
...
...
1001
least negative correction
1000
no correction
0000
no correction (default)
0001
least positive correction
...
...
0111
most positive correction
XCELSIUS
Adr 0x02; Bit 6
R/W
Code
Function
0
Select internal temperature sensor (default)
1
Select external temperature sensor
Table 33: Temperature sensor select
Table 34: Coarse offset correction
FCELSIUS(3:0) Adr 0x05; Bit 7:4
R/W
Code
Value added to ADC reading is FCELSIUS(3:0) - 8
0000
-8 (default)
0001
-7
...
...
1111
7
An ADC converts the analog temperature signal into
an 8-bit digital word. In case the on-chip sensor is used
the 8-bit value spans a temperature range of -50 °C to
150 °C. It is recommended to calibrate the ADC using
register 0x05 even when using an external tempera-
ture sensor.
Table 35: Fine offset correction
CELSIUS(7:0) Adr 0x12; Bit 7:0
R
Data
Function
0x00
Current temperature ADC value that is used for
compensation calculations. Value of this register is
0x40 + FCELSIUS(3:0) - 8
0xFF
Table 36: Temperature data
Calibrating the temperature ADC
The raw ADC value can be accessed through register
0x40. A ±2 increment hysteresis is applied to the ADC
value to remove conversion noise and the offset regis-
ter 0x05 is added. The final value is stored in register
0x12 and is used for temperature compensation.
To achieve best temperature accuracy it is required to
calibrate the ADC by correctly programming register
0x05. At any known ambient temperature the register
0x05 is programmed such to read the expected ADC
value. As an example, consider the product assem-
bly floor with an ambient temperature of 20 °C. Due to
device variation the ADC value read before calibration
can be anything between 0 °C to 40 °C. Register 0x05
is now used to tune the ADC output value to the correct
binary representation of 20 °C.
Temperature alarm
The iC-TW3 features a built-in temperature alarm sys-
tem. An alarm threshold can be specified by the user
via the TALARM(2:0) bits in register 0x03. A tempera-
ture alarm is asserted once the temperature value gen-
erated by the ADC is above the defined threshold. The
alarm is indicated by the ERR_TEMP bit set to 1 as
well as by pin NERR going low.
TALARM(2:0)
Adr 0x03; Bit 4:2
R/W
Code
temp_threshold = (TALARM(2:0) x 16) + 144
000
144 (default)
001
160
...
...
110
240
111
Alarm disabled
Table 37: Temperature alarm threshold