ata6616 ATMEL Corporation, ata6616 Datasheet - Page 228

• Manufacturer Part Number: ata6616
• Description: Microcontroller With Lin Transceiver, 5v Regulator And Watchdog
• Manufacturer: ATMEL Corporation

4.18.9
4.18.9.1
4.18.9.2
228
ATA6616/ATA6617 [Preliminary]
Temperature Measurement
User Calibration
Manufacturing Calibration
The temperature measurement is based on an on-chip temperature sensor that is coupled to a
single ended. MUX[4..0] bits in ADMUX register enables the temperature sensor. The internal
1.1V voltage reference must also be selected for the ADC voltage reference source in the tem-
perature sensor measurement. When the temperature sensor is enabled, the ADC converter
can be used in single conversion mode to measure the voltage over the temperature sensor.
The measured voltage has a linear relationship to the temperature as described in
page
measurement is ± 10°C after bandgap calibration.
Table 4-55.
The values described in
variation the temperature sensor output voltage varies from one chip to another. To be capable
of achieving more accurate results, the temperature measurement can be calibrated in the appli-
cation software.
The software calibration requires that a calibration value is measured and stored in a register or
EEPROM for each chip. The software calibration can be done utilizing the formula:
where ADCH & ADCL are the ADC data registers, k is a fixed coefficient and T
ature sensor offset value determined and stored into EEPROM.
One can also use the calibration values available in the signature row (see
“Reading the Signature Row from Software” on page
The calibration values are determined from values measured during test at room temperature
which is approximatively +25°C and during test at hot temperature which is approximatively
+125°C. Calibration measures are done at Vcc = 5V and with ADC in internal Vref (1.1V) mode.
The temperature in Celsius degrees can be calculated utilizing the formula:
Where:
T = { [ (ADCH << 8) | ADCL ] - T
T = { [ (ADCH << 8) | ADCL ] *TSGAIN } + TSOFFSET-273
Temperature/ C
228. The voltage sensitivity is approximately 1 mV/ C and the accuracy of the temperature
a. ADCH & ADCL are the ADC data registers,
b. TSGAIN is the temperature sensor gain (constant 1, or unsigned fixed point num-
c. TSOFFSET is the temperature sensor offset correction term (2. complement
Voltage/mV
ber, 0x80 = decimal 1.0)
signed byte)
Temperature versus Sensor Output Voltage (Typical Case)
Table 4-55 on page 228
247 mV
-40 C
OS
} / k
DRAFT
are typical values. However, due to the process
246).
+25 C
314 mv
Section 4.21.2.4
OS
9132A–AUTO–10/08
382 mV
+85 C
Table 4-55 on
is the temper-