attiny167-esxz ATMEL Corporation, attiny167-esxz Datasheet - Page 194

• Manufacturer Part Number: attiny167-esxz
• Description: 8-bit Avr 8-bit Microcontroller Microcontroller With 16k Bytes In-system Programmable Flash And Lin Controller
• Manufacturer: ATMEL Corporation

17.9.1
17.9.2
17.10 Internal Voltage Reference Output
194
ATtiny167
User Calibration
Manufacturing Calibration
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 17-2.
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
page 212.
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 = 3V and with ADC in internal Vref (1.1V) mode.
The temperature in Celsius degrees can be calculated utilizing the formula:
Where:
The internal voltage reference is output on XREF pin as described in
turned on
XREF pin may be necessary.
Temperature / °C
a. ADCH & ADCL are the ADC data registers,
b. TSGAIN is the temperature sensor gain (constant 1, or unsigned fixed point number,
c. TSOFFSET is the temperature sensor offset correction term (2. complement signed
194. The voltage sensitivity is approximately 1 mV/
Voltage / mV
0x80 = decimal 1.0)
byte)
(See Section “6.2.1” on page
T = { [ (ADCH << 8) | ADCL ] *TSGAIN } + TSOFFSET-273
Temperature vs. Sensor Output Voltage (Typical Case)
Table 17-2 on page 194
T = { [ (ADCH << 8) | ADCL ] - T
247 mV
-40 °C
51.). Addition of an external filter capacitor (5 - 10 nF) on
are typical values. However, due to the process
°
314 mv
C and the accuracy of the temperature
+25 °C
OS
} / k
Table 17-3
See Section “20.2.4” on
OS
7728A–AUTO–07/08
382 mV
+85 °C
is the temper-
Table 17-2 on
if the ADC is