ATmega406 Atmel Corporation, ATmega406 Datasheet - Page 121

• Manufacturer Part Number: ATmega406
• Manufacturer: Atmel Corporation

Specifications of ATmega406

• Flash (kbytes): 40 Kbytes
• Pin Count: 48
• Max. Operating Frequency: 1 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 8
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 18
• Ext Interrupts: 4
• Usb Speed: No
• Usb Interface: No
• Twi (i2c): 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 11
• Adc Resolution (bits): 12
• Adc Speed (ksps): 1.9
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 2
• Eeprom (bytes): 512
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -30 to 85
• I/o Supply Class: 4.0 to 25
• Operating Voltage (vcc): 4.0 to 25
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 2
• Output Compare Channels: 3
• Pwm Channels: 2
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

21. Voltage Reference and Temperature Sensor
21.1
2548E–AVR–07/06
Features
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A low power band-gap reference provides ATmega406 with an accurate On-chip voltage refer-
ence V
Regulator, the V-ADC and the CC-ADC. The reference to the ADCs uses a buffer with external
decoupling capacitor to enable excellent noise performance with minimum power consumption.
The reference voltage V
ment at the current sense input pins. This configuration also enables concurrent operation of
both V-ADC and CC-ADC.
To guaranty ultra low temperature drift after factory calibration, ATmega406 features a two-step
calibration algorithm. The first step is performed at 85°C and the second at room temperature.
By default, Atmel factory calibration is performed at 85°C, and the result is stored in Flash. The
customer can easily implement the second calibration step in their test flow. This requires an
accurate input voltage and a stable room temperature. Temperature drift after this calibration is
guarantied by design and characterization to be less than 80 ppm/°C from 0°C to 60°C and 100
ppm/°C from 0°C to 85°C. The BG Calibration C Register can also be altered runtime to imple-
ment temperature compensation in software. Very high accuracy for any temperature inside the
temperature range can thus be achieved at the cost of extra calibration steps.
A lower power, less accurate voltage reference source exists. This voltage reference source is
chosen as reference for the voltage regulator whenever the band-gap voltage reference is dis-
abled. This voltage reference source is not available for the V-ADC and CC-ADC.
ATmega406 has an On-chip temperature sensor for monitoring the die temperature. A voltage
Proportional-To-Absolute-Temperature, V
connected to the multiplexer at the V-ADC input. This temperature sensor can be used for runt-
ime compensation of temperature drift in both the voltage reference and the On-chip Oscillator.
To get the absolute temperature in degrees Kelvin, the measured V
with the VPTAT factory calibration value stored in the signature row. See
Row from Software” on page 189
Accurate Voltage Reference of 1.100V
± 0.1% Accuracy After Calibration (2 mV Calibration Steps)
Temperature Drift Less than 80 ppm/°C after Calibration
Alternate Low Power Voltage Reference for Voltage Regulator
Internal Temperature Sensor
Possibility for Runtime Compensation of Temperature Drift in Both Voltage Reference and On-
chip Oscillators
External Decoupling for Optimum Noise Performance
Low Power Consumption
REF
of 1.100V. This reference voltage is used as reference for the On-chip Voltage
REF_P
/V
REF_N
for details.
to the CC-ADC is scaled to match the full scale require-
PTAT
, is generated in the voltage reference circuit and
PTAT
voltage must be scaled
”Reading the Signature
ATmega406
121