ATmega406 Atmel Corporation, ATmega406 Datasheet - Page 122

• 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

21.2
122
Writing to Bandgap Calibration Registers
ATmega406
Figure 21-1. Reference Circuitry
When the calibration registers are changed it will affect both the Voltage Regulator output and
BOD-level. The BOD will react quickly to new detection levels, while the regulator will adjust the
voltage more slowly, depending on the size of the external decoupling capacitor. To avoid that a
BOD-reset is issued when calibration is done, it is recommended to change the values of the
BGCC and BGCR bits stepwise, with a step size of 1, and with a hold-off time between each
step.
The hold-off time depends on the size of the voltage regulators external decoupling capacitor.
For details, see
Table 21-1.
Regulator Cap
BG Reference
10 µF
1 µF
2 µF
3 µF
4 µF
5 µF
6 µF
7 µF
8 µF
9 µF
Hold-off Times depending on CREG.
Table
21-1.
1.1V
VPTAT
Hold-off Time BGCCR
10.8 µs
12.0 µs
1.2 µs
2.4 µs
3.6 µs
4.8 µs
6.0 µs
7.2 µs
8.4 µs
9.6 µs
VREF_P
VREF_N
0.22V
VREF_GND
VREF
Hold-off Time BGCRR
12.0 µs
15.0 µs
18.0 µs
21.0 µs
24.0 µs
27.0 µs
30.0 µs
3.0 µs
6.0 µs
9.0 µs
CREF
2548E–AVR–07/06