ATmega406 Atmel Corporation, ATmega406 Datasheet - Page 108

• 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

108
ATmega406
Figure 18-3. Accumulation Current Conversion
While the CC-ADC is converting, the CPU can enter sleep mode and wait for an interrupt from
the Accumulate Current conversion. After adding the new Accumulate Current value for Cou-
lomb Counting, the CPU can go back to sleep again. This reduces the CPU workload, and
allows more time spent in low power modes, reducing power consumption. The CC-ADC can
generate an interrupt if the result of an Instantaneous Current conversion is greater than a pro-
grammable threshold. This allows the detection of a Regular Current condition. This function is
available in Active mode and all sleep modes except Power-down and Power-off mode. This
allows an ultra-low power operation in Power-save, where the CC-ADC can be configured to
enter a Regular Current detection mode with a programmable current sampling interval. By set-
ting the CADSE bit in CADCSRA, the Coulomb Counter will repeatedly do one Instantaneous
Current conversion, before it is being turned off for a timing interval specified by the CADSI bits
in CADCSRA. This allows operating the Regular Current detection while keeping the Coulomb
Counter off most of the time.
The Coulomb Counter is halted in Power-down mode. In this mode, time measurements and the
battery self-discharge characteristics should be used to estimate the charge flow. When waking
up from Power-down mode, the CC-ADC will automatically resume continuous operation.
The CC-ADC is enabled by setting the CC-ADC Enable bit, CADEN, in CADCSRA. Note that the
bandgap voltage reference must be enabled separately, see
Register” on page
The CC-ADC will not consume power when CADEN is cleared. It is therefore recommended to
switch off the CC-ADC whenever the Coulomb Counter or Regular Current Detection functions
are not used. The CC-ADC is automatically disabled in Power-down and Power-off mode.
After the CC-ADC is enabled, either by setting the CADEN bit or leaving Power-down with
CADEN already set, the first four conversions do not contain useful data and should be ignored.
This also applies after clearing the CADSE bit.
In-system offset voltage for the CC-ADC is typically in the range 0 - 100 µV. To compensate for
this offset error, a CC-ADC offset value should be stored in EEPROM and subtracted from each
Accumulate Current conversions before the resulting value is added for Coloumb Counting. The
CC-ADC offset value can be found by performing a CC-ADC conversion at typical temperature
with zero current flowing through R
When the battery is not used or the current level stays very low for a long time, it is recom-
mended to estimate the charge flow instead of using the CC-ADC for Coloumb Counting. The
Accumulation Interrupt
Accumulation Data
Read byte 2
Read byte 1
Read byte 3
Read byte 4
Enable
123.
Setting of Digital Filters
SENSE
.
125, 250, 500,
or 1000 ms
DATA1
125, 250, 500,
or 1000 ms
DATA2
”BGCCR – Bandgap Calibration C
250, 500, 1000,
or 2000 ms
DATA 3
DATA5
2548E–AVR–07/06