ATmega324P datasheet(53/377 Pages) ATMEL

53 / 377 page

7674F–AVR–09/09

ATmega164P/324P/644P

Figure 9-4.

Watchdog Reset During Operation

9.1

Internal Voltage Reference

ATmega164P/324P/644P features an internal bandgap reference. This reference is used for

Brown-out Detection, and it can be used as an input to the Analog Comparator or the ADC.

9.1.1

Voltage Reference Enable Signals and Start-up Time

The voltage reference has a start-up time that may influence the way it should be used. The

start-up time is given in “System and Reset Characteristics” on page 332. To save power, the

reference is not always turned on. The reference is on during the following situations:

When the BOD is enabled (by programming the BODLEVEL [2:0] Fuse).

When the bandgap reference is connected to the Analog Comparator (by setting the

ACBG bit in ACSR).

When the ADC is enabled.

Thus, when the BOD is not enabled, after setting the ACBG bit or enabling the ADC, the user

must always allow the reference to start up before the output from the Analog Comparator or

ADC is used. To reduce power consumption in Power-down mode, the user can avoid the three

conditions above to ensure that the reference is turned off before entering Power-down mode.

ATmega324P Datasheet(PDF) 53 Page - ATMEL Corporation