466130 Datasheet, PDF (28/36 Pages) ATMEL Corporation – 8-bit Microcontroller with 64/128K Bytes of ISP Flash

If the CPU core is in sleep and wakes-up from an asynchronous timer interrupt and then go
back in sleep again it may wake up multiple times.
Problem Fix/workaround
A software workaround is to wait with performing the sleep instruction until
TCNT2>OCR2+1.
28 ATmega32U6/AT90USB64/128
7593JS–AVR–03/09