AT90USB646 datasheet(425/434 Pages) ATMEL

425 / 434 page

425

7593A–AVR–02/06

AT90USB64/128

35. Errata

The revision letter in this section refers to the revision of the AT90USB64/128 device.

35.1 Rev A

• VBUS residual level

• Spike on TWI pins when TWI is enabled

• High current consumption in sleep mode

• Async timer interrupt wake up from sleep generate multiple interrupts

VBUS residual level

In USB device and host mode, once a 5V level has been detected to the VBUS pad, a resid-

ual level (about 3V) can be measured on the VBUS pin.

Problem fix/workaround

None.

3. Spike on TWI pins when TWI is enabled

100 ns negative spike occurs on SDA and SCL pins when TWI is enabled.

Problem Fix/workaround

No known workaround, enable AT90USB64/128 TWI first versus the others nodes of the

TWI network.

2. High current consumption in sleep mode

If a pending interrupt cannot wake the part up from the selected mode, the current consump-

tion will increase during sleep when executing the SLEEP instruction directly after a SEI

instruction.

Problem Fix/workaround

Before entering sleep, interrupts not used to wake up the part from the sleep mode should

be disabled.

1. Asynchonous timer interrupt wake up from sleep generates multiple interrupts

If the cpu core is in sleep and wakeups 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.

AT90USB646 Datasheet(PDF) 425 Page - ATMEL Corporation