Sleep Power Current

Hi,

To minimise current consumption during sleep it is recommended to tie the unused port pins to VDD or VSS.

Would anyone suggest direct to vdd or vss or via a resitor? and what value?

Thanks

PeterK said:

Hi,

To minimise current consumption during sleep it is recommended to tie the unused port pins to VDD or VSS.

Would anyone suggest direct to vdd or vss or via a resitor? and what value?

Thanks

Click to expand...

I should try tying them directly to either rail, then measure the current and see which is best.

Just input pins, right? Outputs should stay what they were (boolean), and you shouldn't have any pins defined as inputs that aren't connected to something.

It's a matter of whether the signals coming into the input pins are still boolean. If it's an analog value or tristated, something may need to be done. So you need to look at what the other hardware is doing when you're going to sleep. In some cases, you could disable the other components and if that causes the other component to tristate, you can reconfigure the pin as an output. Just be sure you configure it back to an input before reenabling the other hardware.

and don't forget to turn off the brown-out fuse if you really want to minimize sleep-power consumtion. Brown-out circuitry uses about 80µA, with it turned off consmption lowers to +- 2µA, quite a diffirence...