Yes, they're called low-power (or nano-power) system timers. Some also incorporate watchdog timer functionality. These chips turn on power to the main CPU based on some given interval. TI has a few that consume ~30nA (@2.5V), like the TPL5100.
This is when the MCU itself you're using doesn't have this functionality of if it's still consuming too much power. MCUs like the ATMega368(PU) consume ~100nA in their deepest sleep states, so it can be a rather drastic reduction in some cases.
This is when the MCU itself you're using doesn't have this functionality of if it's still consuming too much power. MCUs like the ATMega368(PU) consume ~100nA in their deepest sleep states, so it can be a rather drastic reduction in some cases.