SouthernAtHeart:
5 volt system.
An atmega328P-AU, DS3234, & h-bridge (Si9986)My atmega will be sleeping, waiting for the interrupt from the DS3234 timer. DS3234 will have Vcc cut off from an Arduino pin, so it runs on Vbatt. But if I'm reading the datasheet correctly on the Si9886, it uses 300 uA in standby mode.
300uA maximum, but more like 65uA typical @ Vdd=5V judging from page 3 of the datasheet.
Low-side switching to turn the power supply to the H-bridge off using an N-channel mosfet is OK provided you set INA and INB high first. Similarly, turn the mosfet on before you set the pins driving INA and INB to be outputs. It's slightly better to put the 10K resistor to ground on the other side of the 330 ohm resistor unless there is a connector involved, that way the mosfet gate gets the full ~5V drive from the atmega328p instead of ~97% of it.