Other Parts Discussed in Thread: TPS2216
Tool/software:
I am designing very low power sensor where most of the electronics has no power at all (ie. I am not even using EN/ signals).
Most of the time, the MCU is powered directly by a Lithium Ion battery, where +BATT may range from 2.8 up to 4.2V.
Only when it needs to talk to other devices, one dedicated GPIO pin (3V3_EN) starts a regulated 3.3V LDO, which in turn bring power to the I2C/SPI 3V3 devices.
Now the interesting thing : I want to avoid the need for level shifters.
So I plan on using a TPS2116 to switch the MCU power itself from +BATT to this 3.3V rail before I talk to the sensors.
So when 3V3 is available VOUT shall be 3V3 ; else it should be +BATT (the +BATT may be smaller or larger than 3V3).
I suspect I need to use the manual mode of the TPS2216, but is the schematics below the proper way to do ?
A) I fear that the small power gap between 3V3_EN and stabilized 3.3V might reset my MCU when +BATT is very low (well, the MCU needs 1.8V minimum).
B) I could add an RC delay on 3V3_EN to switch to 3.3V after the 3.3V is stable enough. Or could I just tie PR1 to VIN1 ? Possibly with a resistor divider ?
C) I also suspect I could still use automatic mode with some clever trick on PR1
Thanks
