Battery backup circuits are circuit types that immediately shift the load to the battery when there’s no main supply. However, if there is a main supply, the load shifts to the power supply and the backup battery is isolated or disconnected from the system.
A simple back up circuit can easily be implemented using a standard primary cell and depending on VBAT level and the required system Voltage there are different solutions to consider as illustrated in the article below
Backup power supply with primary coin battery.
|(1) Ideal Diode||XC8110/11||
Ideal diode IC, VF=20mV, 500mA (XC8110) or 1A (XC8111)
|(2) Step-up DC/DC||XC9148||
1.2MHz/ or 3MHz, 750mA @ 3.3V→5V. For OR connection
N-channel MOSFET 20V, 0.3A for Ship-Mode Function
High speed PSRR=65dB, 700mA, true reverse current prevention
OR Circuit Examples
Case (1) Apply backup battery voltage directly to the MCU
Case (2) Apply a Step-up voltage such as 3.3V to the MCU
(3) Method to extend battery life with the Ship function
(4) LDO, DC/DC for main power