OR Circuit Battery Backup Solution
Backup Power Supply Solutions using an OR Circuit
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.
- Seamless switching to backup when the main power is lost
- Reduces power loss from backup batteries
|(1) Ideal Diode
Ideal diode IC, VF=20mV, 500mA (XC8110) or 1A (XC8111)
|(2) Step-up DC/DC
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
- Implementing an OR circuit using an Ideal diode. (XC8110/11) with lower VF means the leakage current loss is significantly reduced compared to a Schottky Barrier Diode.
Case (2) Apply a Step-up voltage such as 3.3V to the MCU
- Use a step-up DC/DC that supports OR connection. (XC9148C/F/M/L), please note that OR connection availability differs depending on the product and its options.
(3) Method to extend battery life with the Ship function
- Before shipping, turn on the Nch FET to cut off the supply from the backup battery. It is possible to significantly suppress the discharge from the battery until the start of use.
(4) LDO, DC/DC for main power
- LDO with reverse current prevention function prevents reverse current to the main power supply input. (XC6227).
- Alternatively, a Schottky Barrier Diode and Step-down DC/DC can also be used for an OR circuit.