Battery Backup Power Supplies
OR Circuit Battery Backup Solution
Backup Power Supply Solutions using an OR Circuit
A simple back up circuit can be implemented using a Supercap (or EDLC short for Electric Double Layer Capacitor), or a lithium-titanium-oxide (LTO) battery or a standard primary cell…..
Application Examples
Backup power supply with primary coin battery.
Key requirements:
- Seamless switching to backup when the main power is lost
- Reduces power loss from backup batteries
Recommended Solution:
Backup power supply with LTO battery or supercapacitor (EDLC)
Key requirements:
- Seamless switching to backup when the main power is lost
- Efficient charging and discharging of the backup batteries or Supercaps
Recommended Solution:
|
Circuit Block |
Torex Series |
Key Features |
|---|---|---|
| (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 |
| (4) LDO | XC6227 | High speed PSRR=65dB, 700mA, true reverse current prevention |
| (5) Charging IC (LDO) | XC6240-42 | For LTO charging, 150mA, Topr=105°C with XC6242 |
| XC6230B | 2A, External adj. current limit, True reverse current prevention | |
| (6) LTO Battery Voltage Monitor | XC6140/42 | LTO battery voltage monitor, release voltage=2.475V/2.450V, Iq=104nA. For 105°C compatible LTO battery use XC6142 |
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.
(5) Charging LTO Battery or Super-cap
- The dedicated LDO XC6240/XC6242 is used to charge the LTO battery. An LDO with current limit external adjustment / reverse current prevention is the best for charging a Super-cap. (XC6230B)