Seeking advice for power backup circuit?

Thread Starter


Joined Feb 8, 2022
Hi everyone,

I have a primary device that consumes 6.2W on average (5.0V-1.24A). the Input voltage is supplied from a 12Vin through a Buck Regulator. I need to design a power backup circuit that can ensure if my Vin (12V) is unexpectedly lost, The V_backup will immediately supply to my device to ensure proper shutdown for about 30seconds.

I've seen super cap backup controllers like LTC3350, but it's no longer available and not able to offer enough backup energy for 30seconds. Is there any controller IC that can provide such functionalities? I find LTC4110 is quite close but not able to clearly calculate how much energy the backup source can offer.

Simplified Circuit:
12Vin --> Buck --> 5V --> Device


Joined Aug 21, 2008
1N5822 40V 3A Schottky, US 30¢ each (Qty 1) from a distributor.

I used to worry about that and sketch up switch-over circuits with lots of parts, then I realized that in many case a two Schottky diodes connected to OR a power supply's output with the output of a backup battery was a good choice. Saved a lot of parts and work designing and testing a more sophisticated switch-over circuit.