I am thinking of using the MP5493 chip for my project.
The circuit consists of a power LED (around 11.3V, 500mA) that is powered by a rectified AC power source that behaves as a current source of 500mA.
I would like to add a 5.5V supercapacitor in parallel of the LED so that it gets charged when the power is on, and that it discharges into the LED when the power is interrupted.
I could do this using a buck converter to charge the supercap, and a boost converter (with current limit) to discharge it, but I recently came across the concept of bidirectional converters, which would greatly simplify the circuit. As I understand the datasheet, I would not use the first channel (buck) of the converter, as I only care about the features of the second channel.
Would it be an issue to not use channel 1 ? It would mean that I do not have to add L1, R1, R2, CF1 and C2 to the circuit (cf datasheet) and leave FB1 and SW1 floating (or connected to ground?)
For the MP5493, the functional block diagram shows that the internal circuits are completely independent, so you should be ok. Be wary of floating nodes that could perhaps couple noise into the circuit. Input pins should never be floating where output pins should be ok to leave floating. Since the SW and FB pins are technically inputs / have the propensity to pick up on noise, leaving these pins floating would not be advisable.
Therefore, it would be best to tie SW to GND with either a resistor or a snubber. As for FB, tie this to a known voltage that it should typically be at as stated in the datasheet.
Thank you Krishan for your reply, this is reassuring. About the MP2658 : I considered it, but it does not offer a bidirectional feature and I have very limited board space so the MP5493 would solve this issue.
I was also wondering about any current limiting feature of the second channel. There is a paragraph explaining the valley current limit protection of the buck converter in the datasheet, but it is unclear if the same applies for the buck/boost converter (channel 2). Since in my case the load is a LED, I have to know if the chip can limit the output current.
More on the operation of the supercapacitor charger is also outlined on page 16 that could also clear some things up with the following metrics above in mind:
