This topic was migrated from the BotBlox ticketing system after being summarized and anonymized.
Q: We were wondering if the UbiSwitch Baseboard can power be powered at 5V or it creates problems.
Short Answer:
Powering it at 5V is ok, but it is quite close to the minimum input voltage of 4.5V. So if it’s powered from 5V, it needs to be a clean 5V that will not drop below 4.5V, even momentarily. Powering it at 5V also increases the current supply needs of the board.
Detailed Answer:
The absolute minimum input voltage for the onboard DC/DC regulators is 4.5 V. The concern with powering UbiSwitch from a 5 V rail is that there is very little margin. If the input voltage temporarily drops below 4.5 V, UbiSwitch may reset.
For example, if another device sharing the same 5 V rail draws a short high-current pulse, this could cause the 5 V rail to sag below the regulator minimum. For this reason, if UbiSwitch is powered from 5 V, the supply needs to be well regulated, clean, and able to maintain voltage under transient load.
There is also a current consideration. If UbiSwitch requires around 7 W, then at 5 V the supply must provide approximately 1.4 A. At 20 V, the same 7 W load would require only around 0.35 A. Therefore, when using a 5 V supply, it is important to confirm that the supply and cabling can deliver the required current without excessive voltage drop.
SFP modules can also increase the total power draw. Depending on the module, each SFP may add up to around 3 W, which further increases the current required from a 5 V supply.
So there is nothing fundamentally wrong with running UbiSwitch from 5 V. The key requirements are that the 5 V supply is clean, well regulated, and capable of supplying the required current for UbiSwitch plus any installed SFP modules. We recommend 8 V or higher simply to provide comfortable margin above the 4.5 V absolute minimum and reduce the risk of resets caused by voltage dips.