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Power a 3.3V project from single Li-Ion cell: choose U1V11F3 or S7V8F3?


I have a project based on a Tinymesh radio module and a AtTiny2313 MCU, both running on 3.3V. Idle current draw will be 10-50mA. When transmitting radio packets (0-50 times a minute) the radio module draws about 400mA. I want to maximize reliability and operating time. Low voltage cutoff is not needed - uptime trumps saving the battery. I intend to power it from a single 18650 Li-Ion cell which as you know gives from 4.2 to 2.8V, i.e. a buck-boost function is needed.

Which regulator would be the best choice? Do I have to use the S7V8F3? The U1V11F3 is labeled as a Step-Up, but description says “switches to a linear down-regulation mode when the input voltage exceeds the output”.
If both can do the job, what are the tradeoffs when choosing?



You probably could use either of those regulators for your application, but I recommend the S7V8F3 step-up/step-down regulator. The U1V11F3 step-up regulator does have the down regulation mode, but since that mode is linear (not switching) it is less efficient. In addition to this, the S7V8F3 can handle more current, which means that it will run cooler.



Super. Thanks!