# Research a battery backup sample ## Problem environment The battery backup mode allows low power operation in sleep and persistent configuration. ## Steps to reproduce 1. Refer to the L21 [20.6.4.3 RAM Automatic Low Power Mode](https://ww1.microchip.com/downloads/en/DeviceDoc/SAM_L21_Family_DataSheet_DS60001477C.pdf) 1. Refer to the R34 **ASF SAM R34 Low Power Application** ## Expected result The battery backup mode is documented in a public sample. ## Actual result The battery backup mode is undocumented. ## Resources Rich information is available in [23.6.3 Battery Backup Power Switch](https://www.microchip.com/wwwproducts/en/ATSAML21J18B). ## Severity level This is **low priority** because project requirements do not mandate batteries.