App note: Alkaline battery low-voltage indicator

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Battery low-voltage indicator made from two new comparators TSM9118 and TMS9119 from Silicon Labs. Link here (PDF)

In many battery-powered systems, a user would like to know when it is time to replace the batteries before they are completely discharged, causing the device being powered to fail completely. Alkaline batteries have an open cell voltage of about 1.5 V. As they are discharged, the voltage slowly drops. When the cell voltage reaches about 1.25 V, they have delivered about 90% of their stored energy.

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1 Comment

  1. Circuit needs an MCU control line to disable it during usage periods when load is high, otherwise it will flash too much… well, if so, might as well let the MCU keep track of the voltage.
    My Logitech mouse runs an AA battery down to about 1.00V, so 1.25V is a relatively safe trigger level.

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