LTC2956 Schematic for the Cat Feeder Unreminder

Based on my testing of the evaluation board, this is the schematic for the LTC2956 I am using in the Cat Feeder Unreminder.

The resistor from RANGE to LONG pin is set to 100K ohms. This is specified in the datasheet.

To set the actual time for the timer to activate the EN pin (t PERIOD), You need to first select the range resistance from the chart below. In my case I want to activate every 22hrs. 162K ohms is the resistor I chose which sets NRANGE to 262,144.

To calculate the period resistor, this is the formula provided by in the datasheet.


For 22hrs, tPERIOD becomes 22 x 60 x 60 x 1000 = 79,200,000. This gives an R PERIOD of 120,849.609 ohms. I picked a 121K ohm resistor.

To send the device into the sleep state, I tied the SLEEP signal through a switch to VCC (3.3V). This brings SLEEP high on button press. When the button is released, SLEEP has a falling edge which is what the LTC2956 is looking for to send it into the sleep state.