SPI bus and trickle-charger — integration notes
The SPI interface keeps the pin count low — four wires (SCLK, MOSI, MISO, CS) plus the interrupt/alarm output. The trickle charger is a series diode and current-limiting resistor network that charges a backup battery or supercap from the main VCC; the datasheet shows the selectable resistor values. The square-wave output can drive a microcontroller interrupt or a status LED without an external transistor. The 96-byte NVRAM is accessed over the same SPI bus and retains data as long as the backup supply is present.
There is no NRND or last-time-buy notice on this part.