The LTC6991 is a silicon oscillator with a programmable period range of 1.024ms to 9.54 hours (29.1µHz to 977Hz), specifically intended for long duration timing events. The LTC6991 is part of the TimerBlox®family of versatile silicon timing devices.A single resistor, RSET, programs the LTC6991’s internal master oscillator frequency. The output clock period is determined by this master oscillator and an internal frequency divider, NDIV, programmable to eight settings from 1 to 221.In normal operation, the LTC6991 oscillates with a 50% duty cycle. A reset function is provided to truncate the pulse (reducing the duty cycle). The reset pin can also be used to prevent the output from oscillating.The RST and OUT pins can be configured for active-low or active-high operation using a polarity function.POL BitRST PinOutput State00Oscillating010 (reset)101 (reset)11OscillatingApplications"Heartbeat" TimersWatchdog TimersIntervalometersPeriodic "Wake-Up" CallHigh Vibration, High Acceleration EnvironmentsPortable and Battery-Powered Equipment