Date
03/03/2015
PDF
The LTC2956 wake-up timer
Linear Technology introduced the LTC2956, a wake-up timer with pushbutton control that manages 1.5V to 36V system power. Using microcontrollers or real-time clocks to track timing overcomplicates many designs. Electronic devices used to perform routine tasks, such as monitoring human body temperature, monitoring strain in a bridge, or capturing images, benefit from adjustable timing options without the need to program devices or upgrade firmware. The LTC2956 periodically “wakes up” and turns on a system to perform these tasks, then turns the system off to conserve power. While “sleeping” the LTC2956 sips only 800nA of quiescent current from a battery or rail. The wake-up period is resistor-adjustable from 250ms to 39 days, requires no code, and enables users to easily set device countdown timers via jumpers or switches.
The ease of use, wide operating range, and nanocurrent consumption of the LTC2956 are ideal for single-cell, multicell and high voltage devices, including intervalometers, which are used in time-lapse photography or military countermeasure applications, as well as “heartbeat” timers. A ±25kV ESD protected pushbutton input starts the wake-up timer, allowing users to issue a short pushbutton press to override the timer for early wake-up or to issue a long pushbutton press to stop the timer completely and put the entire system to sleep with 300nA IQ. The LTC2956 can also be configured to power up with the wake-up timer running automatically without the need of a pushbutton press. An adjustable watchdog timer allows users to limit the time a system is “awake” to prevent faulty microcontrollers or software from keeping a system on indefinitely until battery power is drained.
The LTC2956 is now available in both positive (LTC2956-1) and negative (LTC2956-2) enable polarities, and in
12-lead 3mm x 3mm DFN or 12-lead MSOP packages. Offered over the commercial and industrial temperature ranges, the LTC2956 is priced starting at $1.98 each in 1000-piece quantities.
