Micropower wake-up timer for power-sensitive applications up to 36 V

March 04, 2015 // By Graham Prophet
Featuring pushbutton control, LTC2956 it a wake-up timer that manages 1.5V to 36V system power, that is presented as offering an improved solution compared to using microcontrollers or real-time clocks to track timing, which, Linear Technology says, overcomplicates designs.

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 needs only 800 nA of quiescent current from a battery or rail. The wake-up period is resistor-adjustable from 250 msec to 39 days, requires no code, and enables users to set device countdown timers via jumpers or switches.

The ease of use, wide operating range, and nanocurrent consumption of the LTC2956 are suitable 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 ±25 kV 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 300 nA 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 available in both positive (LTC2956-1) and negative (LTC2956-2) enable polarities, and in 12-lead 3 x 3 mm DFN or 12-lead MSOP packages. Operating over the commercial and industrial temperature ranges, the LTC2956 is priced starting at $1.98 (1000).

Linear Technology; www.linear.com/pushbutton