The LTC®2956 Wake-Up Timer provides a periodic on/off signal, waking up a system to perform routine tasks (such as measuring a sensor or capturing images) while keeping it off most of the time to save power. While “sleeping,” the LTC2956 sips only 800nA of quiescent current from a battery or rail.

An optional pushbutton starts the timer, and allows users to override the timer for early wake-up or give a long pushbutton press to stop the timer completely and shut down the entire system. The LTC2956 can also be configured to run automatically without a pushbutton. The wake-up period is resistor-adjustable from 250ms to 39 days, requires no software code and allows easy timer configuration via jumpers or switches.

Features n Wide Input Supply Range: 1.5V to 36V n Adjustable Wake-up Period: 250ms to 39 days n 800nA Quiescent Current n Low Leakage EN Output Allows DC/DC

Converter Control (LTC2956-1) n High Voltage/EN Output Allows Circuit

Breaker Control (LTC2956-2) n Debounced Pushbutton Status Output n Pushbutton Interrupt n Adjustable Power Off Timer n ±25kV ESD HBM on PB Input n 12-Lead 3mm x 3mm QFN and MSOP Packages

Configurable Wake-Up Timer with Pushbutton Control

PB

SLEEP

EN

2956 TA01btSLEEPtAWAKE

tPERIOD

SHORT PRESS STARTSCYCLING TIMER

LONG PRESS STOPSCYCLING TIMER

µP SHUTS OFFPOWER

TIMER PERIODICALLYENABLES POWER

LTC2956 Timing Diagram Example

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AWAKE STATE:EN = 1

RUN MODE(TIMER RUNNING)

POWER-ON

PUSHBUTTON PRESSORSLEEP TIMER EXPIRED

TASK COMPLETE OR

ONMAX TIMER EXPIRED

PUSHBUTTONPRESS

CONFIGURED FORPUSHBUTTON OPERATION

PUSHBUTTONNOT USED

SLEEP STATE:EN = 0

OFF STATE:EN = 0

SHUTDOWN MODE(TIMER STOPPED)

PUSHBUTTONLONG PRESS

Simplified State Diagram

Code-Free Operation Enables Adjustment of Device Countdown Timers Using Jumpers or Switches

LTC2956-1

PBOUT

SLEEP

OFFALERT

ONALERTTURNING OFF

TURNED ON

PBGND

ONMAX

VBAT

ENVIN

RANGE

VOUTVIN

LDO

SHDN

LONG

VMAIN

1.5nF

µP

100k280k 9.76k

PERIOD

100k

+

User Actions: n Power up in RUN mode to instantly perform the system

task and start the timer, or in SHUTDOWN mode where a PB press starts the task and timer.

n Toggle SLEEP to cycle between the AWAKE and SLEEP states in an active system.

n Set ONMAX to determine the maximum awake time before going to sleep in a passive system.

n While asleep, wake up on command with a short PB press or pulling SLEEP HIGH.

n Shut down from any state with a long PB press or long SLEEP HIGH.

Sets Maximum Time System is ON

to Perform Routine Task

Sets Internal Clock Divider

used to Calculate Wake-Up Timer Period

Sets Wake-Up Timer Period from 250ms to 39 days

Sets Pushbutton Long Press Time to Force Timer OFF; also Sets

Timer Power Up Mode

0115

www.linear.com/2956 n 1-800-4-LINEAR