Configurable Wake-Up Timer
with Pushbutton Control
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
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LTC2956 Timing Diagram Example
Wide Input Supply Range: 1.5V to 36V
Adjustable Wake-up Period: 250ms to 39 days
800nA Quiescent Current
Low Leakage EN Output Allows DC/DC
Converter Control (LTC2956-1)
High Voltage/EN Output Allows Circuit
Breaker Control (LTC2956-2)
Debounced Pushbutton Status Output
Pushbutton Interrupt
Adjustable Power Off Timer
±25kV ESD HBM on PB Input
12-Lead 3mm x 3mm QFN and MSOP Packages
SHORT PRESS STARTS
CYCLING TIMER
LONG PRESS STOPS
CYCLING TIMER
PB
µP SHUTS OFF
POWER
SLEEP
TIMER PERIODICALLY
ENABLES POWER
EN
tAWAKE
tSLEEP
tPERIOD
L, LT, LTC, LTM, Linear Technology and the Linear logo are
registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
2956 TA01b
Simplified State Diagram
CONFIGURED FOR
PUSHBUTTON OPERATION
OFF STATE:
EN = 0
POWER-ON
PUSHBUTTON
NOT USED
PUSHBUTTON
PRESS
SHUTDOWN MODE
(TIMER STOPPED)
PUSHBUTTON
LONG PRESS
User Actions:
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AWAKE STATE:
EN = 1
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.
Toggle SLEEP to cycle between the AWAKE and SLEEP
states in an active system.
Set ONMAX to determine the maximum awake time
before going to sleep in a passive system.
While asleep, wake up on command with a short PB
press or pulling SLEEP HIGH.
Shut down from any state with a long PB press
or long SLEEP HIGH.
TASK COMPLETE
OR
ONMAX TIMER EXPIRED
PUSHBUTTON PRESS
OR
SLEEP TIMER EXPIRED
SLEEP STATE:
EN = 0
RUN MODE
(TIMER RUNNING)
Code-Free Operation Enables Adjustment of Device Countdown Timers
Using Jumpers or Switches
Sets
Maximum Time System is ON
to Perform Routine Task
+
VBAT
VIN
LDO
VOUT
SHDN
VIN
EN
ONMAX
PBOUT
1.5nF
ONALERT
PB
GND
LTC2956-1
LONG RANGE
Sets
Pushbutton Long Press Time
to Force Timer OFF; also Sets
Timer Power Up Mode
280k
100k
VMAIN
OFFALERT
TURNED ON
TURNING OFF
µP
SLEEP
PERIOD
100k
9.76k
Sets
Internal Clock Divider
used to Calculate Wake-Up
Timer Period
Sets
Wake-Up Timer Period
from 250ms to 39 days
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