LTC2954
U U
U
PI FU CTIO S (TSOT-23/DFN)
released low if: a) KILL is not driven high (by μP) within
512ms of the initial valid PB power turn-on event, b) KILL
is driven low during normal operation, c) PB is pressed
V (Pin 1/Pin 4): Power Supply Input: 2.7V to 26.4V.
IN
PB (Pin 2/Pin 3): Push Button Input. Connecting PB to
ground through a momentary switch provides On/Off
control via the EN/EN and INT outputs. An internal 100k
pull-up resistor connects to an internal 1.9V bias voltage.
The rugged PB input withstands ±10kV ESD HBM and
can be pulled up to 26.4V externally without consuming
extra current.
and held low (t
+ t ) during normal operation. The
PD, Min PDT
operating range for this low leakage pin is 0V to 26.4V.
EN (LTC2954-2, Pin 6/Pin 7): Open Drain Enable Bar
Output. This pin is intended to enable system power. EN is
asserted low after a valid PB turn-on event (t + t ).
DB, ON ONT
ENreleaseshighif:a)KILLisnotdrivenhigh(byμP)within
512ms of the initial valid PB power turn-on event, b) KILL
is driven low during normal operation, c) PB is pressed
ONT(Pin3/Pin2):TurnOnTimeInput. Placinganexternal
capacitor to ground determines the additional time (6.4
seconds/µF)thePBpinmustbeheldlowbeforetheenable
outputisasserted. Floatingthispinresultsinadefaultturn
on debounce time of 32ms.
and held low (t
+ t ) during normal operation.
PDT
PD, Min
The operating range of this pin is 0V to 26.4V.
PDT (Pin 7/Pin 6): Power Down Time Input. A capacitor
togrounddeterminestheadditionaltime(6.4seconds/µF)
GND (Pin 4/Pin 1): Device Ground.
INT(Pin5/Pin8):OpenDrainInterruptOutput.Afterapush that the push button must be held low before immediately
button turn off event is detected (t
), the LTC2954 releasing the EN/EN and INT outputs. Floating this pin
DB,OFF
interrupts the system (µP) by asserting the INT pin low. results in a push button power down time of 64ms.
The µP would perform power down and housekeeping
KILL(Pin8/Pin5):KillInput.ForcingKILLlowreleasesthe
tasks and then assert the KILL pin low, thus releasing the
enable output. During system turn on, this pin is blanked
enable output. The INT pulse width is a minimum of 32ms
by a 512ms internal timer (t
system to pull KILL high. This pin has an accurate 0.6V
threshold and can be used as a voltage monitor input.
) to allow the
KILL, ON BLANK
and stays low as long as PB is asserted. If PB is asserted
for longer than t
+ t , the INT and EN/EN outputs
PDT
PD,Min
are immediately released.
Exposed Pad (Pin 9 DFN Only): Exposed Pad may be left
open or connected to device ground.
EN (LTC2954-1, Pin 6/Pin 7): Open Drain Enable Output.
Thispinisintendedtoenablesystempower.ENisasserted
high after a valid PB turn on event (t
+ t ). EN is
ONT
DB,ON
2954f
6