LTC2954

6

2954f



PB (Pin 2/Pin 3): Push Button Input. Connecting PB to

ground through a momentary switch provides On/Off

control via the EN/EN and INT outputs. An internal 100k

pull-up resistor connects to an internal 1.9V bias voltage.

The rugged PB input withstands ±10kV ESD HBM and

can be pulled up to 26.4V externally without consuming

extra current.

ONT (Pin 3/Pin 2): Turn On Time Input. Placing an external

capacitor to ground determines the additional time (6.4

seconds/µF) the PB pin must be held low before the enable

output is asserted. Floating this pin results in a default turn

on debounce time of 32ms.

GND (Pin 4/Pin 1): Device Ground.



INT(Pin5/Pin8):OpenDrainInterruptOutput.Afterapush

interrupts the system (µP) by asserting the INT pin low.

The µP would perform power down and housekeeping

tasks and then assert the KILL pin low, thus releasing the

enable output. The INT pulse width is a minimum of 32ms

and stays low as long as PB is asserted. If PB is asserted

are immediately released.

EN (LTC2954-1, Pin 6/Pin 7): Open Drain Enable Output.

Thispinisintendedtoenablesystempower.ENisasserted

released low if: a) KILL is not driven high (by μP) within

512ms of the initial valid PB power turn-on event, b) KILL

is driven low during normal operation, c) PB is pressed

operating range for this low leakage pin is 0V to 26.4V.



EN (LTC2954-2, Pin 6/Pin 7): Open Drain Enable Bar

Output. This pin is intended to enable system power. EN is



ENreleaseshighif:a)KILLisnotdrivenhigh(byμP)within

512ms of the initial valid PB power turn-on event, b) KILL

is driven low during normal operation, c) PB is pressed

The operating range of this pin is 0V to 26.4V.

PDT (Pin 7/Pin 6): Power Down Time Input. A capacitor

to ground determines the additional time (6.4 seconds/µF)

that the push button must be held low before immediately

releasing the EN/EN and INT outputs. Floating this pin

results in a push button power down time of 64ms.



KILL (Pin 8/Pin 5): Kill Input. Forcing KILL low releases the

enable output. During system turn on, this pin is blanked

system to pull KILL high. This pin has an accurate 0.6V

threshold and can be used as a voltage monitor input.

Exposed Pad (Pin 9 DFN Only): Exposed Pad may be left

open or connected to device ground.

(TSOT-23/DFN)

PI FU CTIO S