LTC4055 datasheet(6/16 Pages) LINER

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LTC2951

2951f

VIN (Pin 1/Pin 4): Power Supply Input: 2.7V to 26.4V.

⎯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 pin. An internal 100k pull-up resis-

tor connects to an internal 1.9V bias voltage. The rugged

⎯P⎯B input can be pulled up to 26.4V externally without

consuming extra current.

KILLT (Pin 3/Pin 2): Additional, Adjustable ⎯K⎯I⎯L⎯L Turn Off

Delay Input (t⎯K⎯I⎯L⎯L, OFF DELAY, ADDITIONAL). A capacitor to

ground provides additional delay time (beyond the internal

default 128ms, t⎯K⎯I⎯L⎯L, OFF DELAY) from ⎯I⎯N⎯T falling to the

automatic release of the enable output. The ⎯K⎯I⎯L⎯L turn off

delay feature ensures the release of the enable pin under

system fault conditions, such as the µP not responding

to the LTC2951 interrupt signal (⎯I⎯N⎯T low).

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

⎯I⎯N⎯T (Pin 5/Pin 8): Open Drain Interrupt Output. After a

push button turn-off event is detected (tDB, OFF + tOFFT),

the LTC2951 interrupts the system (µP) by bringing the

⎯I⎯N⎯T pin low. Once the system ﬁnishes its power down

and housekeeping tasks, it sets ⎯K⎯I⎯L⎯L low, which in turn

releases the enable output. If at the end of the power

down timer period (t⎯K⎯I⎯L⎯L, OFF DELAY + t⎯K⎯I⎯L⎯L, OFF DELAY, AD-

DITIONAL) ⎯K⎯I⎯L⎯L is still high, the enable output is released

immediately. ⎯I⎯N⎯T may optionally be tied to ⎯K⎯I⎯L⎯L to release

the enable output immediately after the turn-off event has

been detected (⎯I⎯N⎯T low).

EN (LTC2951-1, Pin 6/Pin 7): Open Drain Enable Output.

This pin is intended to enable system power. EN goes high

after a valid ⎯P⎯B turn on event (tDB, ON). EN goes low if: a)

⎯K⎯I⎯L⎯L is not driven high within 512ms of the initial valid ⎯P⎯B

power turn-on event, b) ⎯K⎯I⎯L⎯L is driven low during normal

operation, or c) a second valid ⎯P⎯B event (power turn-off)

is detected. The operating range for this pin is 0V to 10V.

A 100k pull-up is recommended if not available in the

DC/DC converter.

⎯⎯E⎯N (LTC2951-2, Pin 6/Pin 7): Open Drain Enable Output.

This pin is intended to enable system power. ⎯E⎯N is asserted

low after a valid ⎯P⎯B turn-on event (tDB, ON). ⎯E⎯N releases

high if: a) ⎯K⎯I⎯L⎯L is not driven high within 512ms of the

initial valid ⎯P⎯B power turn-on event, b) ⎯K⎯I⎯L⎯L is driven low

during normal operation, or c) a second valid ⎯P⎯B event

(power turn-off) is detected. The operating range of this

pin is 0V to 10V. A 100k pull-up is recommended if not

available in the DC/DC converter.

OFFT (Pin 7/Pin 6): Additional Adjustable Turn Off Time

Input (tOFFT). A capacitor to ground determines the ad-

ditional time (beyond the internal default 32ms, tDB, OFF)

that the ⎯P⎯B pin must be held low before initiating a power

down sequence (⎯I⎯N⎯T falling). Floating this pin results in a

default turn off debounce time of 32ms.

⎯K⎯I⎯L⎯L (Pin 8/Pin 5): ⎯K⎯I⎯L⎯L Input. Forcing ⎯K⎯I⎯L⎯L low releases

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

by a 512ms internal timer (t⎯K⎯I⎯L⎯L, ON BLANK) to allow the

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): Exposed Pad may be left open or

connected to device ground.

(TSOT-23/DFN)

PI FU CTIO S

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