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dc2254af

DEMO MANUAL DC2254A

Dc2254a tUrret anD JUMper DeFinitions

JUMPER AND SWITCH SETTINGS

RANGE TIME PERIOD (JP2): Sets the time period between

enable signal assertions. The two available options pres-

ent on the board are 250ms and 1s. See Applications

Information in the LTC2956 data sheet and replace R11

and/or R12 if another time is desired.

AWAKE TIMER (JP1): Sets the time the enable signal stays

asserted. The onboard capacitor can be used for an awake

time of 19.9ms or an external arbitrary capacitor can be

used to set a user defined enable time. The maximum

allowed awake time is set at 13.3ms/nF.

LDO_IN (JP3): Choose the input to the onboard LT3060

regulator. It can either be set to INT to have it connected

to the VIN pin, or EXT in order to have it driven by the

LDO_IN turret. See the Operating Principles section. Only

for LED/Monitor circuitry.

SW1: This 8 pin DIP switch can be used to initialize the

part in either RUN or SHUTDOWN mode and also allows

mation in the LTC2956 data sheet for more information.

SW2: This pushbutton switch controls the input to the PB

pin. This is an active low input with a 900kΩ pull up to an

internal 3.3V regulated supply. When the pushbutton is

pressed, EN/EN pin gets asserted after an initial debounce

time of 32ms.

EXTERNAL CONNECTIONS

Signal connections are made via the row of turret posts

along the edges of the board.

GND: (3 Turrets) These turrets are connected directly to

the ground planes.

VIN: Connect a 1.6V to 36V power supply to this turret.

ONMAX: Connect a capacitor from this turret to GND if

an arbitrary awake time is desired. Use the relationship

to EXTERNAL if using this turret.

PB: This turret is already driven by the pushbutton present

on the demoboard, however if needed it can be driven by

an external signal to simulate a pushbutton press.

LDO_IN: Can be used to provide the LT3060 with power

when the LDO_IN jumper is set to EXT.

LDO_OUT: Output from the LT3060. The state of this tur-

ret can be monitored by the LED labelled “LED SUPPLY”.

DIGITAL CONNECTIONS

EN/EN:Activehigh(LTC2956-1)oractivelow(LTC2956-2)

signal. Should go active either with a debounced pushbut-

ton press or after a valid time period set by the RANGE

TIME PERIOD jumper.

ONALERT: This turret pulls low whenever the part goes

from SHUTDOWN mode to RUN mode. The signal stays

low while the EN/EN pin is asserted and it can be used as

an input to a system to request for initial boot up routine.

This turret may be left open if unused.

OFFALERT: This turret pulls low for 1 second whenever

the part goes from RUN mode to SHUTDOWN mode.

This pin can be connected to the interrupt input (with a

pullup resistor to the system supply) of a system to alert

the system before shutdown. This pin may be left open

if unused.

SLEEP: This turret is an input and is active during RUN

mode. In the Awake state, a falling edge at the SLEEP input

willde-assertEN/ENandputthesystemintotheSleepstate.

If the SLEEP input goes high during the Sleep state, the

LTC2956 reenters the Awake state and re-asserts EN/EN

to turn a system on. Holding this turret high for more

into SHUTDOWN mode. See data sheet for more details.

PBOUT: This turret follows the debounced PB input. This

turret may be left open if unused.