Linear Technology LTC2955IDDB-1 PB On/Off Controller with Automatic Turn On (EN output) DC1836A-A DC1836A-A Fiche De Données
Codes de produits
DC1836A-A
LTC2955
9
2955f
Figure 2.ON Pin Turn-On Timing
Figure 3. Pushbutton Turn-Off Timing
OPERATION
At the end of this blanking time, the LTC2955-1 will check
that the PB pin is high. If the PB pin remains low, it will be
ignored until a high is detected on the pin. The next low
on the PB pin will initiate a turn-off sequence.
that the PB pin is high. If the PB pin remains low, it will be
ignored until a high is detected on the pin. The next low
on the PB pin will initiate a turn-off sequence.
Figure 2 shows a similar LTC2955-1 turn-on sequence
with the ON pin going high. The timing sequence is very
similar to that initiated by the pushbutton. The PGD output
follows the ON pin.
with the ON pin going high. The timing sequence is very
similar to that initiated by the pushbutton. The PGD output
follows the ON pin.
PB Pin Turn-Off Sequence
Figure 3 shows the turn-off sequence of the LTC2955-1
initiated through the PB pin. A turn-off sequence refers
to the LTC2955-1 releasing the EN output. This turns off
the voltage regulator.
initiated through the PB pin. A turn-off sequence refers
to the LTC2955-1 releasing the EN output. This turns off
the voltage regulator.
A high to low transition on PB (t
1
) starts the turn-off
sequence. In order to assert INT (interrupt output) low,
PB must stay low continuously for 32ms (t
DB(OFF)
). At
the end of the 32ms (t
2
), the INT pin is asserted low and
will stay low for at least 32ms (t
INT(MIN)
), even if the PB
pin goes high during this period (t
2
to t
4
). When the μP
receives this interrupt signal, it should start to perform
its power-down functions and assert KILL low (t
its power-down functions and assert KILL low (t
3
) once
it is done. The LTC2955-1 will then release INT and pull
EN low, thus turning off the system power, as shown with
dotted lines in Figure 3.
EN low, thus turning off the system power, as shown with
dotted lines in Figure 3.
The user can also force the system to power-down if the
μP fails to respond to the interrupt signal (KILL pin remains
μP fails to respond to the interrupt signal (KILL pin remains
16 CYCLES
KILL
TMR
t
DB(OFF)
PB
IGNORED
PB
IGNORED
PB
t
EN(LOCKOUT)
t
TMR
t
INT(MIN)
INT
EN
(LTC2955-1)
2955 F03
t
1
t
2
t
3
t
4
t
5
t
6
t
7
IGNORED
t
DB(ON)
t
KILL(ON BLANK)
ON AND KILL IGNORED
ON
t
1
t
2
t
3
2955 F02
EN
(LTC2955-1)
PGD