3
dc1836af
DEMO MANUAL DC1836A
operating principles
Figure 2.
PB
going Low For 46.1ms, and En Pulling High,
Showing a Proper Turn-On Sequence
Figure 3.
PB
going Low for 28.6ms, and
EN
remaining High,
Showing Too Short of a
PB
Pulse to Properly Activate the Enable Pin
Figure 4. A Turn-On Sequence Where V
in
and On Activate En, as Opposed to PB.
notice the 924ms Delay Between V
in
going High and En Activating
Connect a 1.6V to 36V power supply to VIN. If VIN is
less than 5.5V, set the LDO_IN jumper to EXTERNAL and
connect a 5.5V to 36V supply to the LDO_IN turret. The
LTC2955 will still operate with no power applied to LDO_IN,
but monitor LEDs will not function.
On the DC1836A, a pushbutton switch shorts the
PB
pin
to ground which in turn sets the
EN
pin low (DC1836A-B)
or the EN pin high (DC1836A-A). Shorting
PB
to ground
a second time and holding (duration depending on the
TMR_PERIOD jumper) subsequently de-asserts the
EN/
EN
pin. The EN/
EN
pin is unobtrusively monitored by
the LT6700 comparator.
An internal 512ms timer blanks (ignores) the
KILL
signal
during system power-up. This allows sufficient time for
the DC/DC converter and a controller to perform power-
up tasks.
A high to low transition on
PB
starts the turn-off sequence.
In order to assert
INT
low,
PB
must stay low continuously
for 32ms. Users can also force the system to power down
by holding the pushbutton down for a long period; this
period is set using the TMR_PERIOD jumper on the board.
After the EN/
EN
pin has been released, the LTC2955 starts
a one second lockout time. During this lockout time, the
PB
and ON inputs are ignored—this is meant to allow the
voltage regulator to turn off and for its output to decay to 0V.
dc1836a F04
EN
PB
V
IN
0N
dc1836a F03
PB
EN
PB
EN
dc1836a F02
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