Datasheet

Data Sheet ADM1186
Rev. B | Page 3 of 28
During a power-up sequence, the state machine enables each
power supply in turn. The supply output voltage is monitored to
determine whether it rises above the UV threshold level within
a user defined duration called the blanking time. If a supply
rises above the UV threshold, the next enable output in the
sequence is turned on. In addition to the blanking time, the
user can also define a sequence time delay before each enable
output is turned on.
The ADM1186-1 provides an open-drain pin, SEQ_DONE,
that is asserted high to provide an indication that a power-up
sequence is complete. The SEQ_DONE pin allows multiple
cascaded ADM1186-1 devices to perform controlled power-up
and power-down sequences.
During a power-down sequence, the enable outputs turn off
in reverse order. The same sequence time delays used during
the power-up sequence are also used during the power-down
sequence as each enable output is turned off; no blanking time
is used during a power-down sequence. At the end of a power-
down sequence, the SEQ_DONE pin is brought low.
During sequencing and when powered up, the state machine
continuously monitors the part for any fault conditions. Faults
include a UV condition on any of the inputs or an unexpected
control input. Any fault causes the state machine to enter a fault
handler, which immediately turns off all enable outputs and
then ensures that the device is ready to start a new power-up
sequence.
The ADM1186-1 has a bidirectional pin,
FAULT
, that facilitates
fault handling when using multiple devices. If an ADM1186-1
experiences a fault condition, the
FAULT
pin is driven low,
causing other connected ADM1186-1 devices to enter their own
fault handling states.
The ADM1186-1 is available in a 20-lead QSOP package, and
the ADM1186-2 is available in a 16-lead QSOP package.
07153-004
POWER-DOWN
DONE
WAIT START
FAULT HANDLER
SEQUENCE
SUPPLY 1 ON
SEQUENCE
SUPPLY 1 OFF
SEQUENCE
SUPPLY 2 ON
SEQUENCE
SUPPLY 2 OFF
SEQUENCE
SUPPLY 3 OFF
SEQUENCE
SUPPLY 4 OFF
SEQUENCE
SUPPLY 3 ON
SEQUENCE
SUPPLY 4 ON
POWER-UP DONE
SEQUENCE UP
TRIGGER
SEQUENCE DOWN TRIGGER
FAULT CONDITION OCCURS
IN ANY STATE
Figure 2. Simplified State Machine Diagram