SMS66
Preliminary Information
VDD (+2.7V to +5.5V)
or 12VIN ( +8V to +15V)
2.7V
2.5V
2.0V
1.8V
1.5V
t
DPONA
t
DPONB
RST#
t
DPONC
t
DPOND
t
DPONE
t
DPONF
t
PRTO
Figure 2 – Example Power Supply Sequencing and System Start-up Initialization using the SMS66.
Any order of supply sequencing can be applied using the SMS66 with very accurate monitoring and
supervisory functions.
GENERAL DESCRIPTION
The SMS66 is a highly integrated power supply
controller, monitor and sequencer. It has the ability to
control, monitor and sequence up to six power
supplies. Also, the SMS66 can monitor the VDD input,
the 12V input, two general-purpose analog inputs and
the internal temperature sensor. The SMS66 has
three operating modes: Power-on sequencing mode,
monitor mode, and Power-off sequencing mode.
Power-on sequencing can be initiated via the
PWR_ON/OFF pin or I
2
C control. In this mode, the
SMS66 will sequence the power supply channels on in
any order by activating the PUP outputs and
monitoring the respective converter voltages to ensure
cascading of the supplies. A programmable sequence
termination timer can be set to disable all channels if
the Power-on sequence stalls. During this mode the
HEALTHY output will remain inactive and the RST
output will remain active.
Once the Power-on sequencing mode is complete, the
SMS66 enters monitor mode. In the monitor mode the
SMS66 supervises the supplies to within 5mV, and
enables the triggering of outputs by monitored fault
conditions.
The 10-bit ADC cycles through all 11 channels every
2ms and checks the conversions against the
programmed threshold limits. The results can be used
to trigger RST, HEALTHY and FAULT outputs as well
as to trigger a Power-off or a Force Shutdown
operation.
The Power-off sequencing mode can only be entered
while the SMS66 is in the monitoring mode. It can be
initiated by either bringing the PWR_ON/OFF pin
inactive, through I
2
C control or triggered by a channel
exceeding its programmed thresholds. Once Power-
off is initiated it will disable the Active DC Control and
sequence the PUP outputs off in either the same or
reverse order as Power-on sequencing and monitor
the supply voltages to ensure cascading of the
supplies as they turn off. The sequence termination
timer can be programmed to immediately disable all
channels if the Power-off sequencing stalls. The RST
output will remain active throughout this mode while
the HEALTHY output remains inactive.
Summit Microelectronics, Inc
2070 1.0 7/16/03
2
SUMMIT [ SUMMIT MICROELECTRONICS, INC. ]
