SMH4046
Preliminary Information
Summit Microelectronics, Inc
2082 1.7 08/23/04
3
The device also triggers outputs by monitoring fault
conditions.
The 10-bit ADC cycles through all
channels every 2 ms and checks the conversions
against the programmed threshold limits. The results
can be used to trigger the RESET, HEALTHY# and
FAULT outputs as well as to trigger a power-off or a
force- shutdown operation.
While the SMH4046 is in monitoring mode, a serial
interface command to margin the supply voltages can
bring the part into margining mode. In margining mode
the SMH4046 can margin the three supply voltages in
any combination of nominal, high or low voltage
settings using the ADOC feature, all to within ±0.5%.
The margin high and margin low voltage settings can
range from 0.9V to the overvoltage limit of the DC-DC
converters and depends on the margin range of the
converters. During this mode the HEALTHY# output is
always active and the RESET output is always inactive
regardless of the voltage threshold limit settings and
triggers. Furthermore, the triggers for power-off and
force-shutdown are temporarily disabled.
The power-off sequencing mode can only be entered
while the SMH4046 is in the monitoring mode. It can
be initiated by either bringing the HST_PWR pin
inactive, through the serial interface control, or
triggered by a channel exceeding its programmed
thresholds. Once power-off is initiated, active DC
control is disabled, and the PUP outputs are
sequenced off in either the same or reverse order as
power-on sequencing. Monitoring of the supply
voltages continues 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 RESET output
remains active throughout this mode while the
HEALTHY# output remains inactive.
The CARD_3V and CARD_5V monitor pins are also
used to detect overcurrents on the card side 3V and
5V supply. The FAULT pin is a programmable active
high/low open drain fault output that is asserted by the
SMH4046 when a programmed fault condition occurs
on the internal/external temperature sensor. If
programmed to do so, FAULT is asserted whenever
an over-current condition is detected. Fault will be
released at the same time that the VGATE outputs are
turned back on after a reset from the host on the
HST_PWR pin. Programming is accomplished by
using the I
2C serial bus interface.
GENERAL DESCRIPTION (CONTINUED)
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