Datasheet

MAX34451 PMBus 16-Channel V/I Monitor and
12-Channel Sequencer/Marginer
www.maximintegrated.com
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Conversely,ifthehost received a value of 0D89h on a
READ_VOUTcommand,thisisequivalentto:
X=(1/1)x(0D89hx10
-(-0)
–0)=3465mV=3.465V
Power supplies and power converters generally have
no way of knowing how their outputs are connected to
ground.Withinthepowersupply,alloutputvoltagesare
most commonly treated as positive. Accordingly, all out-
put voltages and output-voltage-related parameters of
PMBusdevicesarecommandedandreportedaspositive
values. It is up to the system to know that a particular
output is negative if that is of interest to the system. All
output-voltage-related commands use 2 data bytes.
Fault Management and Reporting
For reporting faults/warnings to the host on a real-time
basis, the device asserts the open-drain ALERT pin (if
enabledinMFR_MODE)andsetstheappropriatebitin
the various status registers. On recognition of the ALERT
assertion, the host or system manager is expected to poll
the I
2
C bus to determine the device asserting ALERT.
ThehostsendstheSMBusARA(0001100).Thedevice
ACKstheSMBusARA,transmitsitsslaveaddress,and
deasserts ALERT. The system controller then communi-
cateswithPMBuscommandstoretrievethefault/warning
status information from the device.
See the individual command sections for more details.
Faultsandwarningsthatarelatchedinthestatusregis-
ters are cleared when any one of the following conditions
occur:
● ACLEAR_FAULTScommandisreceived.
● TheRST pin is toggled or a soft-reset is issued.
● Bias power to the device is removed and then
reapplied.
One or more latched-off power supplies are only restarted
whenoneofthefollowingoccurs:
● OPERATIONcommandsarereceivedthatturnoffand
turnonthepowersupplies,ortheCONTROLnpinsare
toggled to turn off and then turn on the power supplies.
● TheRST pin is toggled or a soft-reset is issued.
● Bias power to the device is removed and then
reapplied.
The device responds to fault conditions according to
the configuration of the MFR_FAULT_RESPONSE
command. This command determines how the device
should respond to each particular fault and whether it
should assert one or more of the FAULTn pins when a
fault occurs.
The MFR_FAULT_RESPONSE command also deter-
mines whether a channel should power up if a fault is
present. With the RESPONSE bits in MFR_FAULT_
RESPONSE, each channel can be independently con-
figured to either respond or not respond to each possible
fault. Before any power-supply channel is enabled, or
the FAULTn outputs deasserted, the device checks for
overvoltage, overcurrent, and temperature faults (but not
forundervoltage)ifthechannelisconfiguredforafault
responsetoeitherlatchoff(RESPONSE[1:0]=01)orretry
(RESPONSE[1:0]=10)intheMFR_FAULT_RESPONSE
command. Only after the faults clear is the channel
allowedtoturnon.SeeTable7forfault-monitoringstates.
Table 7. Fault-Monitoring States
Note: Device response to faults is determined by the configuration of MFR_FAULT_RESPONSE.
FAULT
REQUIRED DEVICE CONFIGURATION
FOR ACTIVE MONITORING
WHEN MONITORED
Overvoltage
•
Voltagemonitoringenabled
(SELECT[5:0]=10hor20hinMFR_CHANNEL_CONFIG)
Continuous monitoring.
Undervoltage
•
Voltagemonitoringenabled
(SELECT[5:0]=10hor20hinMFR_CHANNEL_CONFIG)
Stopmonitoringwhilethepowersupplyis
off;startmonitoringwhenvoltageexceeds
thePOWER_GOOD_ONlevel.
Overcurrent
•
Currentmonitoringenabled
(SELECT[5:0]=22hinMFR_CHANNEL_CONFIG)
Continuous monitoring.
Power-UpTime
• Sequencingenabled
(SELECT[5:0]=10hinMFR_CHANNEL_CONFIG)
Monitored only during power-on sequence.
Overtemperature
• Temperature sensor enabled
(ENABLE=1inMFR_TEMP_SENSOR_CONFIG)
Continuous monitoring.