Datasheet

MAX34451 PMBus 16-Channel V/I Monitor and
12-Channel Sequencer/Marginer
www.maximintegrated.com
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VOUT_MODE (20h)
TheVOUT_MODEcommandisusedto reportthedata
formatofthedevice.ThedeviceusestheDIRECTformat
for all the voltage-related commands. The value returned
is40h,indicatingDIRECTdataformat.Thiscommandis
read-only. If a host attempts to write this command, the
CMLstatusbitisasserted.SeeTable5forthem,b,and
Rvaluesforthevariouscommands.
VOUT_MARGIN_HIGH (25h)
The VOUT_MARGIN_HIGH command loads the device
with the voltage to which the power-supply output is to
be changed when the OPERATION command is setto
margin high. If the power supply is already operating at
margin high, changing VOUT_MARGIN_HIGH has no
effect on the output voltage. The device only adjusts
the power supply to the new VOUT_MARGIN_HIGH
voltage after receiving a new margin-high OPERATION
command.The2databytesareinDIRECTformat.Ifthe
device cannot successfully close-loop margin the power
supply, the device keeps attempting to margin the supply
anddoesthefollowing:
1) SetstheMARGINbitinSTATUS_WORD.
2) Sets the MARGIN_FAULT bit in STATUS_MFR_
SPECIFIC(PAGES0–11).
3) NotifiesthehostthroughALERT assertion (if enabled
inMFR_MODE).
VOUT_MARGIN_LOW (26h)
The VOUT_MARGIN_LOW command loads the device
with the voltage to which the power-supply output chang-
estowhentheOPERATIONcommandissettomargin
low. If the power supply is already operating at margin
low, changing VOUT_MARGIN_LOW has no effect on
the output voltage. The device only adjusts the power
supply to the new VOUT_MARGIN_LOW voltage after
receivinganewmargin-lowOPERATIONcommand.The
2databytesareinDIRECTformat.Ifthedevicecannot
successfully close-loop margin the power supply, the
device keeps attempting to margin the supply and does
thefollowing:
1) SetstheMARGINbitinSTATUS_WORD
2) Sets the MARGIN_FAULT bit in STATUS_MFR_
SPECIFIC(PAGES0–11)
3) NotifiesthehostthroughALERT assertion (if enabled
inMFR_MODE).
VOUT_SCALE_MONITOR (2Ah)
In applications where the measured power-supply volt-
ageisnotequaltothevoltageattheADCinput,VOUT_
SCALE_MONITORisused.Forexample,iftheADCinput
expectsa 1.8V input for a 12V output,VOUT_SCALE_
MONITOR=1.8V/12V=0.15.Inapplicationswherethe
power-supply output voltage is greater than the device
input range of 2.048V, the output voltage of the power
supply is sensed through a resistive voltage-divider. The
resistive voltage-divider reduces or scales the output
voltage.ThePMBuscommandsspecifytheactualpower-
supply output voltages and not the input voltage to the
ADC.Toallowthedevicetomapbetweenthehighpower-
supplyvoltages(suchas12V)andthevoltageattheADC
input,theVOUT_SCALE_MONITORcommandisused.
The 2 data bytes are in DIRECT format. This value is
dimensionless. As an example, if the required scaling fac-
toris0.15,thenVOUT_SCALE_MONITORshouldbeset
to1333h(4915/32,767=0.15).SeeTable18.
Table 18. VOUT_SCALE_MONITOR (2Ah) Examples
*The full-scale ADC voltage on the device is 2.048V. A scaling factor where a 1.8V ADC input represents a nominal 100%
voltage level is recommended to allow headroom for margining. Resistor-dividers must be used to measure voltage greater than
1.8V. The maximum source impedance of the resistor-divider is limited by the setting of the ADC_TIME bits in MFR_MODE.
See the
RecommendedOperatingConditions section for details.
NOMINAL VOLTAGE LEVEL
MONITORED
NOMINAL ADC INPUT
VOLTAGE LEVEL*
RESISTIVE DIVIDER
RATIO
VOUT_SCALE_MONITOR
VALUE
1.8Vorless 1.8V 1.0 7FFFh
2.5V 1.8V 0.72 5C28h
3.3V 1.8V 0.545454 45D1h
5V 1.8V 0.36 2E14h
12V 1.8V 0.15 1333h