Datasheet

MAX34451 PMBus 16-Channel V/I Monitor and
12-Channel Sequencer/Marginer
www.maximintegrated.com
Maxim Integrated │ 64
PWM/DAC Margining Component Selection
The external components needed to realize the margin-
ing circuitry for both the PWM outputs and the current
DACoutputsareshowninFigure14anddescribedinthe
formulasbelow:
PWM“R”=(V
FB
-0.3)/(I
FB
xmarginingrangex120%)
whereV
FB
is the feedback node voltage and I
FB
is the
feedback node current.
Example:
V
FB
=0.8V,I
FB
=10µA,marginingrange=±12%
PWM“R”Value=(0.8–0.3)/(10µAx12%x120%)
=417kΩ
DAC“R
FS
”=(7.75)/(I
FB
xMarginingrangex120%)
where I
FB
is the feedback node current.
Example:
I
FB
=500µA,marginingrange=±15%
DAC“RFS”value=(7.75)/(500µAx15%x120%)=
86kΩ
Note:
40kΩ<R
FS
<160kΩ
Temperature Sensor Operation
The device can monitor up to five different temperature sen-
sors, four external sensors, plus its own internal tempera-
ture sensor. The external temperature sensors are all con-
nected in parallel to the master I
2
Cport(MSDAandMSCL
pins).ThedevicecansupportuptofourDS75LVdevices.
Eachoftheenabledtemperaturesensorsaremeasured
once per second. The internal temperature sensor is
averagedfourtimestoreducetheeffectofnoise.Each
time the device attempts to read a temperature sensor,
itchecksforfaults.Fortheinternaltemperaturesensor,
afaultisdefinedasreadinggreaterthan+130°Corless
than -60°C. For the I
2
C temperature sensors, a fault is
defined as a communication access failure. Temperature-
sensor faults are reported by setting the temperature
reading to 7FFFh.A temperature-sensor fault results in
thesettingoftheTEMPERATUREbitinSTATUS_WORD
and ALERTisasserted(ifenabledinMFR_MODE).No
bitsaresetinSTATUS_TEMPERATURE.Onresetofthe
device,ifthedevicecannotinitializetheexternalDS75LV
device,theTEMPERATUREbitinSTATUS_WORDisset
and ALERTisasserted(ifenabledinMFR_MODE),but
the device does not attempt to reinitialize the DS75LV
until8000hiswrittentoMFR_TEMP_SENSOR_CONFIG.
Reading disabled temperature sensors returns a fixed
valueof0000h.
Up to four DS75LV digital temperature sensors can be
controlled by the MAX34451. The A0–A2 pins on the
DS75LVshouldbeconfiguredasshowninTable41.The
thermostatfunctionontheDS75LVisnotusedandhence
theO.S.outputshouldbeleftopencircuit.
MFR_TEMP_SENSOR_CONFIG (F0h)
TheMFR_TEMP_SENSOR_CONFIGcommandis used
toconfigurethetemperaturesensors.TheMFR_TEMP_
SENSOR_CONFIGcommandisdescribedinTable42.
FS
R
FS
I
FB
V
FB
R
V
OUT
PWMn
POWER SUPPLY
RIPPLE FILTER
MAX34451
FB/ TRIM
4.7kΩ
10nF
I
FB
V
OUT
OUT
POWER SUPPLY
DS4424
FB/ TRIM
Figure 14. Margining Hardware Configurations