Technical
Specification
IQ90-HPC Family
OUꢁPUꢁ VOLꢁAGꢂ ꢁRIM (Pin 6):ꢀTheꢀTRIMꢀinputꢀpermitsꢀtheꢀ
userꢀtoꢀadjustꢀtheꢀoutputꢀvoltageꢀacrossꢀtheꢀsenseꢀleadsꢀupꢀorꢀ
down according to the trim range specifications.
PROTECTIONꢀFEATURES
Input Under-Voltage Lockout:ꢀ Theꢀ converterꢀ isꢀ designedꢀ
to turn off when the input voltage is too low, helping avoid an
input system instability problem, described in more detail in
the application note titled “Inputꢀ Systemꢀ Instability”ꢀ onꢀ ourꢀ
website. The lockout circuitry is a comparator with dc hysteresis.
Whenꢀtheꢀinputꢀvoltageꢀisꢀrising,ꢀitꢀmustꢀexceedꢀtheꢀtypicalꢀTurn-
OnꢀVoltageꢀThresholdꢀvalueꢀ(listedꢀonꢀtheꢀspecificationsꢀpage)ꢀ
beforeꢀ theꢀ converterꢀ willꢀ turnꢀ on.ꢀ Onceꢀ theꢀ converterꢀ isꢀ on,ꢀ
theꢀ inputꢀ voltageꢀ mustꢀ fallꢀ belowꢀ theꢀ typicalꢀ Turn-Offꢀ Voltageꢀ
Threshold value before the converter will turn off.
To decrease the output voltage, the user should connect a
resistorꢀbetweenꢀPinꢀ6ꢀandꢀPinꢀ5ꢀ(SENSE(-)ꢀinput).ꢀForꢀaꢀdesiredꢀ
decrease of the nominal output voltage, the value of the resistor
should be
511
R
=
-ꢀ10.22 (kW)
trim-down
(∆%)
where
Vnominalꢀ–ꢀVdesired
ꢀꢀꢀꢀꢀꢀVnominal
Output Current Limit:ꢀ Theꢀ maximumꢀ currentꢀ limitꢀ remainsꢀ
constant as the output voltage drops. However, once the
impedance of the load across the output is small enough to make
theꢀoutputꢀvoltageꢀdropꢀbelowꢀtheꢀspecifiedꢀOutputꢀDCꢀCurrent-
LimitꢀShutdownꢀVoltage,ꢀtheꢀconverterꢀturnsꢀoff.
=
xꢀ100%
∆%
ꢀ
ꢀ
To increase the output voltage, the user should connect a
resistorꢀbetweenꢀPinꢀ6ꢀandꢀPinꢀ7ꢀ(SENSE(+)ꢀinput).ꢀForꢀaꢀdesiredꢀ
increase of the nominal output voltage, the value of the resistor
should be
Theꢀconverterꢀthenꢀentersꢀaꢀ“hiccupꢀmode”ꢀwhereꢀitꢀrepeatedlyꢀ
turnsꢀonꢀandꢀoffꢀatꢀaꢀ5ꢀHzꢀ(nominal)ꢀfrequencyꢀwithꢀaꢀ5%ꢀdutyꢀ
cycle until the short circuit condition is removed. This prevents
excessive heating of the converter or the load board.
5.11VOUTꢀ (100+∆%)
x
511
_
R
_
=
(kW)
trim-up
10.22
)
(
1.225∆%
∆%
Output Over-Voltage Limit:ꢀIfꢀtheꢀvoltageꢀacrossꢀtheꢀoutputꢀ
pinsꢀexceedsꢀtheꢀOutputꢀOver-VoltageꢀProtectionꢀthreshold,ꢀtheꢀ
converter will immediately stop switching. This prevents damage
toꢀtheꢀloadꢀcircuitꢀdueꢀtoꢀ1)ꢀexcessiveꢀseriesꢀresistanceꢀinꢀoutputꢀ
currentꢀ pathꢀ fromꢀ converterꢀ outputꢀ pinsꢀ toꢀ senseꢀ point,ꢀ 2)ꢀ aꢀ
releaseꢀofꢀaꢀshort-circuitꢀcondition,ꢀorꢀ3)ꢀaꢀreleaseꢀofꢀaꢀcurrentꢀ
limitꢀ condition.ꢀ Loadꢀ capacitanceꢀ determinesꢀ exactlyꢀ howꢀ highꢀ
theꢀoutputꢀvoltageꢀwillꢀriseꢀinꢀresponseꢀtoꢀtheseꢀconditions.ꢀAfterꢀ
200ꢀmsꢀtheꢀconverterꢀwillꢀautomaticallyꢀrestart.
where
V
ꢀ=ꢀNominalꢀOutputꢀVoltage
out
Trim graphs show the relationship between the trim resistor
valueꢀandꢀRtrim-upꢀandꢀRtrim-down,ꢀshowingꢀtheꢀtotalꢀrangeꢀtheꢀ
output voltage can be trimmed up or down.
Note:ꢀtheꢀTRIMꢀfeatureꢀdoesꢀnotꢀaffectꢀtheꢀvoltageꢀatꢀwhichꢀtheꢀ
output over-voltage protection circuit is triggered. Trimming the
output voltage too high may cause the over-voltage protection
circuit to engage, particularly during transients.
Over-ꢁemperature Shutdown:ꢀ Aꢀ temperatureꢀ sensorꢀ onꢀ
the converter senses the average temperature of the module.
The thermal shutdown circuit is designed to turn the converter
off when the temperature at the sensed location reaches the
Over-Temperatureꢀ Shutdownꢀ value.ꢀ Itꢀ willꢀ allowꢀ theꢀ converterꢀ
to turn on again when the temperature of the sensed location
fallsꢀbyꢀtheꢀamountꢀofꢀtheꢀOver-TemperatureꢀShutdownꢀRestartꢀ
Hysteresis value.
It is not necessary for the user to add capacitance at the Trim
pin. The node is internally bypassed to eliminate noise.
ꢁotal DC Variation of V
specifications,ꢀtheꢀmaximumꢀvariationꢀofꢀtheꢀdcꢀvalueꢀofꢀV
:ꢀForꢀtheꢀconverterꢀtoꢀmeetꢀitsꢀfullꢀ
OUꢁ
, due
OUT
to both trimming and remote load voltage drops, should not be
greater than that specified for the output voltage trim range.
Product # IQ90xxxHPCxx
Phone 1-888-567-9596
www.synqor.com
Doc.# 005-0005060 Rev. B
01/29/09
Page 25
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