Technical
Specification
IQ18-HPC Family
Before time t0,ꢀwhenꢀtheꢀinputꢀvoltageꢀisꢀbelowꢀtheꢀUVLꢀthreshold,ꢀ
theꢀunitꢀisꢀdisabledꢀbyꢀtheꢀInputꢀUnder-VoltageꢀLockoutꢀfeature.ꢀ
Whenꢀ theꢀ inputꢀ voltageꢀ risesꢀ aboveꢀ theꢀ UVLꢀthreshold,ꢀ theꢀ
InputꢀUnder-VoltageꢀLockoutꢀisꢀreleased,ꢀandꢀaꢀStartupꢀInhibitꢀ
Periodꢀisꢀinitiated.ꢀꢀAtꢀtheꢀendꢀofꢀthisꢀdelay,ꢀtheꢀON/OFFꢀpinꢀisꢀ
evaluated, and since it is active, the unit turns on.
maximum power the converter can dissipate for a given thermal
conditionꢀifꢀitsꢀbase-plateꢀisꢀtoꢀbeꢀnoꢀhigherꢀthanꢀ100ꢀºC.
100 ºCꢀ-ꢀTA
Pmax
=
dissꢀꢀꢀꢀꢀꢀꢀRTH
BA
Thisꢀvalueꢀofꢀpowerꢀdissipationꢀcanꢀthenꢀbeꢀusedꢀinꢀconjunctionꢀ
withꢀtheꢀdataꢀshownꢀinꢀFigureꢀ2ꢀtoꢀdetermineꢀtheꢀmaximumꢀloadꢀ
currentꢀ(andꢀpower)ꢀthatꢀtheꢀconverterꢀcanꢀdeliverꢀinꢀtheꢀgivenꢀ
thermal condition.
Atꢀtimeꢀt1,ꢀtheꢀunitꢀisꢀdisabledꢀbyꢀtheꢀON/OFFꢀpin,ꢀandꢀitꢀcannotꢀ
beꢀenabledꢀagainꢀuntilꢀtheꢀStartupꢀInhibitꢀPeriodꢀhasꢀelapsed.
Whenꢀ theꢀ ON/OFFꢀ pinꢀ goesꢀ highꢀ afterꢀ t2,ꢀ theꢀ Startupꢀ Inhibitꢀ
Period has elapsed, and the output turns on within the typical
Turn-OnꢀTime.
Forꢀconvenience,ꢀpowerꢀderatingꢀcurvesꢀforꢀanꢀencasedꢀconverterꢀ
without a heatsink and with a typical heatsink are provided for
each output voltage.
ꢁhermal Considerations: The maximum operating base-
plate temperature, TB,ꢀisꢀ100ꢀºC.ꢀAsꢀlongꢀasꢀtheꢀuser’sꢀthermalꢀ
system keeps TB <ꢀ 100ꢀ ºC,ꢀ theꢀ converterꢀ canꢀ deliverꢀ itsꢀ fullꢀ
rated power.
Aꢀpowerꢀderatingꢀcurveꢀcanꢀbeꢀcalculatedꢀforꢀanyꢀheatsinkꢀthatꢀisꢀ
attached to the base-plate of the converter. It is only necessary
toꢀdetermineꢀtheꢀthermalꢀresistance,ꢀRTHBA, of the chosen heatsink
between the base-plate and the ambient air for a given airflow
rate. This information is usually available from the heatsink
vendor. The following formula can the be used to determine the
V
in
Under-Voltageꢀ
LockoutꢀTurn-
OnꢀThreshold
ON/OFF
(negꢀlogic)
ON
OFF
ON
OFF
ON
9ms (typical
turnꢀonꢀtime)
V
out
200ms
(typicalꢀstart-upꢀ
inhibitꢀperiod)
200ms
200ms
t
t0
t1
t2
Figure F: Startup Inhibit Period (turn-on time not to scale)
Product # IQ18xxxHPCxx
Phone 1-888-567-9596
www.synqor.com
Doc.# 005-005029 Rev. B
04/13/09
Page 27
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