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IQ32018HPC55NRS Datasheet(PDF) 8 Page - SynQor Worldwide Headquarters |
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IQ32018HPC55NRS Datasheet(HTML) 8 Page - SynQor Worldwide Headquarters |
8 / 12 page Technical Specification IQ32-HPC Family Product # IQ32xxxHPCxx Phone 1-888-567-9596 www.synqor.com Doc.# 005-005H332 Rev. 1 08/13/08 Page 8 PRELIMINARY Figure A: Various circuits for driving the ON/OFF pin. Figure B: Internal ON/OFF pin circuitry BASICOPERATIONANDFEATURES This converter series uses a two-stage power conversion topology. The first stage is a buck-converter that keeps the output voltage constant over variations in line, load, and temperature. The second stage uses a transformer to provide the functions of input/output isolation and voltage step-up or step-down to achieve the output voltage required. Both the first stage and the second stage switch at a fixed frequency for predictable EMI performance. Rectification of the transformer’s output is accomplished with synchronous rectifiers. These devices, which are MOSFETs with a very low on-state resistance, dissipate far less energy than Schottky diodes. This is the primary reason that the converter has such high efficiency, even at very low output voltages and very high output currents. These converters are offered totally encased to withstand harsh environmentsandthermallydemandingapplications.Dissipation throughout the converter is so low that it does not require a heatsink for operation in many applications; however, adding a heatsink provides improved thermal derating performance in extreme situations. This series of converters use the industry standard footprint and pin-out configuration. CONTROLFEATURES ReMOTe On/OFF (Pin 2):TheON/OFFinput,Pin2,permits the user to control when the converter is on or off. This input is referenced to the return terminal of the input bus, Vin(-). TheON/OFFsignalisactivelow(meaningthatalowturnsthe converteron).FigureAdetailsfourpossiblecircuitsfordriving theON/OFFpin.FigureBisadetailedlookoftheinternalON/ OFFcircuitry. ReMOTe SenSe(+) (Pins 7 and 5): The SENSE(+) inputs correct for voltage drops along the conductors that connect the converter’soutputpinstotheload. Pin 7 should be connected to Vout(+) and Pin 5 should be connectedtoVout(-)atthepointontheboardwhereregulation is desired. A remote connection at the load can adjust for a voltage drop only as large as that specified in this datasheet, that is [Vout(+)-Vout(-)]–[Vsense(+)-Vsense(-)] < SenseRange%xVout Pins 7 and 5 must be connected for proper regulation of the output voltage. If these connections are not made, the converter will deliver an output voltage that is slightly higher than its specified value. Note: the output over-voltage protection circuit senses the voltage across the output (pins 8 and 4) to determine when it should trigger, not the voltage across the converter’s sense leads(pins7and5).Therefore,theresistivedropontheboard should be small enough so that output OVP does not trigger, even during load transients. OpenCollectorEnableCircuit RemoteEnableCircuit DirectLogicDrive NegativeLogic (PermanentlyEnabled) ON/OFF Vin(_ ) ON/OFF ON/OFF Vin(_ ) ON/OFF 5V TTL/ CMOS Vin(_ ) Vin(_ ) TTL 5V 50k 50k ON/OFF Vin(_) 100pF OUTPUT VOLTAGe TRIM (Pin 6):TheTRIMinputpermitsthe usertoadjusttheoutputvoltageacrossthesenseleadsupor down according to the trim range specifications. To decrease the output voltage, the user should connect a resistorbetweenPin6andPin5(SENSE(-)input).Foradesired decrease of the nominal output voltage, the value of the resistor should be Rtrim-down = (511)-10.22 (kW) ∆% where ∆% = Vnominal–Vdesired x100% Vnominal To increase the output voltage, the user should connect a resistorbetweenPin6andPin7(SENSE(+)input).Foradesired increase of the nominal output voltage, the value of the resistor should be Graphs on Page 3 show the relationship between the trim resistorvalueandRtrim-upandRtrim-down,showingthetotal range the output voltage can be trimmed up or down. Note:theTRIMfeaturedoesnotaffectthevoltageatwhichthe 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. It is not necessary for the user to add capacitance at the Trim pin. The node is internally bypassed to eliminate noise. Total DC Variation of VOUT:Fortheconvertertomeetitsfull specifications, the maximum variation of the dc value of VOUT, due to both trimming and remote load voltage drops, should not be greater than that specified for the output voltage trim range. PROTECTIONFEATURES Input Under-Voltage Lockout: The converter is designed 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 “Input System Instability” on our website. The lockout circuitry is a comparator with dc hysteresis. Whentheinputvoltageisrising,itmustexceedthetypicalTurn- On Voltage Threshold value (listed on the specifications page) before the converter will turn on. Once the converter is on, the input voltage must fall below the typical Turn-Off Voltage Threshold value before the converter will turn off. Output Current Limit: The maximum current limit remains constant as the output voltage drops. However, once the impedance of the load across the output is small enough to make theoutputvoltagedropbelowthespecifiedOutputDCCurrent- LimitShutdownVoltage,theconverterturnsoff. Theconverterthenentersa“hiccupmode”whereitrepeatedly turnsonandoffata5Hz(nominal)frequencywitha5%duty cycle until the short circuit condition is removed. This prevents excessive heating of the converter or the load board. Output Over-Voltage Limit:Ifthevoltageacrosstheoutput pinsexceedstheOutputOver-VoltageProtectionthreshold,the converter will immediately stop switching. This prevents damage totheloadcircuitdueto1)excessiveseriesresistanceinoutput current path from converter output pins to sense point, 2) a releaseofashort-circuitcondition,or3)areleaseofacurrent limit condition. Load capacitance determines exactly how high theoutputvoltagewillriseinresponsetotheseconditions.After 200mstheconverterwillautomaticallyrestart. Over-Temperature Shutdown: A temperature sensor on 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-Temperature Shutdown value. It will allow the converter to turn on again when the temperature of the sensed location fallsbytheamountoftheOver-TemperatureShutdownRestart Hysteresis value. Rtrim-up (kW) where Vout=NominalOutputVoltage 511 _ 10.22 5.11VOUTx (100+∆%) 1.225 ∆% ∆% ) = ( _ APPLICATIONCONSIDERATIONS Input System Instability: This condition can occur because any dc-dc converter appears incrementally as a negative resistance load. A detailed application note titled “Input SystemInstability”isavailableontheSynQorwebsite which provides an understanding of why this instability arises, and shows the preferred solution for correcting it. Application Circuits: Figure D provides a typicalcircuit diagram which details the input filtering and voltage trimming. Input Filtering and external Capacitance: FigureE provides a diagram showing the internal input filter components. This filter dramatically reduces input terminal ripple current, which otherwise could exceed the rating of an external electrolytic input capacitor. The recommended external input capacitance is specified in the Input Characteristics section on the Electrical Characteristics page.More detailed information is available in the application note titled “EMICharacteristics”ontheSynQorwebsite. Startup Inhibit Period:TheStartupInhibitPeriodensuresthat theconverterwillremainoffforapproximately200mswhenitis shutdownforanyreason.Whenanoutputshortispresent,this generates a 5 Hz “hiccup mode,” which prevents the converter from overheating. In all, there are seven ways that the converter canbeshutdown,initiatingaStartupInhibitPeriod: • InputUnder-VoltageLockout • InputOver-VoltageShutdown • OutputOver-VoltageProtection • OverTemperatureShutdown • CurrentLimit • ShortCircuitProtection • TurnedoffbytheON/OFFinput FigureFshowsthreeturn-onscenarios,whereaStartupInhibit Period is initiated at t0, t1, and t2: Vin External Input Filter Trim Vin(+) Iload Cload L Vout(+) Rtrim-up or Rtrim-down Vsense(+) ON/OFF Vin(_) Vin(+) Vin(_) Vout(_) Vsense(_) Electrolytic Capacitor Figure D: Typical application circuit (negative logic unit, permanently enabled). Figure E: Internal Input Filter Diagram (component values listed on the specifications page). C Beforetimet0,whentheinputvoltageisbelowtheUVLthreshold, theunitisdisabledbytheInputUnder-VoltageLockoutfeature. When the input voltage rises above the UVLthreshold, the InputUnder-VoltageLockoutisreleased,andaStartupInhibit Periodisinitiated.Attheendofthisdelay,theON/OFFpinis evaluated, and since it is active, the unit turns on. Attimet1,theunitisdisabledbytheON/OFFpin,anditcannot beenabledagainuntiltheStartupInhibitPeriodhaselapsed. When the ON/OFF pin goes high after t2, the Startup Inhibit Period has elapsed, and the output turns on within the typical Turn-OnTime. Thermal Considerations: The maximum operating base- plate temperature, TB,is100ºC.Aslongastheuser’sthermal system keeps TB < 100 ºC, the converter can deliver its full rated power. Apowerderatingcurvecanbecalculatedforanyheatsinkthatis attached to the base-plate of the converter. It is only necessary todeterminethethermalresistance,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 maximum power the converter can dissipate for a given thermal conditionifitsbase-plateistobenohigherthan100ºC. P max = 100 ºC-TA diss RTHBA Thisvalueofpowerdissipationcanthenbeusedinconjunction withthedatashowninFigure2todeterminethemaximumload current(andpower)thattheconvertercandeliverinthegiven thermal condition. Forconvenience,Figures3and4providePowerderatingcurves for an encased converter without a heatsink and with a typical 1/4"highheatsink. Figure F: Startup Inhibit Period (turn-on time not to scale) Under-Voltage LockoutTurn- OnThreshold ON/OFF (neglogic) Vout Vin 200ms 200ms 200ms (typical start-up inhibitperiod) t0 t1 t2 t 9ms (typical turnontime) ON ON ON OFF OFF |
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