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Rev. 1.10 1 April 18, 2014 Rev. 1.00 PB April 18, 2014
HT7465Step-Down DC to DC Converter
Feature• Inputvoltagerange:4.75Vto24V• Variableoutputvoltagerange:0.92Vto20V• 2Aoutputcurrent• Efficiencyupto92%• Fixed380kHzoperatingfrequency• 20mAshutdowncurrent• InternalpowerMOSFETswitch• StableoperationusinglowESRceramiccapacitors• Overtemperatureprotection• Cycle-by-cycleovercurrentprotection• Undervoltagelockoutprotection• 8-pinSOPpackage
Applications• Batterychargers• Distributedpowersystems• LEDdriver• DSLmodems• Linearregulatorprepowerprocessing• Set-Top-Boxes,DVDplayers,LCDdisplays
General DescriptionTheHT7465isa2Ahighefficiencystep-downDC-DCconverterwhichincludesafullyintegratedMOSpower transistor.Thedeviceuses a current-modecontroloperatingmethodologyandcanoperateoverawideinputvoltagerangeof4.75Vto24Vforwhichitcanprovideastableadjustableoutputvoltage.
Thedevice includesover temperatureprotection,overcurrentprotectionandundervoltage lockoutprotection,featureswhichcombinetopreventdevicedamageduetooverloadconditions.In itsshutdownmode the regulatordrawsamere20uAof supplycurrent.
Thedevice isavailable in8-pinSOPpackage typeandprovidesaverycompactsystemsolutionwithaminimumofexternalcomponents.
Application Circuits
B230A
VIN
EN
GND COMP
HT7465
BS
SW
FB
22uF
10 F
L
10nF
R2
R1
VIN
VOUT
2
21
RRRVV FBOUT
4.75~24V
C4
C1C2
R3
C6C5
10/15 H
Efficiency vs Output Current
Rev. 1.10 2 April 18, 2014
HT7465
Block Diagram
RegulatorUnder-voltage
lockout
EN NC
Amplifier CurrentSense
ControlLogic
Current Sense
Soft-Start
PWM Comparator
OSC240/380kHz
ErrorAmplifier
0.92V
SCP
COMPFB
VIN
BS
SW
5V
GND
+ -
+
-
+
-
Pin Assignment
1234
8765
BSVINSW
GND
NCENCOMPFB
HT74658 SOP-A
(Exposed Pad)
PAD(GND)
Rev. 1.10 3 April 18, 2014
HT7465
Absolute Maximum RatingsMaximumInputSupplyVoltage............................26VSwitchNodeVoltage..............................................26VFeedbackVoltage.....................................................6V
ENVoltage...............................................................6VCompVoltage...........................................................6VMaximumJunctionTemperature....................... 150°C
Pin DescriptionPin No. Pin Name Description
1 BSInternal Power NMOS Gate Drive Boost Input.A 10nF or greater value capacitor should be connected from SW to BS for additional Power NMOS gate driving purposes.
2 VINPower supply input.The input supply pin for the device, VIN, is connected to a supply voltage between 4.75V to 24V.
3 SW Power switching output.The internal power MOS drain is connected to the inductor diode and VIN.
4 GND Ground.Device ground voltage reference.
5 FBFeedback pin.The feedback pin is connected to an external resistor divider to measure the output voltage.
6 COMP
Error Amplifier Output.Used for compensation of the regulation control loop. Connect a series RC network from COMP to GND to compensate the regulation control loop and the COMP pin value is 0.92V.
7 ENEnable Input and dimming control.This pin is set high to turn on the regulator and low to turn it off. The pin should be left unconnected if not used.
8 NC Not used
Exposed Pad GND Ground.Device ground voltage reference.
Note:Thesearestressratingsonly.Stressesexceedingtherangespecifiedunder“AbsoluteMaximumRatings”maycausesubstantialdamagetothedevice.Functionaloperationofthisdeviceatotherconditionsbeyondthoselistedin thespecificationisnot impliedandprolongedexposuretoextremeconditionsmayaffectdevicereliability.
Recommended Operating ConditionsInputSupplyVoltage................................4.75V~24V AmbientTemperatureRange............... -40°C~+85°C
Rev. 1.10 4 April 18, 2014
HT7465
Electrical CharacteristicsVIN=12V,Ta=25°C,unlessotherwisespecifiedrefertocircuitofFigure1.( note 1)
Symbol Parameter Test Condition Min. Typ. Max. Unit
VFB Feedback Voltage 4.75V ≤ VIN ≤ 24V 0.892 0.920 0.948 V
VUVLO Under Voltage Lockout Threshold — — 4.1 — V
— Under Voltage Lockout Threshold Hysteresis — — 200 — mV
IQ Quiescent Current VFB=1.2V, VEN=High — 1.1 1.3 mA
ISS Shutdown Supply Current VEN=0V — 20 30 mA
FOS Oscillator Frequency — — 380 — kHz
— Short Circuit Frequency VFB=0V — 240 — kHz
DMAX Maximum Duty Cycle VFB=0.6V — 90 — %
ISW Switch Leakage VEN=0V, VSW=0V — 0 10 mA
RDS Switch On Resistance (note 2) IOUT=2A — 0.18 — W
ILIMIT Current Limit — — 3.4 — A
— Error Amplifier Voltage Gain (note 2) — — 70 — dB
— Error Amplifier Trans-conductance (note 2) — — 800 — mA/V
VEN Enable Threshold 4.75V ≤ VIN ≤ 24V 0.7 1.0 1.3 V
TJ Thermal Shutdown — — 150 — °C
Note:1.Specificationsareproduction testedatTa=roomtemperature.Specificationsover the-40°C to85°Coperating temperaturerangeareassuredbydesign,characterizationandcorrelationwithStatisticalQualityControls(SQC).
2.Thetestspecificationsbydesigner.
Rev. 1.10 5 April 18, 2014
HT7465
Functional Description
Setting the Output VoltageTheHT7465 is a step down switchingDC/DCconverterdevice.Thedeviceswitchingoutput,SW,isconnectedtoastandardconverterLCfiltercircuitforbuckconversion.Theoutputcurrent issensedusinganexternalvoltagedividernetworkconnectedtotheloadoutputvoltageandground,andthesensevoltagefeedbacktothedeviceontheFBpin.Bycomparingthis sense voltagewith an internally generated0.92voltage reference, suitable regulationcanbeimplementedtoachievetherequiredoutputvoltage.By selecting suitable values of external voltagedivider resistors, thedesiredoutputvoltagecanbeadjustedtotherequiredlevel.Theoutputvoltagecanbecalculatedusingthefollowingformula:
VOUT=x0.92R1+R2R2
whereR2istheresistordividerlowerresistorandR1istheupperresistor.
Compensation ComponentsCare must be taken when selecting externalcomponents.TheCOMPpin is the output of theerroramplifierandmustbeproperlyconnectedtoanexternalRCnetworktoensureregulatorloopstability.Thevaluesof thecompensationcomponentsgiveninTable1yieldastablecontrol loopfor theoutputvoltageandcapacitorgiven.
Table1CompensationValues forTypicalOutputVoltage/CapacitorCombinations.
VOUT L R3 C4 C6 C5
2.5 10/15mH 9.1K 2.2n 22mF Ceramic —
3.3 10/15mH 10K 3.9n 22mF Ceramic —
5.0 10/15mH 18K 1.5n 22mF Ceramic —
Current Limit ProtectionThedevicehas a cycle-by-cycle current limit toprotect the internalpowerMOSFET.If the inductorcurrent reaches thecurrent limit thresholdof3.4A,theMOSFEToscillatorfrequencywillbetransformedfrom380kHztoashortcircuitfrequencyof240kHzandtheoutputcurrentwillremainatitscurrentlimitvalue.
Over — Temperature ProtectionA thermal shutdown function is implemented topreventdamagesdue toexcessiveheatandpowerdissipation.Typicallythethermalshutdownthresholdtemperatureis150°C.Whenthethermalshutdownis
triggeredthedevicestopsswitchingandwillrequireapoweron inputvoltage signal,before resumingswitchingoperation.
Application Information
InductorTheinductorisrequiredtosupplyaconstantcurrenttotheoutputloadwhilebeingdrivenbytheswitchedinputvoltage.Thechoiceof inductoraffectssteadystate operation aswell as transient behavior andloopstability.Thereare three importantelectricalparameterswhich need to be consideredwhenchoosinganinductor:
• Theinductorvalue• DCR-copperwireresistance• ThesaturationcurrentInductor choice is especially important as it isimportant toensure the inductordoesnot saturateunderitspeakcurrentconditions.AlsoensurethattheinductorhasalowDCRtominimisepowerlosses.
Input/Output CapacitorInput CapacitorBecausetheVINpinisconnectedtotheinternalpowerMOSFET,whenthepowerMOSFETisswitchingandtheinputcurrentisdiscontinuous,thereforeaninputcapacitorC1 is required to supply theACcurrentto the step-downconverterwhilemaintaining theDCinputvoltage.A lowESRceramiccapacitor isrequiredtokeepnoisetoaminimum.
Output CapacitorTheoutputcapacitor isrequiredtomaintaintheDCoutput voltage.Ceramicor lowESRelectrolyticcapacitors is the rule to choice of external loadcapacitorisalsocriticalandlowESRvaluecapacitorsmustbeusedtoensurestability.Thiscapacitormustbeconnectedveryclose to the inductor,withshorttracesforgoodnoiseperformance.
Schottky DiodeTheoutputdiodeconductswhenthe internalpowerMOSFETisswitchedoff.Therearethreeimportantelectricalparameters toconsiderwhenchoosingthediode:
• Thediodemaximumreversevoltagevaluemustgreaterthanthemaximuminputvoltage
• Shortrecoverytime--useSchottkydiode• Diodecurrentratingshouldbegreaterthanthemaximumloadcurrent
Rev. 1.10 6 April 18, 2014
HT7465
Layout ConsiderationsCircuitboardlayoutisaveryimportantconsiderationfor switching regulators if they are to functionproperly.Poorcircuit layoutmay result in relatednoise problems. In order tominimise EMI andswitchingnoise,followtheguidelinesbelow:
• Alltracksshouldbeaswideaspossible.• Theinputandoutputcapacitors,C1(C8)andC6(C7),shouldbeplacedclosetotheVIN,VOUTandGNDpins(C1andC8isparallel;C6andC7isparallel).
• TheSchottkydiodeDandinductorLmustbeplacedclosectotheSWpin.
• Feedbackresistor,R1(R1-1)andR2,mustbeplacedclosetotheFBandGNDpins(R1andR1-1isseries).
• AfullgroundplaneisalwayshelpfulforbetterEMIperformance.
A recommended PCB layout with componentlocationsisshownbelow.
Top Layer
Bottom Layer
Rev. 1.10 7 April 18, 2014
HT7465
Package Information
Notethat thepackageinformationprovidedhereisforconsultationpurposesonly.Asthis informationmaybeupdatedatregularintervalsusersareremindedtoconsulttheHoltekwebsiteforthelatestversionofthePackage/CartonInformation.
Additionalsupplementaryinformationwithregardtopackagingislistedbelow.Clickontherelevantsectiontobetransferredtotherelevantwebsitepage.
• FurtherPackageInformation(includeOutlineDimensions,ProductTapeandReelSpecifications)
• PackingMeterialsInformation
• Cartoninformation
Rev. 1.10 8 April 18, 2014
HT7465
8-pin SOP_EP (150mil) Outline Dimensions for Thermally Enhanced Variations Only (Exposed Pad)
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SymbolDimensions in inch
Min. Nom. Max.A ― 0.236 BSC ―B ― 0.154 BSC ―C 0.012 ― 0.020C' ― 0.193 BSC ―D ― ― 0.069
D1 0.059 ― ―E ― 0.050 BSC ―
E2 0.039 ― ―F 0.004 ― 0.010G 0.016 ― 0.050H 0.004 ― 0.010α 0° ― 8°
SymbolDimensions in mm
Min. Nom. Max.A ― 6.00 BSC ―B ― 3.90 BSC ―C 0.31 ― 0.51C' ― 4.90 BSC ―D ― ― 1.75
D1 1.50 ― ―E ― 1.27 BSC ―
E2 1.00 ― ―F 0.10 ― 0.25G 0.40 ― 1.27H 0.10 ― 0.25α 0° ― 8°
Rev. 1.10 9 April 18, 2014
HT7465
Copyright© 2014 by HOLTEK SEMICONDUCTOR INC.
The information appearing in this Data Sheet is believed to be accurate at the time of publication. However, Holtek assumes no responsibility arising from the use of the specifications described. The applications mentioned herein are used solely for the purpose of illustration and Holtek makes no warranty or representation that such applications will be suitable without further modification, nor recommends the use of its products for application that may present a risk to human life due to malfunction or otherwise. Holtek's products are not authorized for use as critical components in life support devices or systems. Holtek reserves the right to alter its products without prior notification. For the most up-to-date information, please visit our web site at http://www.holtek.com.
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