UC1572 UC2572 UC3572 Negative Output Flyback Pulse Width Modulator FEATURES DESCRIPTION • Simple Single InductorFlybackPWM The UC3572 is a negative output flyback pulse width modulator which con- for Negative Voltage Generation verts a positive input voltage to a regulated negative output voltage. The chipisoptimizedforuseinasingleinductornegativeflybackswitchingcon- • Drives ExternalPMOSSwitch verter employing an external PMOS switch. The block diagram consists of • ContainsUVLOCircuit aprecisionreference,anerroramplifierconfiguredforvoltagemodeopera- tion, an oscillator, a PWM comparator with latching logic, and a 0.5A peak • Includes Pulse-by-Pulse Current Limit gate driver.The UC3572 includes an undervoltage lockout circuit to insure • Low 50µA Sleep Mode Current sufficient input supply voltage is present before any switching activity can occur,andapulse-by-pulsecurrentlimit.Outputcurrentcanbesensedand limited to a user determined maximum value. The UVLO circuit turns the chip off when the input voltage is below the UVLO threshold.In addition, a sleepcomparatorinterfacestotheUVLOcircuittoturnthechipoff.Thisre- ducesthesupplycurrenttoonly50µA,makingtheUC3572idealforbattery powered applications. BLOCK DIAGRAM UDG-94094-2 SLUS275A - MARCH 1999 - REVISED AUGUST 2001

UC1572 UC2572 UC3572 ABSOLUTE MAXIMUM RATINGS CONNECTION DIAGRAM VCC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35V DIL-8,SOIC-8(TOP VIEW) EAINV. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-0.6V toVCC D,N or J Packages IEAOUT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25mA RAMP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-0.3V to 4V CS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-0.3V toVCC Iout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-0.7A to 0.7A I3VREF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-15mA Storage Temperature . . . . . . . . . . . . . . . . . . .-65°C to +150°C Junction Temperature. . . . . . . . . . . . . . . . . . .-65°C to +150°C Lead Temperature (Soldering, 10 sec.). . . . . . . . . . . . .+300°C Currents are positive into, negative out of the specified terminal.ConsultPackagingSectionofDatabookforthermal limitations and considerations of packages. ORDERING INFORMATION TEMPERATURE RANGE PACKAGE UC1572 –55°C to +125°C J UC2572 –40°C to +85°C D, N or J UC3572 0°C to +70°C D or N ELECTRICAL CHARACTERISTICS:Unless otherwise specified,VCC= 5V, CT = 680pF, TA=TJ. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS Reference Section 3VREF 2.94 3 3.06 V Line Regulation VCC= 4.75 to 30V 1 10 mV Load Regulation I3VREF= 0V to –5mA 1 10 mV Oscillator Section Frequency VCC= 5V to 30V 85 100 115 kHz Error Amp Section EAINV EAOUT= 2V –10 0 10 mV IEANV= –1mA –0.2 –0.9 V IEAINV EAOUT= 2V –0.2 –1.0 A AVOL EAOUT= 0.5V to 3V 65 90 dB EAOUTHigh EAINV= –100mV 3.6 4 4.4 V EAOUTLow EAINV= 100mV 0.1 0.2 V IEAOUT EAINV= –100mV,EAOUT= 2V –350 –500 µA EAINV= 100mV,EAOUT= 2V 7 20 mA Unity Gain Bandwidth TJ= 25°C, F = 10kHz 0.6 1 MHz Current SenseComparatorSection Threshold 0.185 0.205 0.225 V Input Bias Current CS = 0 –0.4 –1 µA CSPropogationDelay 300 nS 2

UC1572 UC2572 UC3572 ELECTRICAL CHARACTERISTICS:Unless otherwise specified,VCC= 5V, CT = 680pF, TA=TJ. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS Gate Drive Output Section OUT High Saturation IOUT= 0 0 0.3 V IOUT= –10mA 0.7 1.5 V IOUT= –100mA 1.5 2.5 V OUT Low Saturation IOUT= 10mA 0.1 0.4 V IOUT= 100mA 1.5 2.2 V Rise Time TJ= 25°C,CLOAD= 1nF + 3.3 Ohms 30 80 nS Fall Time TJ= 25°C,CLOAD= 1nF + 3.3 Ohms 30 80 nS Pulse Width Modulator Section Maximum Duty Cycle EAINV= +100mV,VCC= 5V to 30V 92 96 % Minimum Duty Cycle EAINV= –100mV,VCC= 5V to 30V 0 % Modulator Gain EAOUT= 1.5V to 2.5V 45 55 65 %/V UndervoltageLockout Section Start Threshold 3.5 4.2 4.5 V Hysteresis 100 200 300 mV Sleep Mode Section Threshold 1.8 2.2 2.6 V Supply Current Section IVCC VCC= 5V, 30V 9 15 mA VCC= 30, CS = 3V 50 150 A UDG-94095 Figure 1.Typical waveforms. 3

UC1572 UC2572 UC3572 PIN DESCRIPTIONS 3VREF: Precision 3V reference. Bypass with 100nF ca- OUT: Gate drive for external PMOS switch connected pacitor toGND. between VCC and the flyback inductor. OUT drives the gate of thePMOSswitch betweenVCCandGND. CS: Current limit sense pin. Connect to a ground refer- enced current sense resistor in series with the flyback in- RAMP: Oscillator and ramp for pulse width modulator. ductor. OUT will be held high (PMOS switch off) if CS Frequency is set by a capacitor toGNDby the equation exceeds 0.2V. 1 F= EAINV: Inverting input to error amplifier. Summing junc- 15k•CRAMP tion for 3VREF and VOUT sense.The non-inverting input Recommended operating frequency range is 10kHz to of the error amplifier is internally connected to GND.This 200kHz. pin will source a maximum of 1mA. VCC:Input voltage supply to chip.Range is 4.75 to 30V. EAOUT:Outputoferroramplifier.UseEAOUTandEAINV Bypass with a 1µF capacitor. for loop compensation components. GND:Circuit Ground. VIN RSLEEP3 SLEEP 1MEG M SLEEP CV CC C 10µF UC1572 10IµNF 4 VCC C3V OUT 5 REF 100nF MSWITCH 8 3VREF C RAMP 680pF R RREF 7 RAMP S5L6EkEP1 1 EAINV L FLYBACK R COMP 2 EAOUT RSLEEP2 DFLYBACK C 33k COMP CS 3 6 GND R GND CS GND –12VOUT RV COUT 40kSENSE 100µF VOUT UDG-99057 Figure 2.Typical application:+5V to –12Vflybackconverter. 4

PACKAGE OPTION ADDENDUM www.ti.com 18-Sep-2008 PACKAGING INFORMATION OrderableDevice Status(1) Package Package Pins Package EcoPlan(2) Lead/BallFinish MSLPeakTemp(3) Type Drawing Qty UC1572J OBSOLETE CDIP J 8 TBD CallTI CallTI UC2572D ACTIVE SOIC D 8 75 Green(RoHS& CUNIPDAU Level-1-260C-UNLIM noSb/Br) UC2572DG4 ACTIVE SOIC D 8 75 Green(RoHS& CUNIPDAU Level-1-260C-UNLIM noSb/Br) UC2572DTR ACTIVE SOIC D 8 2500 Green(RoHS& CUNIPDAU Level-1-260C-UNLIM noSb/Br) UC2572DTRG4 ACTIVE SOIC D 8 2500 Green(RoHS& CUNIPDAU Level-1-260C-UNLIM noSb/Br) UC2572N ACTIVE PDIP P 8 50 Green(RoHS& CUNIPDAU N/AforPkgType noSb/Br) UC2572NG4 ACTIVE PDIP P 8 50 Green(RoHS& CUNIPDAU N/AforPkgType noSb/Br) UC3572D ACTIVE SOIC D 8 75 Green(RoHS& CUNIPDAU Level-1-260C-UNLIM noSb/Br) UC3572DG4 ACTIVE SOIC D 8 75 Green(RoHS& CUNIPDAU Level-1-260C-UNLIM noSb/Br) UC3572DTR ACTIVE SOIC D 8 2500 Green(RoHS& CUNIPDAU Level-1-260C-UNLIM noSb/Br) UC3572DTRG4 ACTIVE SOIC D 8 2500 Green(RoHS& CUNIPDAU Level-1-260C-UNLIM noSb/Br) UC3572N ACTIVE PDIP P 8 50 Green(RoHS& CUNIPDAU N/AforPkgType noSb/Br) UC3572NG4 ACTIVE PDIP P 8 50 Green(RoHS& CUNIPDAU N/AforPkgType noSb/Br) (1)Themarketingstatusvaluesaredefinedasfollows: ACTIVE:Productdevicerecommendedfornewdesigns. LIFEBUY:TIhasannouncedthatthedevicewillbediscontinued,andalifetime-buyperiodisineffect. NRND:Notrecommendedfornewdesigns.Deviceisinproductiontosupportexistingcustomers,butTIdoesnotrecommendusingthispartin anewdesign. PREVIEW:Devicehasbeenannouncedbutisnotinproduction.Samplesmayormaynotbeavailable. OBSOLETE:TIhasdiscontinuedtheproductionofthedevice. (2)EcoPlan-Theplannedeco-friendlyclassification:Pb-Free(RoHS),Pb-Free(RoHSExempt),orGreen(RoHS&noSb/Br)-pleasecheck http://www.ti.com/productcontentforthelatestavailabilityinformationandadditionalproductcontentdetails. TBD:ThePb-Free/Greenconversionplanhasnotbeendefined. Pb-Free(RoHS):TI'sterms"Lead-Free"or"Pb-Free"meansemiconductorproductsthatarecompatiblewiththecurrentRoHSrequirements forall6substances,includingtherequirementthatleadnotexceed0.1%byweightinhomogeneousmaterials.Wheredesignedtobesoldered athightemperatures,TIPb-Freeproductsaresuitableforuseinspecifiedlead-freeprocesses. Pb-Free(RoHSExempt):ThiscomponenthasaRoHSexemptionforeither1)lead-basedflip-chipsolderbumpsusedbetweenthedieand package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible)asdefinedabove. Green(RoHS&noSb/Br):TIdefines"Green"tomeanPb-Free(RoHScompatible),andfreeofBromine(Br)andAntimony(Sb)basedflame retardants(BrorSbdonotexceed0.1%byweightinhomogeneousmaterial) (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incomingmaterialsandchemicals.TIandTIsuppliersconsidercertaininformationtobeproprietary,andthusCASnumbersandotherlimited Addendum-Page1

PACKAGE OPTION ADDENDUM www.ti.com 18-Sep-2008 informationmaynotbeavailableforrelease. InnoeventshallTI'sliabilityarisingoutofsuchinformationexceedthetotalpurchasepriceoftheTIpart(s)atissueinthisdocumentsoldbyTI toCustomeronanannualbasis. Addendum-Page2

PACKAGE MATERIALS INFORMATION www.ti.com 19-Apr-2008 TAPE AND REEL INFORMATION *Alldimensionsarenominal Device Package Package Pins SPQ Reel Reel A0(mm) B0(mm) K0(mm) P1 W Pin1 Type Drawing Diameter Width (mm) (mm) Quadrant (mm) W1(mm) UC2572DTR SOIC D 8 2500 330.0 12.4 6.4 5.2 2.1 8.0 12.0 Q1 UC3572DTR SOIC D 8 2500 330.0 12.4 6.4 5.2 2.1 8.0 12.0 Q1 PackMaterials-Page1

PACKAGE MATERIALS INFORMATION www.ti.com 19-Apr-2008 *Alldimensionsarenominal Device PackageType PackageDrawing Pins SPQ Length(mm) Width(mm) Height(mm) UC2572DTR SOIC D 8 2500 340.5 338.1 20.6 UC3572DTR SOIC D 8 2500 340.5 338.1 20.6 PackMaterials-Page2

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