TL3844

 TL284x, TL384xCURRENT-MODE PWM CONTROLLERS SLVS038E – JANUARY 1989 – REVISED DECEMBER 1999DOptimized for Off-Line and dc-to-dcDDDDDDDDDDDConvertersLow Start-Up Current (<1 mA)Automatic Feed-Forward CompensationPulse-by-Pulse Current LimitingEnhanced Load-Response CharacteristicsUndervoltage Lockout With HysteresisDouble-Pulse SuppressionHigh-Current Totem-Pole OutputInternally Trimmed Bandgap Reference500-kHz OperationError Amplifier With Low OutputResistanceDesigned to Be Interchangeable WithUC2842 and UC3842 SeriesD PACKAGE(TOP VIEW)COMPNCVFBNCISENSENCRT/CT1234567141312111098REFNCVCCVCOUTPUTGNDPOWER GROUNDNC – No internal connectionD-8 OR P PACKAGE(TOP VIEW)descriptionCOMPVFBISENSERT/CT12348765REFVCCOUTPUTGNDThe TL284x and TL384x series of controlintegrated circuits provide the features that arenecessary to implement off-line or dc-to-dc fixed-frequency current-mode control schemes with a minimumnumber of external components. Some of the internally implemented circuits are an undervoltage lockout(UVLO), featuring a start-up current of less than 1 mA, and a precision reference trimmed for accuracy at theerror amplifier input. Other internal circuits include logic to ensure latched operation, a pulse-width modulation(PWM) comparator (which also provides current-limit control), and a totem-pole output stage designed to sourceor sink high-peak current. The output stage, suitable for driving N-channel MOSFETs, is low when it is in theoff state.Major differences between members of these series are the UVLO thresholds and maximum duty-cycle ranges.Typical UVLO thresholds of 16 V (on) and 10 V (off) on the TLx842 and TLx844 devices make them ideally suitedto off-line applications. The corresponding typical thresholds for the TLx843 and TLx845 devices are 8.4 V (on)and 7.6 V (off). The TLx842 and TLx843 devices can operate to duty cycles approaching 100%. A duty-cyclerange of 0 to 50% is obtained by the TLx844 and TLx845 by the addition of an internal toggle flip-flop, whichblanks the output off every other clock cycle.The TL284x-series devices are characterized for operation from –40°C to 85°C. The TL384x-series devices arecharacterized for operation from 0°C to 70°C.Please be aware that an important notice concerning availability, standard warranty, and use in critical applications ofTexasInstruments semiconductor products and disclaimers thereto appears at the end of this data sheet.PRODUCTION DATA information is current as of publication date.Products conform to specifications per the terms of Texas Instrumentsstandard warranty. Production processing does not necessarily includetesting of all parameters.Copyright © 1999, Texas Instruments IncorporatedPOST OFFICE BOX 655303 DALLAS, TEXAS 75265•1SLVS038E – JANUARY 1989 – REVISED DECEMBER 1999TL284x, TL384xCURRENT-MODE PWM CONTROLLERS AVAILABLE OPTIONSPACKAGED DEVICESTASMALL OUTLINE(D)TL3842DTL3843DTL3844DTL3845DTL2842DTL2843DTL2844DTL2845DSMALL OUTLINE(D-8)TL3842D-8TL3843D-8TL3844D-8TL3845D-8TL2842D-8TL2843D-8TL2844D-8TL2845D-8PLASTIC DIP(P)TL3842PTL3843PTL3844PTL3845PTL2842PTL2843PTL2844PTL2845PCHIPFORMCHIP FORM(Y)TL3842YTL3843YTL3844YTL3845Y–––– 0°C to 70°C–40°C to 85°CThe D and D-8 packages are available taped and reeled. Add the suffix R to the device type (i.e.,TL3842DR or TL3842DR-8). Chip forms are tested at 25°C.functional block diagramVCC1234 V NOMGND9–+UVLO5-V REFENInternalBiasVrefGoodLogic14REF11VCRT/CT7OSC†TErrorAmplifier10OUTPUTPOWERGROUND8S2RRR 1VCurrent-SenseComparatorPWMLatchVFBCOMPISENSE315+–†The toggle flip-flop is present only in TL2844, TL2845, TL3844, and TL3845.Pin numbers shown are for the D Package.2POST OFFICE BOX 655303 DALLAS, TEXAS 75265• TL284x, TL384xCURRENT-MODE PWM CONTROLLERS SLVS038E – JANUARY 1989 – REVISED DECEMBER 1999absolute maximum ratings over operating free-air temperature range (unless otherwise noted)†Supply voltage (see Note 1) (ICC < 30 mA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self limitingAnalog input voltage range, VI (VFB and ISENSE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to 6.3 VOutput voltage, VO (OUTPUT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 VInput voltage, VI, (VC, D package only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 VSupply current, ICC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 mAOutput current, IO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±1 AError amplifier output sink current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 mAPackage thermal impedance, θJA (see Notes 2 and 3):D package . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86°C/WD-8 package . . . . . . . . . . . . . . . . . . . . . . . . . . 97°C/WP package . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85°C/WVirtual junction temperature range, TJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to 150°COutput energy (capacitive load) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 µJLead temperature, 1,6 mm (1/16 inch) from case for 10 seconds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260°CStorage temperature range, Tstg –65. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . °C to 150°C†Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, andfunctional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is notimplied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.NOTES:1.All voltages are with respect to the device GND terminal.2.Maximum power dissipation is a function of TJ(max), θJA, and TA. The maximum allowable power dissipation at any allowableambient temperature is PD = (TJ(max) – TA)/θJA. Operating at the absolute maximum TJ of 150°C can impact reliability.3.The package thermal impedance is calculated in accordance with JESD 51.recommended operating conditionsMINSupply voltage, VCC and VC‡Input voltage, VI, RT/CTInput voltage, VI, VFB and ISENSEOutput voltage, VO, OUTPUTOutput voltage, VO, POWER GROUND‡Supply current, externally limited, ICCAverage output current, IOReference output current, IO(ref)Oscillator frequency, foscOperating virtual junction temperature, TJOperating free-air temperature, TOperatingfreeairtemperatureTA‡These recommended voltages for VC and POWER GROUND apply only to the D package.TL284xTL384x0–400100000–0.1NOMMAX305.55.530125200–205001258570UNITVVVVVmAmAmAkHz°C°CPOST OFFICE BOX 655303 DALLAS, TEXAS 75265•3SLVS038E – JANUARY 1989 – REVISED DECEMBER 1999TL284x, TL384xCURRENT-MODE PWM CONTROLLERS electrical characteristics over recommended operating free-air temperature range, VCC = 15 V (seeNote 4), RT = 10 kΩ, CT = 3.3 nF (unless otherwise specified)reference sectionPARAMETEROutput voltageLine regulationLoad regulationTemperature coefficientof output voltageOutput voltagewith worst-case variationOutput noise voltageOutput-voltage long-term driftShort-circuit output current†All typical values are at TA = 25°C.NOTE 4:Adjust VCC above the start threshold before setting it to 15 V.VCC = 12 V to 25 V,f = 10 Hz to 10 kHz,IO = 1 mA to 20 mA4.9505–30–10025–180–30TESTCONDITIONSTEST CONDITIONSIO = 1 mA,VCC = 12 V to 25 VIO = 1 mA to 20 mATA = 25°CTL284xMINTYP†4.955660.2MAX5.0520250.45.14.82505–10025–180TL384xMINTYP†4.95660.2MAX5.120250.45.18UNITVmVmVmV/°CVµVmVmATA = 25°CAfter 1000 h at TA = 25°Coscillator sectionPARAMETEROscillator frequency (see Note 5)Frequency change with supply voltageFrequency change with temperaturePeak-to-peak amplitude at RT/CTTESTCONDITIONSTEST CONDITIONSTA = 25°CVCC = 12 V to 25 VTL284xMINTYP†47522501.7MAX5710TL384xMINTYP†47522501.7MAX5710UNITkHzHz/kHzHz/kHzV†All typical values are at TA = 25°C.NOTES:4.Adjust VCC above the start threshold before setting it to 15 V.5.Output frequency equals oscillator frequency for the TLx842 and TLx843. Output frequency is one-half oscillator frequency for theTLx844 and TLx845.error-amplifier sectionPARAMETERFeedback input voltageInput bias currentOpen-loop voltage amplificationGain-bandwidth productSupply-voltage rejection ratioOutput sink currentOutput source currentHigh-level output voltageLow-level output voltageVCC = 12 V to 25 VVFB at 2.7 V,COMP at 1.1 VVFB at 2.3 V,VFB at 2.3 V,VFB at 2.7 V,COMP at 5 VRL = 15 kΩ to GNDRL = 15 kΩ to GNDVO = 2 V to 4 V650.7602–0.55TESTCONDITIONSTEST CONDITIONSCOMP at 2.5 VTL284xMINTYP†2.452.50–0.3901706–0.860.71.1MAX2.55–1650.7602–0.55TL384xMINTYP†2.422.50–0.3901706–0.860.71.1MAX2.58–2UNITVµAdBMHzdBmAmAVV†All typical values are at TA = 25°C.NOTE 4:Adjust VCC above the start threshold before setting it to 15 V.4POST OFFICE BOX 655303 DALLAS, TEXAS 75265• TL284x, TL384xCURRENT-MODE PWM CONTROLLERS SLVS038E – JANUARY 1989 – REVISED DECEMBER 1999electrical characteristics over recommended operating free-air temperature range, VCC = 15 V (seeNote 4), RT = 10 kΩ, CT = 3.3 nF (unless otherwise specified) (continued)current-sense sectionPARAMETERVoltage amplificationCurrent-sense comparator thresholdSupply-voltage rejection ratioInput bias currentDelay time to outputTESTCONDITIONSTEST CONDITIONSSee Notes 6 and 7COMP at 5 V,VCC = 12 V to 25 V,See Note 6See Note 6TL284xMINTYP†2.850.93170–2150–10300MAX3.131.1TL384xMINTYP†2.850.93170–2150–10300MAX3.151.1UNITV/VVdBµAns†All typical values are at TA = 25°C.NOTES:4.Adjust VCC above the start threshold before setting it to 15 V.6.These parameters are measured at the trip point of the latch, with VFB at 0 V.7.Voltage amplification is measured between ISENSE and COMP, with the input changing from 0 V to 0.8 V.output sectionPARAMETERHighleveloutputvoltageHigh-level output voltageLowleveloutputvoltageLow-level output voltageRise timeFall timeTESTCONDITIONSTEST CONDITIONSIOH = –20 mAIOH = –200 mAIOL = 20 mAIOL = 200 mACL = 1 nF,CL = 1 nF,TA = 25°CTA = 25°CTL284xMINTYP†131213.513.50.11.550500.42.2150150MAXTL384xMINTYP†131213.513.50.11.550500.42.2150150MAXUNITVVnsns†All typical values are at TA = 25°C.NOTE 4:Adjust VCC above the start threshold before setting it to 15 V.undervoltage-lockout sectionPARAMETERStartthresholdvoltageStart threshold voltageMinimumoperatingvoltageafterstartupMinimum operating voltage after startupTLx842, TLx844TLx843, TLx845TLx842, TLx844TLx843, TLx845TL284xMINTYP†157.897168.4107.6MAX179118.2TL384xMINTYP†14.57.88.57168.4107.6MAX17.5911.58.2UNITVV†All typical values are at TA = 25°C.NOTE 4:Adjust VCC above the start threshold before setting it to 15 V.pulse-width-modulator sectionPARAMETERMaximumdutycycleMaximum duty cycleMinimum duty cycle†All typical values are at TA = 25°C.NOTE 4:Adjust VCC above the start threshold before setting it to 15 V.TLx842, TLx843TLx844, TLx845TL284xMINTYP†95%46%97%48%MAX100%50%0TL384xMINTYP†95%46%97%48%MAX100%50%0UNITPOST OFFICE BOX 655303 DALLAS, TEXAS 75265•5SLVS038E – JANUARY 1989 – REVISED DECEMBER 1999TL284x, TL384xCURRENT-MODE PWM CONTROLLERS electrical characteristics over recommended operating free-air temperature range, VCC = 15 V (seeNote 4), RT = 10 kΩ, CT = 3.3 nF (unless otherwise specified) (continued)supply voltagePARAMETERStart-up currentOperating supply currentLimiting voltageVFB and ISENSE at 0 VICC = 25 mATESTCONDITIONSTEST CONDITIONSTL284xMINTYP†0.51134MAX117TL384xMINTYP†0.51134MAX117UNITmAmAV†All typical values are at TA = 25°C.NOTE 4:Adjust VCC above the start threshold before setting it to 15 V.electrical characteristics, VCC = 15 V (see Note 4), RT = 10 kΩ, CT = 3.3 nF, TA = 25°C (unless otherwisespecified)reference sectionPARAMETEROutput voltageLine regulationLoad regulationTemperature coefficient of output voltageOutput noise voltageOutput-voltage long-term driftShort-circuit output currentNOTE 4:Adjust VCC above the start threshold before setting it to 15 V.f = 10 Hz to 10 kHzAfter 1000 h at TA = 25°CTESTCONDITIONSTEST CONDITIONSIO = 1 mAVCC = 12 V to 25 VIO = 1 mA to 20 mATL384xYMINTYP5660.2505–100MAXUNITVmVmVmV/°CµVmVmAoscillator sectionPARAMETEROscillator frequency (see Note 5)Frequency change with supply voltageFrequency change with temperaturePeak-to-peak amplitude at RT/CTVCC = 12 V to 25 VTESTCONDITIONSTEST CONDITIONSTL384xYMINTYP52251.7MAXUNITkHzHz/kHzHz/kHzVNOTES:4.Adjust VCC above the start threshold before setting it to 15 V.5.Output frequency equals oscillator frequency for the TLx842 and TLx843. Output frequency is one-half oscillator frequency for theTLx844 and TLx845.6POST OFFICE BOX 655303 DALLAS, TEXAS 75265• TL284x, TL384xCURRENT-MODE PWM CONTROLLERS SLVS038E – JANUARY 1989 – REVISED DECEMBER 1999electrical characteristics, VCC = 15 V (see Note 4), RT = 10 kΩ, CT = 3.3 nF, TA= 25°C (unless otherwisespecified) (continued)error-amplifier sectionPARAMETERFeedback input voltageInput bias currentOpen-loop voltage amplificationGain-bandwidth productSupply-voltage rejection ratioOutput sink currentOutput source currentHigh-level output voltageLow-level output voltageVCC = 12 V to 25 VVFB at 2.7 V,VFB at 2.3 V,VFB at 2.3 V,VFB at 2.7 V,COMP at 1.1 VCOMP at 5 VRL = 15 kΩ to GNDRL = 15 kΩ to GNDVO = 2 V to 4 VTESTCONDITIONSTEST CONDITIONSCOMP at 2.5 VTL384xYMINTYP2.50–0.3901706–0.860.7MAXUNITVµAdBMHzdBmAmAVVNOTE 4:Adjust VCC above the start threshold before setting it to 15 V.current-sense sectionPARAMETERVoltage amplificationCurrent-sense comparator thresholdSupply-voltage rejection ratioInput bias currentDelay time to outputNOTES:4.Adjust VCC above the start threshold before setting it to 15 V.6.These parameters are measured at the trip point of the latch, with VFB at 0 V.7.Voltage amplification is measured between ISENSE and COMP, with the input changing from 0 V to 0.8 V.TESTCONDITIONSTEST CONDITIONSSee Notes 6 and 7COMP at 5 V,VCC = 12 V to 25 V,See Note 6See Note 6TL384xYMINTYP3170–2150MAXUNITV/VVdBµAnsoutput sectionPARAMETERHighleveloutputvoltageHigh-level output voltageLowleveloutputvoltageLow-level output voltageRise timeFall timeTESTCONDITIONSTEST CONDITIONSIOH = –20 mAIOH = –200 mAIOL = 20 mAIOL = 200 mACL = 1 nFCL = 1 nFTL384xYMINTYP13.513.50.11.55050MAXUNITVVnsnsNOTE 4:Adjust VCC above the start threshold before setting it to 15 V.undervoltage-lockout sectionPARAMETERStartthresholdvoltageStart threshold voltageMinimumoperatingvoltageafterstartupMinimum operating voltage after startupNOTE 4:Adjust VCC above the start threshold before setting it to 15 V.TL3842Y, TL3844YTL3843Y, TL3845YTL3842Y, TL3844YTL3843Y, TL3845YTL384xYMINTYP168.4107.6MAXUNITVVPOST OFFICE BOX 655303 DALLAS, TEXAS 75265•7SLVS038E – JANUARY 1989 – REVISED DECEMBER 1999TL284x, TL384xCURRENT-MODE PWM CONTROLLERS electrical characteristics, VCC = 15 V (see Note 4), RT = 10 kΩ, CT = 3.3 nF, TA = 25°C (unless otherwisespecified) (continued)pulse-width-modulator sectionPARAMETERMaximumdutycycleMaximum duty cycleNOTE 4:Adjust VCC above the start threshold before setting it to 15 V.TL3842Y, TL3843YTL3844Y, TL3845YTL384xYMINTYP97%48%MAXUNITsupply voltagePARAMETERStart-up currentOperating supply currentLimiting voltageVFB and ISENSE at 0 VICC = 25 mANOTE 4:Adjust VCC above the start threshold before setting it to 15 V.TESTCONDITIONSTEST CONDITIONSTL384xYMINTYP0.51134MAX117UNITmAmAV8POST OFFICE BOX 655303 DALLAS, TEXAS 75265• TL284x, TL384xCURRENT-MODE PWM CONTROLLERS SLVS038E – JANUARY 1989 – REVISED DECEMBER 1999APPLICATION INFORMATION2.5 VErrorAmplifierZiZfVFB+–0.5 mACOMPNOTE A: Error amplifier can source or sink up to 0.5 mA.Figure 1. Error-Amplifier ConfigurationIS(see Note A)ErrorAmplifier+–2RR 1VCOMPCurrent-SenseComparatorRfISENSECfGNDRSNOTE A:Peak current (IS) is determined by the formula:IS(max)+1VRSA small RC filter formed by resistor Rf and capacitor Cf may be required to suppress switch transients.Figure 2. Current-Sense CircuitREFRT(see Note A)RT/CTCTGNDNOTE A:For RT > 5 kΩ:f[1.72RTCTFigure 3. Oscillator SectionPOST OFFICE BOX 655303 DALLAS, TEXAS 75265•9SLVS038E – JANUARY 1989 – REVISED DECEMBER 1999TL284x, TL384xCURRENT-MODE PWM CONTROLLERS APPLICATION INFORMATIONDEAD TIMEvsTIMING CAPACITANCE10040VCC = 15 VRT ≥ 5 kΩTA = 25°C40RT– Timing Resistance – kΩ104 TIMING RESISTANCEvsFREQUENCY100CT = 10 nFCT = 4.7 nFCT = 22 nFCT = 1 nFDead Time –µs10CT = 22 nFCT = 47 nF10.44CT = 100 nF0.10410401001100VCC = 15 VTA = 25°C1 k10 kf - Frequency - Hz100 k1 MCT – Timing Capacitance – nFFigure 4Figure 5open-loop laboratory test fixtureIn the open-loop laboratory test fixture shown in Figure 6, high peak currents associated with loads necessitatecareful grounding techniques. Timing and bypass capacitors should be connected close to the GND terminalin a single-point ground. The transistor and 5-kΩ potentiometer sample the oscillator waveform and apply anadjustable ramp to the ISENSE terminal.REFRT4.7 kΩ2N2222100 kΩ1 kΩError AmplifierAdjust5 kΩ4.7 kΩISENSEAdjustDUTCOMPVFBISENSERT/CTTL284xTL384xVCCOUTPUTGNDGNDCT0.1 µF1 kΩ, 1 WOUTPUTREF0.1 µFAVCCFigure 6. Open-Loop Laboratory Test Fixture10POST OFFICE BOX 655303 DALLAS, TEXAS 75265• TL284x, TL384xCURRENT-MODE PWM CONTROLLERS SLVS038E – JANUARY 1989 – REVISED DECEMBER 1999APPLICATION INFORMATIONshutdown techniqueThe PWM controller (see Figure 7) can be shut down by two methods: either raise the voltage at ISENSE above1 V or pull the COMP terminal below a voltage two diode drops above ground. Either method causes the outputof the PWM comparator to be high (refer to block diagram). The PWM latch is reset dominant so that the outputremains low until the next clock cycle after the shutdown condition at the COMP or ISENSE terminal is removed.In one example, an externally latched shutdown can be accomplished by adding an SCR that resets by cyclingVCC below the lower UVLO threshold. At this point, the reference turns off, allowing the SCR to reset.1 kΩREFCOMPShutdown330 ΩShutdown500 ΩTo Current-SenseResistorISENSEFigure 7. Shutdown TechniquesA fraction of the oscillator ramp can be resistively summed with the current-sense signal to provide slopecompensation for converters requiring duty cycles over 50% (see Figure 8). Note that capacitor C forms a filterwith R2 to suppress the leading-edge switch spikes.REF0.1 µFRTRT/CTCTR1R2ISENSECRSENSEISENSEFigure 8. Slope CompensationPOST OFFICE BOX 655303 DALLAS, TEXAS 75265•11IMPORTANT NOTICE

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