高性能电流模式PWM控制器MXT7111.pdf

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1、MXT7111 is offered in SOT23-6 packages.MXT7111 offers complete protection coverage with converter applications in sub 36W range.MXT7111.A large value resistMXT7111 is a highly int Confidential Current Mode PWM Power SwitchProduct SpecificationFreq Shuffling GENERAL DESCRIPTION egrated current mode P

2、WM control IC optimized for high performance,low standby power and cost effective offline flyback PWM switching frequency at normal operation is externally programmable and trimmed to tight range.At no load or light load condition,the IC operates in extendedburst modeto minimize switching loss.Lower

3、 standby power and higher conversion efficiency is thus achieved.VDD low startup current and low operating current contribute to a reliable power on startup design with or could thus be used in the startup circuit to minimize the standby power.The internal slope compensation improves system large si

4、gnal stability and reduces the possible subharmonic oscillation at high PWM duty cycle output.Leading-edge blanking on current sense(CS)input removes the signal glitch due to snubber circuit diode reverse recovery and thus greatly reduces the external component count and system cost in the design.au

5、tomatic self-recovery feature including Cycle-by-Cycle current limiting(OCP),over load protection(OLP),VDD over voltage clamp and under voltage lockout(UVLO).The Gate-drive output is clamped to maximum 18V to protect the power MOSFET.Excellent EMI performance is achieved with Power-Source proprietar

6、y frequency shuffling technique together with soft switching control at the totem polegate drive output.Tone energy at below 20KHZ is minimized in the design and audio noise is eliminated during operation.FEATURES Level 5 compliance with 100mW standby power at universal AC input.Power Source Proprie

7、tary Frequency Shuffling Technology for Improved EMI Performance.Extended Burst Mode Control For Improved Efficiency and Minimum Standby Power Design Audio Noise Free Operation External Programmable PWM Switching Frequency Internal Synchronized Slope Compensation Low VDD Startup Current and Low Oper

8、ating Current(1.4mA)Leading Edge Blanking on Current Sense Input Good Protection Coverage With Auto Self-Recovery o VDD Over Voltage Clamp and Under Voltage Lockout with Hysteresis(UVLO)o Gate Output Maximum Voltage Clamp(18V)o Power Source Proprietary Line Input Compensated Cycle-by-Cycle Over-curr

9、ent Threshold Setting For Constant Output Power Limiting Over Universal Input Voltage Range.o Overload Protection(OLP)APPLICATIONS Offline AC/DC flyback converter for Battery Charger Power Adaptor Set-Top Box Power Supplies Open-frame SMPS TYPICAL APPLICATION MXT71111MXTMXT71117111:Product Name X:Lo

10、t Number Code 7 111SX The MXT7111 is offered in SOT23-6 packages,2 GENERAL INFORMATION Pin Configuration shown as below.Package Dissipation Rating Package RJA(/W)SOT23-6 200 Absolute Maximum Ratings Parameter Value VDD DC Supply Voltage 30 V VDD Zener Clamp VoltageNote VDD_Clamp+0.1V VDD DC Clamp Cu

11、rrent 10 mA VFB Input Voltage-0.3 to 7V VSENSE Input Voltage to Sense Pin-0.3 to 7V VRI Input Voltage to RI Pin-0.3 to 7V Min/Max Operating Junction Temperature TJ-20 to 150 oC Min/Max Storage Temperature Tstg-55 to 160 oC Note:VDD_Clamp has a nominal value of 34V.Stresses beyond those listed under“

12、absolute maximum ratings”may cause permanent damage to the device.These are stress ratings only,functional operation of the device at these or any other conditions beyond those indicated under“recommended operating conditions”is not implied.Exposure to absolute maximum-rated conditions for extended

13、periods may affect device reliability.Marking Information TERMINAL ASSIGNMENTS Pin Name I/O Description GND P Ground FB I Feedback input pin.The PWM duty cycle is determained by voltage level into this pin and SENSE pin input.RI I Internal Oscillator frequency setting pin.A resistor connected betwee

14、n RI and GND sets the PWM frequency.SENSE I Current sense input pin.Connected to MOSFET current sensing resistor node.VDD P Chip DC power supply pin.GATE O Totem-pole gate drive output for the power MOSFET.123 4 5 6 GND FB RI SENSE VDD GATE Current Mode PWM Power SwitchProduct SpecificationFreq Shuf

15、flingMXT7111Confidential MXTS:Package 3 RECOMMENDED OPERATING CONDITION Symbol Parameter Min/Max Unit VDD VDD Supply Voltage 10 to 30 V RI RI Resistor Value 100 Kohm TA Operation Ambient Temperature-20 to 85 BLOCK DIAGRAM Current Mode PWM Power SwitchProduct SpecificationFreq ShufflingMXT7111Confide

16、ntial MXT4 ELECTRICAL CHARACTERISTICS(TA=25 if not otherwise noted)Symbol Parameter Test Conditions Min Typ Max Unit Supply Voltage(VDD)I_VDD_Startup VDD Start up Current VDD=12.5V,RI=100K Measure Leakage current into VDD 3 20 uA I_VDD_Ops Operation Current VDD=16V,RI=100K,VFB=3V 1.4 mA UVLO(ON)VDD

17、Under Voltage Lockout Enter 6.2 7.2 8.2 V UVLO(OFF)VDD Under Voltage Lockout Exit(Recovery)13 14 15 V VDD_Clamp VDD Zener Clamp Voltage IVDD=5mA 34 V Feedback Input Section(FB Pin)AVCS PWM Input Gain VFB/VCS 2.0 V/V VFB_Open VFB Open Loop Voltage 4.8 V IFB_Short FB pin short circuit current Short FB

18、 pin to GND and measure current 1.0 mA VTH_0D Zero Duty Cycle FB Threshold Voltage VDD=16V,RI=100K 0.75 V VTH_PL Power Limiting FB Threshold Voltage 3.7 V TD_PL Power Limiting Debounce Time 35 mSecZFB_IN Input Impedance 6 KohmDC_MAX Maximum Duty Cycle VDD=18V,RI=100K,FB=3V,CS=0V 75%Current Sense Inp

19、ut(Sense Pin)T_blanking Leading edge blanking time RI=100K 300 ns ZSENSE_IN Input Impedance 40 KohmTD_OC Over Current Detection and Control Delay VDD=16V,CSVTH_OC,FB=3.3V 75 nSecVTH_OC Over Current Threshold Voltage at zero Duty Cycle FB=3.3V,RI=100K 0.70 0.75 0.80 V Oscillator FOSC Normal Oscillati

20、on Frequency RI=100K 60 65 70 KHz f_Temp Frequency Temperature Stability VDD=16V,RI=100K,TA-20 to 100 5%f_VDD Frequency Voltage Stability VDD=12-25V,RI=100K 5%RI_range Operating RI Range 50 100 150 KohmV_RI_open RI open load voltage 2 V FOSC_BM Burst Mode Base Frequency VDD=16V,RI=100K 22 KHz Curren

21、t Mode PWM Power SwitchProduct SpecificationFreq ShufflingMXT7111Confidential MXT5 Symbol Parameter Test Conditions Min Typ Max Unit Gate Drive Output VOL Output Low Level VDD=16V,IO=-20mA 0.8 V VOH Output High Level VDD=16V,IO=20mA 10 V V_Clamp Output Clamp Voltage Level 18 V T_r Output Rising Time

22、 VDD=16V,CL=1nF 220 nSecT_f Output Falling Time VDD=16V,CL=1nF 70 nSecFrequency Shuffling f_OSC Frequency Modulation range/Base Frequency RI=100K-3 3%f_shuffling Shuffling Frequency RI=100K 64 Hz Current Mode PWM Power SwitchProduct SpecificationFreq ShufflingMXT7111Confidential MXT6 CHARACTERIZATIO

23、N PLOTS VDD=16V,RI=100Kohm,TA=25 condition applies if not otherwise noted.Current Mode PWM Power SwitchProduct SpecificationFreq ShufflingMXT7111Confidential MXT7 Current Mode PWM Power SwitchProduct SpecificationFreq ShufflingMXT7111Confidential MXTapplications in sub 36W power range.The extended T

24、he MXT7111 is a highly in8 OPERATION DESCRIPTION tegrated PWM controller IC optimized for offline flyback converter burst mode control greatly reduces the standby power consumption and helps the design easily meet the international power conservation requirements.Startup Current and Start up Control

25、 so that VDD could be charged up above UVLO threshold level and device starts up quickly.A large value startup resistor can therefore be used to minimize the power loss yet provides reliable startup in application.For AC/DC adaptor with universal input range design,a 2 M,1/8 W startup resistor could

26、 be used together with a VDD capacitor to provide a fast startup and low power dissipation solution.Operating Current operating current together with extended burst mode control features.Frequency shuffling for EMI improvement The frequency Shuffling/jittering(switching The oscillation frequency is

27、modulated with a random source so that the tone energy is spread out.The spread spectrum minimizes the conduction band EMI and therefore reduces system design challenge.Extended Burst Mode Operation At zero load or light load condition,majority of the power dissipation in a switching mode power supp

28、ly is from switching loss on the MOSFET transistor,the core loss of the transformer and the loss on the snubber circuit.The magnitude of power loss is in proportion to the number of switching events within a fixed period of time.Reducing switching events leads to the reduction on the power loss and

29、thus conserves the energy.the loading condition.At from no load to light/medium load condition,the FB input drops below burst mode threshold level.Device enters Burst Mode control.The Gate drive output switches only when VDD voltage drops below a preset level and FB input is active to output an on s

30、tate.Otherwise the gate drive remains at off state to minimize the switching loss and reduces the standby power consumption to the greatest extend.The frequency control also eliminates the audio noise at any loading conditions.Oscillator Operation A resistor connected between RI and GND sets the con

31、stant current source to charge/discharge the internal cap and thus the PWM oscillator frequency is determined.The relationship between RI and switching frequency follows the below equation within the specified RI in Kohm range at nominal loading operational condition.6500()(ohm)OSCFKHzRI K Current S

32、ensing and Leading Edge Blanking Cycle-by-Cycle current limiting is offered in current is detected by a sense resistor into the sense pin.An internal leading edge blanking circuit chops off the sense voltage spike at initial MOSFET on state due to Snubber diode reverse recovery so that the external

33、RC filtering on sense input is no longer required.The current limit comparator is disabled and thus cannot turn off the external MOSFET during the blanking period.PWM duty cycle is determined by the current sense input voltage and the FB input voltage.Internal Synchronized Slope Compensation Built-i

34、n slope compensation circuit adds voltage ramp onto the current sense input voltage for PWM generation.This greatly improves the close loop stability at CCM and prevents the sub-harmonic oscillation and thus reduces the output ripple voltage.Gate Drive gate for power switch control.Too weak the gate

35、 drive strength results in higher conduction and switch loss of MOSFET while too strong gate drive output compromises the EMI.A good tradeoff is achieved through the built-in totem pole gate design with right output strength and dead time control.The low idle loss and good EMI system design is easie

36、r to achieve with this dedicated control scheme.An internal 18V clamp is added for MOSFET gate protection at higher than expected VDD input.Current Mode PWM Power SwitchProduct SpecificationFreq ShufflingMXT7111Confidential MXTStartup current of MXT7111 is designed to be very low The Operating curre

37、nt of MXT7111 is low at 1.4mA.frequency modulation)is implemented in MXT7111.MXT7111 self adjusts the switching mode according to Good efficiency is achieved with MXT7111 low MXT7111 current mode PWM control.The switch MXT7111 Gate is connected to an external MOSFET 9 Protection Controls Good power

38、supply system reliability is achieved with its rich protection features including Cycle-by-Cycle current limiting(OCP),Over Load Protection(OLP)and over voltage clamp,Under Voltage Lockout on VDD(UVLO).With Power Source Proprietary technology,the OCP threshold tracks PWM Duty cycles and is line volt

39、age compensated to achieve constant output power limit over the universal input voltage range with recommended reference design.At overload condition when FB input voltage exceeds power limit threshold value for more than TD_PL,control circuit reacts to shut down the output power MOSFET.Device resta

40、rts when VDD voltage drops below UVLO limit.VDD is supplied by transformer auxiliary winding output.It is clamped when VDD is higher than threshold value.The power MOSFET is shut down when VDD drops below UVLO limit and device enters power on start-up sequence thereafter.Current Mode PWM Power Switc

41、hProduct SpecificationFreq ShufflingMXT7111Confidential MXT10 PACKAGE MECHANICAL DATA SOT23-6 Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 1.050 1.250 0.041 0.049 A1 0.000 0.100 0.000 0.004 A2 1.050 1.150 0.041 0.045 b 0.300 0.400 0.012 0.016 c 0.100 0.200 0.004 0.008 D 2.820 3.020 0.111 0.119 E 1.500 1.700 0.059 0.067 E1 2.650 2.950 0.104 0.116 e 0.950Typ 0.037Typ e1 1.800 2.000 0.071 0.079 L 0.700Ref 0.028Ref L1 0.300 0.600 0.012 0.024 0 8 0 8 Current Mode PWM Power SwitchProduct SpecificationFreq ShufflingMXT7111Confidential MXT