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| Page No. : 1/12 AX3842P / AX3842S High Performance Current Mode Pwm Controlers Description The AX3842 Series is high performance fixed frequency current mode controllers. That is specifically designed for Off-Line and DC To DC converter applications offering the designer a costeffective solution with minimal external components. These integrated circuits feature a trimmed oscillator for precise duty cycle control. A temperature compensated reference, high gain error amplifier, current sensing compara-tor, and a high current totem pole output ideally suited for driving a power MOSFET. Also included are protective features consisting of input and reference undervoltage lockouts each with hysteresis, cycle-by-cycle current limiting, programmable output deadtime, and a latch for single pulse metering. 8-Lead Plastic DIP-8 Package Code: P * 8-Lead Plastic SO-8 Package Code: S Features * Trimmed Oscillator for Precise Frequency Control * Oscillator Frequency Guaranteed at 250 kHz * Current Mode Operation to 500 kHz * Automatic Feed Forward Compensation * Latching PWM for Cycle-By-Cycle Current Limiting * Internally Trimmed Reference with Undervoltage Lockout * High Current Totem Pole Output * Undervoltage Lockout with Hysteresis * Low Startup and Operating Current Absolute Maximum Ratings Symbol Vi Vi IO EO Parameter Supply Voltage (low impedance source) Supply Voltage (Ii<30mA) Output Current Output Energy (capacitive load) Analog Inputs (pin 2, 3) Error Amplifier Output Sink Current Ptot Tstg TJ TL Power Dissipation at Tamb25oC Storage Temperature Range Junction Operating Temperature Lead Temperature (soldering 10s) Value 30 Self Limiting 1 5 -0.3 to 5.5 10 800 -65 to 150 -40 to 150 300 A uJ V mA mW o o o Unit V C C C Thermal Data Symbol Rth j-amb Description Thermal Resistance Junction-ambient DIP-8 100 SO-8 150 Units o C/W AVANTICS - AX3842 Series Specification No.: 050308-FE0008 Page No. : 2/12 Block Diagram Vcc 7 34V UVLO S/R 5V REF Internal Bias VREF Good Logic T 2R R S R 1V Current Sense Comparator 6 8 VREF 5V 50mA Ground 5 2.50V RT/CT 4 Error AMP. + - OSC Output VFB COMP Current Sense 2 1 3 PWM Latch Pin Connection (Top View) Package Function Pin1: Compensation 8 7 6 5 Description This pin is the Error Amplifier output and is made available for loop compensation. This is the inverting input of the Error Amplifier. It's normally connected to the switching power supply output through a resistor divider. A voltage proportional to inductor current is connected to this input. The PWM uses this information to terminate the output switch conduction. The oscillator frequency and maximum output duty cycle are programmed by connecting resistor RT to Vref and cpacitor CT to ground. Operation to 500kHz is possible. This pin is the combined control circuitry and power ground. This output directly drives the gate of a power MOSFET. Peak currents up to 1A are sourced and sunk by this pin. This pin is the positive supply of the control IC. This is the reference output. It provides charging current for capacitor CT through resistor RT. Pin2: Voltage Feedback 1 2 3 4 Pin3: Current Sense DIP-8 8 7 6 5 Pin4: RT/CT Pin5: Ground 1 2 3 4 Pin6: Output Pin7: Vcc Pin8: Vref SO-8 AVANTICS - AX3842 Series Specification No.: 050308-FE0008 Page No. : 3/12 Electrical Characteristics Unless otherwise stated, specifications apply for 0Tamb70C VCC=15V (Note 1); RT=680, CT=0.022uF for triangular mode, RT=10k, CT=3.3nf for sawtooth mode Symbol Reference Section VREF VREF VREF Parameter Reference Output Voltage Line Regulation Load Regulation Total Output Variation Test Conditions Tj=25C,Io=1mA 12VVin25V 1mAIo20mA (Note 2) Min. 4.90 - Typ. 5 2.0 3.0 0.2 50 5 -100 52 52 0.2 5 0.5 1.7 8.3 2.50 -0.1 90 1.0 70 12 -1.0 6 0.7 3.0 1.0 70 -2.0 150 Max. 5.1 20 25 5.18 -180 57 60 1 9.3 9.5 2.58 -2.0 1.1 3.15 1.1 -10 300 Units V mV mV mV/C V uV mV mA KHz KHz % % % V mA mA V uA dB MHz dB mA mA V V V/V V dB uA nS VREF/T Temperature Stability eN ISC Output Noise Voltage Long Term Stability Output Short Current Oscillator Section fOSC fOSC/V fOSC/T VOSC Idischg Frequency Frequency Change with Volt. Frequency Change with Temp. Oscillator Voltage Swing Discharge Current (VOSC=2V) Line, Load, Temp (Note 2) (Note 2) 4.82 -30 47 46 7.8 7.2 2.42 65 0.7 60 2.0 -0.5 5 2.85 10Hzf10kHz,Tj=25C Ta=25C TJ=25C TlowTAThigh 12VVCC25V TlowTAThigh TJ=25C Peak to Peak TJ=25C TlowTAThigh VO=2.5V VFB=5.0V 2VO4 V TJ=25C (Note 2) 12VVCC25V (Note 2) Ta=125C,1000Hrs (Note 2) Error Amplifier Section V2 Ib AVOL BW PSRR IO VOUT-High VOUT-Low GV V3 SVR Ib Voltage Feedback Input Input Bias Current Open Loop Voltage Gain Unity Gain Bandwidth Power Supply Rejection Ratio Output Current Output Voltage Swing High State Output Voltage Swing Low State Current Sense Input Voltage Gain Maximum Input Signal Supply Voltage Rejection Ratio Input Bias Current Propagation Delay Tj=25C (Note 2) Sink (VO=1.1V, VFB=2.7V) Source (VO=5.0V, VFB=2.3V) VFB=2.3V, RL=15K to ground VFB=2.7V, RL=15K to VREF (Notes 3 & 4) Current Sense Section VPIN1=5V (Note 3) (Note 3) 0.9 - 12VVCC25V AVANTICS - AX3842 Series Specification No.: 050308-FE0008 Page No. : 4/12 Electrical Characteristics (continued) Symbol Output Section VOL VOH VOLS tr tf Output Voltage (Low State) Output Voltage (High State) Output Voltage with UVLO Activated Output Voltage Rise Time Output Voltage Fall Time Start Threshold Min. Operating Voltage PWM Section DCmax DCmin Ist Ii Viz Maximum Duty Cycle Minimum Duty Cycle Start-Up Current Operating Supply Current Vcc Zener Voltage Vpin2=Vpin3=0, RT=10K, CT=3.3nF ICC=25 mA 94 96 0.1 11 34 0 0.5 17 % % mA mA V After Turn On Isink=20mA Isink=200mA Isource=20mA Isource=200mA VCC=6V, Isink=1mA TJ=25C, CL=1.0nF (Note 2) TJ=25C, CL=1.0nF (Note 2) Parameter Test Conditions Min. 13 12 14.5 8.5 Typ. 0.1 1.5 13.5 13.4 -0.1 50 50 16 10 Max. 0.4 2.2 -1.1 150 150 17.5 11.5 Units V V V V V nS nS V V Under-Voltage Lockout Section Total Device Note 1: Adjust VCC above the start threshold before setting at 15V. Note 2: These parameters, although guaranteed are not 100% tested in production. Note 3: Parameter measured at trip point of latch with Vpin2=0. Note 4: Gain defined as: A=Vpin1/Vpin3, 0Vpin30.8V AVANTICS - AX3842 Series Specification No.: 050308-FE0008 Page No. : 5/12 Characteristics Curve Oscillator Frequency & Timing Resistance 10000K 100 Maximum Duty Cycle & Timing Resistance 80 1000K CT=1.0nF CT=2.2nF fo(Hz) CT=4.7nF 100K DCmax (%) 60 40 10K 20 1K 100 1000 10000 100000 0 100 1000 10000 100000 RT() RT() Oscillator Discharge Current & Temperate 9 100 Vi=15V Vosc=2V 80 Error Amp Open-Loop Gain and Phase & Frequency Vcc=15V Vo=2V to 4V RL=100K o Ta=25 C 30 60 Phase 90 120 150 180 10 100 1000 10000 100000 1000000 10000000 8.5 Gain 60 Idischg (mA) (dB) -50 -25 0 25 o 8 40 20 7.5 0 7 50 75 100 125 -20 TA ( C) f (Hz) Current Sense Input Threshold & Error Amp Output Voltage 1.2 Vcc=15V 1 Reference Voltage Change & Source Current 60 50 Vcc=15V 40 0.8 Vth (V) 0.6 0.4 0.2 0 0 Ta=25 C Ta=125 C o o 30 Ta=-40 C o 20 Ta=125 C 10 o Ta=25 C o Ta=-40 C o 0 2 4 6 8 0 20 40 60 80 100 120 Vo (V) Iref (mA) AVANTICS - AX3842 Series Specification No.: 050308-FE0008 Page No. : 6/12 Reference Short Circuit Current &Temperature 110 25 Supply Current & Supply Voltage 100 Vcc=15V RL0.1 20 RT=10K CT=3.3nF 90 Isc (mA) 15 80 Ii (mA) 10 5 0 -50 -25 0 25 0 70 60 50 TA ( C) o 50 75 100 125 10 20 30 40 Vi (V) Output Saturation Voltage & Load Current 0 Source Saturation (Load to Ground) -1 Ta=25 C o Output Saturation Voltage & Load Current 4 Sink Saturation (Load to Vcc) 3 Vsat (V) Vsat (V) Ta=-40 C 2 Ta=25 C o o -2 Ta=-40 C o -3 Vcc=15V 80us Pulsed Load 120Hz Rate 1 Vcc=15V 80us Pulsed Load 120Hz Rate -4 0 200 0 Io (mA) 400 600 800 0 200 Io (mA) 400 600 800 AVANTICS - AX3842 Series Specification No.: 050308-FE0008 Page No. : 7/12 Application Information Open Loop Test Circuit Vref 4.7K HPN2222A 100K Error Amp. Adjust 1K COMP VFB I SENSE Adjust I SENSE 5K RT/CT 1 2 3 4 AX3842 RT VREF 8 7 6 5 0.1uF Vcc Output Ground 0.1uF 1W 1K Output A Vcc 4.7K Ground CT High peak currents associated with capacitive loads necessitate careful grounding techniques. Timing and bypass capacitors should be connected close to pin5 in a single point ground. The transistor and 5K potentiometerare used to samplethe oscillator waveform and apply an adjustable ramp to pin3. Oscillator and Output Waveforms Vcc 7 8 PWM RT 4 Id CT CT 5 GND Output Small RT / Large CT Clock Oscillator 5V REG 1 2 3 CT 6 Output Output Large RT / Small CT Error Amp Configuration Under Voltage Lockout 2.5V + V FB 2 COMP 1 Zf 1mA Vi 7 ON/OFF Command To Rest Of IC Icc Zi Von Voff <17mA AX3842 16V 10V <0.5mA Voff Von Vcc AVANTICS - AX3842 Series Specification No.: 050308-FE0008 Page No. : 8/12 Current Sense Circuit Error Ampl. Is R Rs C Current Sense 5 GND COMP 1 3 R 1V 2R Current Sense Comparator Peak current (Is) is determined by the formula Is(max.) 1V/Rs A small RC filter may be required to suppress switch transients. Slope Compensation Techniques VREG RT RT/CT Is R SLOPE R1 Rs CT ISENSE 8 RT 4 AX3842 3 VREG 8 RT/CT Is R SLOPE R1 GND Rs CT ISENSE 5 4 AX3842 3 5 GND Isolated MOSFET Drive and Current Transformer Sensing Vcc 7 5.0Vref + Vin - Isolation Boundary Q1 VGS Waveforms + 0 50%DC 3 C R Rs Ns Np + 0 25%DC Ipk=((Vpin1-1.4)/3Rs)(Ns/Np) + S R + Q 6 COMP/Latch AVANTICS - AX3842 Series Specification No.: 050308-FE0008 Page No. : 9/12 Latched Shutdown 4 8 R R + + 1mA 2 1 2R EA R 5 2N3905 2N3903 BIAS OSC SCR must be selected for a holding current of less than 0.5mA at TA(min). The simple two transistor circuit can be used in place of the SCR as shown. All resistors are 10K. Error Amplifier Compensation From Vo Ri Rd Cf Rf 2.5V + EA + 1mA 2R R 5 + + EA 1mA 2R R 5 2 1 Error Amp compensation circuit for stabilizing any current-mode topology except for boost and flyback converters operating with continuous inductor current From Vo Rp Cp Ri Rd Cf Rf 2.5V 2 1 Error Amp compensation circuit for stabilizing current-mode boost and flyback topologies operating with continuous inductor current. External Clock Synchronization Vref 8 R RT R 4 CT External Sync Input 0.01uF 47 2 1 + EA 5 + BIAS OSC 2R R The diode clamp is required if the Sync amplitude is large enough to cause the bottom side of CT to go more than 300mV below ground Specification No.: 050308-FE0008 AVANTICS - AX3842 Series Page No. : 10/12 External Duty Cycle Clamp and Multi Unit Synchronization Vref RA RB 8 8 6 5 5K + 2 C 5K 1 NE555 1 To Additional AX3842 S 2 5K + R Q 3 7 4 + + EA 2R 5 R 4 R BIAS R OSC f=1.44/((RA+2RB)C), Dmax=RB/(RA+2RB) Soft-Start Circuit 8 R BIAS R 4 + + 2 1M C 1 5 EA 1mA 2R + R 1V R OSC S Q 5Vref + - Soft-Start and Error Amplifier Output Duty Cycle Clamp 7 8 R R 4 + + 2 R2 C R1 1 EA 1mA BIAS OSC Vclamp 2R R 5 BC109 1V + S Q R Comp/Latch + Vcc Vin 5Vref + - 7 6 Q1 5 Rs Vclamp=R1/(R1+R2) where 0 Page No. : 11/12 DIP-8 Dimension Marking: 8 7 6 5 Pb Free Mark Pb-Free: " . " Normal: None (Note) DIM A AX 3842 P Min. 6.29 9.22 3.25 3.17 0.38 2.28 7.49 8.56 0.229 94o Max. 6.40 9.32 *1.52 *1.27 *0.99 3.35 3.55 0.53 2.79 7.74 *3.00 8.81 0.381 97o A 1 2 3 4 B C D Control Code Date Code B F E F G H I J K L M 1 J Note: Green label is used for pb-free packing Pin Style: 1.COMP 2.VFB 3.ISENSE 4.RT/CT 5.GND 6.Output 7.Vi 8.VREF Material: * Lead solder plating: Sn60/Pb40 (Normal), Sn/3.0Ag/0.5Cu or Pure-Tin (Pb-free) * Mold Compound: Epoxy resin family, flammability solid burning class: UL94V-0 C E D G H 1 K M L I 8-Lead DIP-8 Plastic Package AVANTICS Package Code: P *: Typical, Unit: mm SO-8 Dimension A G Marking: Pb Free Mark Pb-Free: " . " (Note) A X Normal: None 8 B 7 6 5 C 4 J H I S 3842 Control Code Pin1 Index Pin 1 Index Date Code 2 3 Note: Green label is used for pb-free packing Pin Style: 1.COMP 2.VFB 3.ISENSE 4.RT/CT 5.GND 6.Output 7.Vi 8.VREF D E Part A K L N O Part A M Material: * Lead solder plating: Sn60/Pb40 (Normal), Sn/3.0Ag/0.5Cu or Pure-Tin (Pb-free) * Mold Compound: Epoxy resin family, flammability solid burning class: UL94V-0 DIM A B C D E F G H I J K L M N O Min. 4.85 3.85 5.80 1.22 0.37 3.74 1.45 4.80 0.05 0.30 0.19 0.37 0.23 0.08 0.00 Max. 5.10 3.95 6.20 1.32 0.47 3.88 1.65 5.10 0.20 0.70 0.25 0.52 0.28 0.13 0.15 *: Typical, Unit: mm F 8-Lead SO-8 Plastic Surface Mounted Package AVANTICS Package Code: S Important Notice: * All rights are reserved. Reproduction in whole or in part is prohibited without the prior written approval of AVANTIC. * AVANTICS reserves the right to make changes to its products without notice. * AVANTICS semiconductor products are not warranted to be suitable for use in Life-Support Applications, or systems. * AVANTICS assumes no liability for any consequence of customer product design, infringement of patents, or application assistance. Head Office: * AVANTICS Microelectronics Corp: No. 255, Cai Lun Rd. Zhangjiang Technology Industrial Park Pudong, Shanghai, China Tel: 86-021-58955599 Fax: 86-021-58558038 AVANTICS - AX3842 Series Specification No.: 050308-FE0008 Page No. : 12/12 Soldering Methods for AVANTICS's Products 1. Storage environment: Temperature=10oC~35oC Humidity=65%15% 2. Reflow soldering of surface-mount devices Figure 1: Temperature profile tP TP Ramp-up TL Tsmax Temperature tL Critical Zone TL to TP Tsmin tS Preheat Ramp-down 25 t 25oC to Peak Time Profile Feature Average ramp-up rate (TL to TP) Preheat - Temperature Min (Tsmin) - Temperature Max (Tsmax) - Time (min to max) (ts) Tsmax to TL - Ramp-up Rate Time maintained above: - Temperature (TL) - Time (tL) Peak Temperature (TP) Time within 5oC of actual Peak Temperature (tP) Ramp-down Rate Time 25oC to Peak Temperature 3. Flow (wave) soldering (solder dipping) Products Pb devices. Pb-Free devices. Sn-Pb Eutectic Assembly <3 C/sec 100oC 150oC 60~120 sec <3oC/sec 183oC 60~150 sec 240oC +0/-5oC 10~30 sec <6oC/sec <6 minutes o Pb-Free Assembly <3oC/sec 150oC 200oC 60~180 sec <3oC/sec 217oC 60~150 sec 260oC +0/-5oC 20~40 sec <6oC/sec <8 minutes Peak temperature 245 C 5 C o o Dipping time 5sec 1sec 5sec 1sec 260 C +0/-5 C o o AVANTICS - AX3842 Series Specification No.: 050308-FE0008 |
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