S3842

Semiconductor S3842 Current Mode PWM Controller Descriptions The S3842, high performance current mode controller, Provides the necessary features to off-line and DC-DC fixed frequency current control applications offering the designer a cost effective solution with minimal external components. Internally protection circuity includes built-in input and reference under-voltage lockout and current limiting with hysteresis. Also other characteristics of internal circuit provide improved line regulation, enhanced load response, trimmed oscillation for precise duty cycle control, a temperature compensated reference, high gain error amplifier, current sensing comparator and totempole output designed to source and sink high peak current from a capacitive load such as the gate of a power MOSFET. Features • Optimized for off-line control • Low start up and operating current • Pulse by pulse current limiting • Enhanced load response characteristic • Current mode operation to 500 ㎑ • Under voltage lockout with 6V hysteresis • Internally trimmed bandgap reference about 5V • Automatic feed forward compensation Ordering Information Type NO. S3842 Marking S3842 Package Code SOP-8 Outline Dimensions unit : mm PIN Connections 1. Output / Compensation 2. Voltage feedback. Input 3. Current sense Input 4. Rt/Ct 5. GND 6. Output 7. Vcc 8. Vref KSI-8006-003 1 S3842 Absolute Maximum Ratings Characteristic Supply voltage Current Sense and Vfb Input Total Power Supply and Zener Current Output Sink of Source Current Error AMP Output Sink Current Operating Ambient Temperature Storage Temperature Range Power Dissipation at Ta≤ 50°C Ta=25°C Symbol Vcc VIN ICC+ IZ Io Ieo Ta Tstg Pd Ratings 30 -0.3 to Vcc 30 1 10 0 to 70 -65 to 150 1 Unit V V mA A mA °C °C W note) All voltages are with respect to PIN5, and current are positive into the specified pin. PIN Description PIN NO 1 2 3 4 5 6 7 8 Function Compensation Voltage feedback Current sense Rt/Ct Ground Output VCC Vref Description Error amplifier output and is made available for loop compensation. Inverting input of error amplifier, normally connected to the switching power supply output through a resistor driver. A voltage proportional to inductor current is connected to this input. The PWM uses this information to terminate the output. The oscillator frequency and maximum output duty cycle are programmed by connecting resistor Rt to Vref and capacitor Ct to ground. This pin is the combined control circuitry and power ground. This output directly drives the gate of a power MOSFET. Peak current up to 1.0A are sourced and sinked 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. Block Diagram KSI-8006-003 2 S3842 Electrical Characteristics (Unless otherwise stated, these specifications apply for 0 ≤ Ta ≤ 70°C; VCC =15V(Note.4), RL =10 ㏀, CL =3.3nF) Characteristic 1. Reference Section Output Voltage Line Regulation Load Regulation Temperature Stability Output Noise Voltage Long Term Stability Output Short Circuit Symbol Vref △Vref △Vref △VT /△VT Vn S ISC fSC △f /△V △f /△T V4 Test Condition Ta=25°C, IO=1mA 12V ≤ VCC ≤ 25V 1mA ≤ IO ≤ 20mA (Note 1) 10Hz ≤ f ≤10KHz,Ta=25°C(Note Min. 4.90 -30 47 - Typ. Max. 5.00 6 6 0.2 50 5 -100 52 0.05 5 1.7 5.10 20 25 0.4 -180 57 1.0 - Unit V mV mV mV/°C uV mV mA KHz % % V 1) - Ta=125°C, 1000Hrs (Note 1) 2. Oscillator Section Initial Accuracy Voltage Stability Temperature Stability Amplitude Ta=25°C 12 ≤ Va ≤25V Tmin ≤ Ta ≤ Tmax (Note 1) VPIN4 Peak to Peak 3. Error Amp Section Input Voltage Input Bias Current Open Loop Voltage Gain Supply Voltage Rejection Output Sink Current Output Source Current VOUT High VOUT Low V2 Ib AVO1 SVR IO IO Vch Vc1 VPIN1=2.5V 2V ≤ VO ≤ 4V 12V ≤ Va ≤ 25V VPIN2=2.7V, VPIN1=1.1V VPIN2=2.3V, VPIN1=5V VPIN2=2.3V, RL=15 ㏀ to Ground VPIN2=2.7V, RL=15 ㏀ Pin8 2.42 65 60 2 -0.5 5 2.50 -0.3 90 70 6 -0.8 6 0.7 2.58 -2.0 1.1 V ㎂ ㏈ ㏈ mA mA V V 4. Current Sense Section Gain Maximum Input Signal Supply Volt Rejection Input Bias Current GV V3 SVR Ib (Note 2 & 3) VPIN 1=5V (Note 2) 12 ≤ Va ≤ 25V (Note 2) 2.8 0.9 3.0 1.0 70 -2 3.2 1.1 -10 V/V V ㏈ ㎂ 5.Output Section Output Low Level VOl ISINK=20mA ISINK=200mA ISOURCE=20mA ISOURCE=200mA Ta=25°C, Cl=1nF (Note 1) Ta=25°C, Cl=1nF (Note 1) 13.0 12.0 0.1 1.5 13.5 13.5 50 50 0.4 2.2 150 150 V V V V ns ns Output High Level Rise time Fall time VOh tr tf KSI-8006-003 3 S3842 Electrical Characteristics(continued) Characteristic Start Threshold Min. Operation Voltage After Turn-On Symbol Vth VCC(min) Test Condition VPIN7 where VPIN8 ≥ 4.9V VPIN7 where VPIN8 ≤ 1V - Min. 14.5 8.5 Typ. Max. 16.0 10.0 17.5 11.5 Unit V V 6. Under-Voltage Lockout Section 7. PWM Section Maximum Duty Cycle DCmax Ist ICC VZ 93 97 100 ns 8. Total Standby Section Start-Up Current Operating Supply Current Zener Voltage VCC = 15V before turn on 0.4 11 36 0.7 20 mA mA V VPIN2= VPIN3=0V ICC=25mA NOTE: 1.Thes parameters, although guaranteed.are not 100% tested in production 2.Parameter measured at trip piont of latch with Vpin2= 0 3.Gain defined as : A =△VPIN1/△VPIN3 ; 0 ≤ VPIN3 ≤ 0.8V 4.Adjust VCC above the start threshold before setting at 15V Information in Using IC 1. Under voltage Lockout To prevent erratic output behavior which activating V cc 7 the power switch with extraneous leakage currents, O N /O F F C O M M A N D T O R ES ET O F IC during under voltage lockout. Output(pin6) should be shunted to ground with a bleeder resister. V o n -16V V o f f -10V Icc The Vcc comparator upper and lower threshold are 16V/10V. The large hysteresis and low start up currents makes it ideally suited in off-line converter application where efficient bootstrap start-up techniques are required.