S3882

S3882 AUK | Alldatasheet

Document overview

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Technical content

Features

• Low start up current < 0.3mA
• Operating range up to 500KHz
• Cycle by cycle current limiting
• Under Voltage Lock Out with hysteresis
• Short shutdown delay time ; typical 100nsec
• High current totempole output
• Output swing limiting : 22V

Ordering Information

Type NO. Marking Package Code S3882 S3882 SOP-8 O u t l i n e D i m e n s i o n s u n i t : mm SSeemmiiccoonndduuccttoorr PIN Connections 1. Output / Compensation 2. Voltage feedback. Input 3. Current sense Input 4. Rt/Ct 5. GND 6. Output 7. Vcc 8. Vref

A b s o l u t e M a x i m u m R a t i n g s Ta=25°C Characteristic Symbol Ratings Unit Supply Voltage Vcc 28 V Output Current Io 1 A Analog Inputs Vi(ana) -0.3 to 6.3 V Error Amp. Output Sink current Isink(EA) 10 mA Power Dissipation Pd 1 W

Electrical Characteristics

(Vcc=15V , Rt=10Kohm,Ct=3.3nF, Ta=0℃to 70℃, Unless otherwise specified) Characteristic Symbol Test Co ndition Min. Typ. Max. Unit 1. Reference Section Output Voltage Vref Tj=25℃, Io=1mA 4.91 5.00 5.09 V Line Regulation Δ Vref 12V ≤ VCC ≤ 25V - 6 20 mV Load Regulation Δ Vref 1mA ≤ IO ≤ 20mA - 6 25 mV Output Short Current Isc Ta=25°C -180 -100 - mA 2. Oscillator Section Initial Accuracy f OSC Tj=25℃ 47 52 57 KHz Voltage Stability △f /△V 12V ≤ VCC ≤ 25V - 0.2 1.0 % Oscillator Voltage V OSC V pin4, peak to peak 1.4 1.7 1.8 V Discharge Current I discharge Tj=25°C, Pin4=2V 7.8 8.3 8.8 mA 3. Error Amp Section Input Voltage V 2 V PIN1=2.5V 2.42 2.50 2.58 V Input Bias Current I b - -2.0 -0.3 - ㎂ Open Loop Voltage Gain A VO1 2V ≤ VO ≤ 4V 65 90 - ㏈ Unity Gain Bandwidth GBW Tj=25°C 0.7 1 - MHz PSRR PSRR1 V CC=12V to 25V 60 70 - ㏈ Output Sink Current I SINK V PIN2=2.7V, VPIN1=1.1V 2 6 - mA Output Source Current I SOURCE V PIN2=2.3V, VPIN1=5V -0.8 -0.5 mA Output High Voltage V OH Vpin2=2.3V, R1=15 ㏀ to GN 5 6 - V Output Low Voltage V OL VPIN2=2.3V, R1=15 ㏀ to PIN8 - 0.8 1.1 V 4. Current Sense Section Gain G V - 2.85 3.0 3.15 V/V Maximum Input Signal V i(MaX) V PIN 1=5V 0.9 1.0 1.1 V PSRR PSRR2 12V ≤ VCC ≤ 25V - 70 - ㏈ Input Bias Current I bias - -10 -2 - ㎂ Delay to Output T d V PIN 3=0V to 2V - 100 200 nS

Electrical Characteristics(continued) (Vcc=15V , Rt=10Kohm, Ct=3.3nF, Ta=0℃ to 70 ℃, Unless otherwise specified) Characteristic Symbol Test Co ndition Min. Typ. Max. Unit 5. Output Section Output Low Level1 V OL1 Isink=20mA - 0.1 0.4 V Output Low Level2 V OL2 Isink=200mA - 1.5 2.0 V Output High Level1 V OH1 Isource=20mA 13.0 13.5 - V Output High Level2 V OH2 Isource=200mA 12.0 13.5 - V Rise Time t r Tj=25°C, C1=1nF - 40 100 nS Fall Time t f Tj=25°C, C1=1nF - 40 100 nS Out Volt. Swing Limit V olim Vcc=27V, C 1=1nF - 22 - V 6. Under Voltage Lockout Section Start Threshold V th - 15 16 17 V Min. Operating Voltage V tL After turn on 9 10 11 V 7.PWM Section Maximum Duty Cycle D max - 94 96 100 % Minimum Duty Cycle D min - - - 0 % 8.Total Standby Section Start-Up Current I st - - 0.2 0.4 mA Operating Supply Current I CC Vpin2=Vpin3=0V - 11 17 mA VCC Zener Voltage V Z I CC=25mA - 29 - V N O T E : A d j u s t V c c a b o ve the the start threshold before setting at 15V Block Diagram R S - 1/3 Internal Bias Vref Set/ Reset LOGIC Oscillator 29V 22V 1/2 V ref Error Amp UV LO C. S Comp PWM LATCH Vref Vcc Vfb Com C.S Rt/Ct GND PWR Vc Output PWR GND

To prevent erratic output behavior which activating the power switch with extraneous leakage currents, during under voltage lockout. Output(pin6) should be shunted to ground with a bleeder resister. 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. The oscillator frequency is programmed by the values selected for the timing components Rt and Ct. Ct is c h a r g e d f r o m 5 V , V r e f , t h r o u g h r e s i s t o r R t t o a p p r o x i m a t e l y 2 . 8 V a n d d i s c h a r g e d t o 1 . 2 V b y a n i n t e r n a l c u r r e n t s i n k . During the discharge of Ct, the oscillator generates an internal blanking pulse and the center input NOR gate high. T h i s m a k e s o u t p u t t o b e i n a l o w s t a t e a n d c o n t r o l t h e amount of output dead time. Error amp output(Pin1) is provided for external loop c o m p e n s a t i o n a n d e r r o r a m p c a n s o u r c e o r s i n k u p t o 0 . 5 m A . The non-inverting input is internally biased at 2.5V and is not pinned out. The converter output voltage is typically d i v i d e d d o w n a n d m o n i t o r e d b y t h e i n v e r t i n g i n p u t ( p i n 2 ) . S3882 Information in Using IC 1. Under voltage Lockout 2. Oscillator Waveforms and Maximum Duty Cycle 3. Error AMP Configuration 0.5mA 1Zf Zt 2.50V Vin COMP ON/ OFF COMMAND TO RESET OF IC Vcc V on-16V V off-10V Vcc Icc <17mA <1mA 10V 16V Rt Ct LARGE Rt SMALL Ct SMALL Rt LARGE Ct Vpin4 INTERNAL CLOCK INTERNAL CLOCK Vpin4

A normal operating conditions occurs when the power supply ou tput is overloaded or if output voltage to 1.0V Therefore the maximum peak switch current is lpk(max)=1.0V/Rs, and unde r the normal operating conditions the peak inductor current controlled by the voltage at pin1. Shutdown of the S3882 can be accomplished by two methods; either raise pin3 above 1V or pull p i n 1 b e l o w a v o l t a g e t w o d i o d e s drops above ground. Either causes the output of the PWM method c o m p a r a t o r t o b e h i g h ( r e f e r t o block diagram). The PWM latch is reset dominant so that the output will remain low until the next clock cycle after the shutdown condition at pins 1 and/or 3 is removed. In one example, an externally latched shutdown may be accomplished by adding an SCR which turn off, allowing the SCR to reset. Ipeak = R(V pin1 - 2V be) 3R x Rs COMP ERROR AMP CURRENT SENSE COMPARATOR GND CURRENT SENSE Rs R C R IV Iβ S3882 4. Current Sense Circuit 5. Shutdown Techniques V REF ISENSE TO CURRENT SENSE RESISTOR SHUT DOWN 4.7K 4.7K 5.00

1 COMP

High peak currents associated with cap acitive leads necessitate careful groun ding techniques. Timing and bypass capacitors should be connected close to Pin5 in a single point ground. The transistor and 5 ㏀ potentiometer are used to sample the oscillator waveform and apply an adjustable ramp to Pin 3. A fraction of the oscillator ramp can be resistively s u m m e d w i t h t h e c u r r e n t s e n s e s i g n a l t o p r o v i d e s l o p e c o m p e n s a t i o n f o r c o n v e r t e r s r e q u i r i n g d u t y c y c l e o v e r 5 0 % . N o t e t h a t c a p a c i t o r C , f o r m s a filter with R 2 to suppress the leading edge switch s p i k e s . S3882 6. Open Loop Test 7.Slope Compensation 3ISENSE RT /CT V REF ISENSE RT CT C 0. 1uF RSENSE I ISENSE ADJUST S3882 V REF GND V REF SENSE47 K COMP Vcc OUTPUT ERROR AMP ADJUST 2N2222 RT 47 K 1K 0.1uF 0.1uF 1K/1W RT/CT Vin Vcc OUTPUT 100K

Electrical Characteristic Curves S3882 %DT PERCENT OUTPUT DEAD-TIME OUTPUT DEAD-TIME vs. OSCILLATOR FREQUENCY fOSC OSCILLATOR FREQUENCY (KHz) 1.0 2.0 5.0 100 10K 20K 50K 100K 200K 500K 1.0M Vcc=15V Ta = 25 oC Ct=10nF 2.0nF 5.0nF 1.0nF 500pF 200pF 100pF RT TIMING RESISTOR (KΩ) TIMING RESISTOR vs. OSCILLATOR FREQUENCY fOSC OSCILLATOR FREQUENCY (KHz) 0.8 2.0 5.0 8.0 10K 20K 50K 100K 200K 500K 1.0M Vcc=15V Ta = 25 oC CT=10nF 2.0nF 5.0nF 1.0nF 500pF 200pF 100pF 10 100 1K 10K 100K 1M 10M FREQUENCY (Hz) VOLTAGE GAIN (dB) Error Amplifier Open-Loop Frequency Response PHASE (o) -135 -90 -45 -180 AV φ SATURATION VOLTAGE (V) Output Saturation Characteristics OUTPUT CURRENT SOURCE OR SINK (A) Vcc=15V Ta = 25 oC Ta=-55oC SINK SAT(VOL) SOURCE SAT(Vcc-VOH)

These AUK products are intended for usage in general electronic equipments(Office and communication equipment, measuring equipment, domestic electrification, etc.). Please make sure that you consult with us before you use these AUK products in equipm- ents which require high quality and/or reliabi lity, and in equipments which could have major impact to the welfare of human life(atomic energy control, airplane, spaceship, traffic signal, combustion central, all types of safety device, etc.). AUK cannot accept liability to any damage which may occur in case these AUK products were used in the mentioned equipments without prior consultation with AUK.