UC3842B STMicroelectronics, UC3842B Datasheet
UC3842B
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UC3842B Summary of contents
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... The UC3842B and UC3844B have UVLO thresholds of 16V (on) and 10V (off), ideally suitedoff-lineapplicationsThecorrespondingthresh- oldsforthe UC3843BandUC3845Bare8.5 V and7.9 V. The UC3842B and UC3843B can operate to duty cycles approaching 100%. A range of the zero to < obtained by the UC3844B and UC3845B by the addition of an internal toggle flip flopwhich blanks the output off every otherclock cycle ...
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... UC2842B/3B/4B/5B - UC3842B/3B/4B/5B ABSOLUTE MAXIMUM RATINGS Symbol V Supply Voltage (low impedance source Supply Voltage (Ii < 30mA Output Current O E Output Energy (capacitive load) O Analog Inputs (pins 2, 3) Error Amplifier Output Sink Current P Power Dissipation at T tot amb P Power Dissipation at Tamb ...
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... OUT CURRENT SENSE SECTION G Gain V V Maximum Input Signal 3 SVR Supply Voltage Rejection I Input Bias Current b Delay to Output UC2842B/3B/4B/5B - UC3842B/3B/4B/5B Minid ip max. 100 < for UC384XB 15V (note 5); R amb i UC284XB T est Cond it ion s Min. Typ. Max. Min. Typ. Max. 4.95 5.00 5.05 4.90 5.00 5. ...
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... UC2842B/3B/4B/5B - UC3842B/3B/4B/5B ELECTRICAL CHARACTERISTICS (continued) Symbo l Parameter OUTPUT SECTION V Output Low Level OL V Output High Level OH V UVLO Saturation OLS t Rise Time r t Fall Time f UNDER-VOLTAGE LOCKOUT SECTION Start Threshold Min Operating Voltage After Turn-on PWM SECTION Maximum Duty Cycle Minimum Duty Cycle ...
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... =5nF =2nF T C =10nF =15V 0.8 10K 20K 30K 50K 100K 200K 300K UC2842B/3B/4B/5B - UC3842B/3B/4B/ REF 0.1 F COMP 0.1 F UC2842B I SENSE 3 OUTPUT GROUND pin single point ground. The transistor and 5 K potentiometerareusedto samplethe oscillator waveform and apply an adjustable ramp to pin 3 ...
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... UC2842B/3B/4B/5B - UC3842B/3B/4B/5B Figure 4: Oscillator Discharge Current vs. Tem- perature. I dischg (mA) V =15V i V =2V OSC 8.5 8.0 7.5 7.0 -55 - Figure 6: Error Amp Open-Loop Gain and Phase vs. Frequency. (dB) V =15V =100K L Gain T = -20 10 100 1K 10K 100K 1M Figure 8: Reference Voltage Change vs. ...
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... Figure 12: Output Waveform. 90% 10% 50ns/DIV Figure 14: Oscillator and Output Waveforms REG PWM R T CLOCK 4 OSCILLATOR UC2842B/3B/4B/5B - UC3842B/3B/4B/5B Figure 11: Supply Current vs. Supply Voltage D95IN341 (mA GND (mA) O Figure 13: Output Cross Conduction V =15V ...
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... UC2842B/3B/4B/5B - UC3842B/3B/4B/5B Figure 15 : Error Amp Configuration Figure 16 : Under Voltage Lockout. 7 ON/OFF COMMAND V TO REST UC3842B UC3844B V 16V ON V 10V OFF Figure 17 : Current Sense Circuit . I S COMP R CURRENT SENSE GND D95IN347 Peak current ( determined by the formula s 1 max ...
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... UC3842B R C SLOPE SENSE Figure 19 : Isolated MOSFET Drive and Current Transformer Sensing 5.0V ref - + - COMP/LATCH D95IN349 UC2842B/3B/4B/5B - UC3842B/3B/4B/ SLOPE GND V ISOLATION BOUNDARY REG UC3842B ...
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... UC2842B/3B/4B/5B - UC3842B/3B/4B/5B Figure 20 : Latched Shutdown. 2N 3905 SCR must be selected for a holding current of less than 0.5mA at T The simple two transistor circuit can be used in place of the SCR as shown. All resistors are 10K. Figure 21: Error Amplifier Compensation From Error Amp compensation circuit for stabilizing any current-mode topology except for boost and flyback converters operating with continuous inductor current ...
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... Figure 23: External Duty Cycle Clamp and Multi Unit Synchronization. V REF NE555 1 1. max ( UC2842B/3B/4B/5B - UC3842B/3B/4B/5B V REF BIAS OSC D95IN352 R BIAS R OSC + 2R + ...
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... UC2842B/3B/4B/5B - UC3842B/3B/4B/5B Figure 24: Soft-Start Circuit Figure 25: Soft-Start and Error Amplifier Output Duty Cycle Clamp 1mA + BC109 · CLAMP 12/15 5V ref R BIAS R OSC + 1mA ref + BIAS - OSC V S Clamp Comp/Latch ...
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... F (1) 3.8 4.0 0.15 L 0.4 1.27 0.016 M 0 (max.) (1) D and F do not include mold flash or protrusions. Mold flash or potrusions shall not exceed 0.15mm (.006inch). UC2842B/3B/4B/5B - UC3842B/3B/4B/5B inch OUTLINE AND TYP. MAX. MECHANICAL DATA 0.069 0.010 0.065 0.033 0.019 0.010 0.020 0.197 0.244 0.050 0.150 ...
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... UC2842B/3B/4B/5B - UC3842B/3B/4B/5B mm DIM. MIN. TYP. MAX. MIN. A 3.32 a1 0.51 0.020 B 1.15 1.65 0.045 b 0.356 0.55 0.014 b1 0.204 0.304 0.008 D 10.92 E 7.95 9.75 0.313 e 2.54 e3 7.62 e4 7.62 F 6.6 I 5.08 L 3.18 3.81 0.125 Z 1.52 14/15 inch OUTLINE AND MECHANICAL DATA TYP. MAX. 0.131 0.065 0.022 0.012 0.430 0.384 0.100 0.300 0.300 0.260 0.200 0.150 0.060 ...
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... The ST logo is a registered trademark of STMicroelectronics 1999 STMicroelectronics – Printed in Italy – All Rights Reserved STMicroelectronics GROUP OF COMPANIES Australia - Brazil - Canada - China - France - Germany - Italy - Japan - Korea - Malaysia - Malta - Mexico - Morocco - The Netherlands - Singapore - Spain - Sweden - Switzerland - Taiwan - Thailand - United Kingdom - U.S.A. UC2842B/3B/4B/5B - UC3842B/3B/4B/5B http://www.st.com 15/15 ...