UC3842A Motorola, UC3842A Datasheet
UC3842A
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UC3842A Summary of contents
Page 1
... High Performance Current Mode Controllers The UC3842A, UC3843A series of high performance fixed frequency current mode controllers are specifically designed for off–line and dc–to–dc converter applications offering the designer a cost effective solution with minimal external components. These integrated circuits feature a trimmed ...
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... I SC – 30 – osc – f osc/ V – 0.2 f osc/ T – 5.0 V osc – 1.6 I dischg 7.5 8.4 7.2 – T high = +70 C for UC3842A, UC3843A T high = +85 C for UC2842A, UC2843A UC384XA Max Min Typ Max Unit 5.05 4.9 5.0 5 – 2 – 3.0 ...
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... Power Supply Zener Voltage ( mA) NOTES: 2. Adjust V CC above the Startup threshold before setting Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible T low = –20 C for UC3842A, UC3843A T low = –25 C for UC2842A, UC2843A 4. This parameter is measured at the latch trip point with ...
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... AMBIENT TEMPERATURE ( C) Figure 5. Error Amp Small Signal Transient Response 2.55 V 2.5 V 2.45 V 0.5 s/DIV 4 UC3842A, 43A UC2842A, 43A Figure 2. Output Deadtime versus 100 5.0 2.0 1.0 500 k 1 Figure 4. Maximum Output Duty Cycle 100 ...
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... UC3842A, 43A UC2842A, 43A Figure 7. Error Amp Open Loop Gain and Phase versus Frequency 100 2 4 100 K Gain – 100 1 100 k f, FREQUENCY (Hz) Figure 9. Reference Voltage Change versus Source Current 0 –4.0 –8.0 –12 – 125 – – ref , REFERENCE SOURCE CURRENT (mA) Figure 11 ...
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... UC3842A, 43A UC2842A, 43A Figure 13. Output Saturation Voltage versus Load Current 0 Source Saturation V CC (Load to Ground) –1 –2 – –55 C 2.0 1.0 Sink Saturation (Load 200 400 OUTPUT LOAD CURRENT (mA) Figure 15. Output Cross Conduction 100 ns/DIV 6 Figure 14. Output Waveform Pulsed Load ...
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... UC3842A, 43A UC2842A, 43A Figure 17. Representative Block Diagram V ref 8(14) R Internal Bias 2. Oscillator 4( 1.0mA + – Voltage Feedback Input 2(3) Error Output Amplifier Compensation 1(1) Pin numbers in parenthesis are for the D suffix SO–14 package. Capacitor C T Latch ‘‘Set’’ Input ...
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... reach the comparator’s 1.0 V clamp level: R f(min) Current Sense Comparator and PWM Latch The UC3842A, UC3843A operate as a current mode controller, whereby output switch conduction is initiated by the oscillator and terminated when the peak inductor current reaches the threshold level established by the Error Amplifier Output/Compensation (Pin1). Thus the error signal controls the peak inductor current on a cycle– ...
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... These devices contain a single totem pole output stage that was specifically designed for direct drive of power MOSFETs capable 1.0 A peak drive current and MOTOROLA ANALOG IC DEVICE DATA UC3842A, 43A UC2842A, 43A PIN FUNCTION DESCRIPTION D Description This pin is Error Amplifier output and is made available for loop compensation. ...
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... m2/m1. The minimum current at the next cycle ( decreases This pertubation is multiplied UC3842A, 43A UC2842A, 43A DESIGN CONSIDERATIONS each succeeding cycle, alternately increasing and decreasing the inductor current at switch turn–on. Several oscillator cycles may be required before the inductor current reaches zero causing the process to commence again ...
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... V Clamp S 1.0mA + – – 2(3) Comp/Latch R R2 1.0V 1(1) 5(9) MPSA63 C R1 1.67 V Clamp = I pk(max) = VClamp Softstart = – In MOTOROLA ANALOG IC DEVICE DATA UC3842A, 43A UC2842A, 43A Figure 21. External Duty Cycle Clamp and Multi Unit Synchronization 5. – – 5.0k C MC1455 1 5(9) 1. max = ( ...
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... UC3842A, 43A UC2842A, 43A Figure 26. Current Waveform Spike Suppression V CC 7(12) + 5.0V ref – + – + – + 7(11) – 6(10 – 5( Comp/Latch 3(5) The addition of the RC filter will eliminate instability caused by the leading edge spike on the current waveform. Figure 28. Bipolar Transistor Drive ...
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... 115 Vac, I out = 1 4 115 Vac, I out = 100 mA to 300 mA Output Ripple: 5 115 Vac 12 V Efficiency 115 Vac All outputs are at nominal load currents, unless otherwise noted. MOTOROLA ANALOG IC DEVICE DATA UC3842A, 43A UC2842A, 43A Figure 32. Slope Compensation 7(12) + 5.0V ref – Bias – + – ...
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... USA / EUROPE / Locations Not Listed: Motorola Literature Distribution; P.O. Box 20912; Phoenix, Arizona 85036. 1–800–441–2447 or 602–303–5454 MFAX: RMFAX0@email.sps.mot.com – TOUCHTONE 602–244–6609 INTERNET: http://Design–NET.com 14 UC3842A, 43A UC2842A, 43A OUTLINE DIMENSIONS N SUFFIX PLASTIC PACKAGE CASE 626–05 ISSUE K – ...