UC3842B Motorola, UC3842B Datasheet
UC3842B
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UC3842B Summary of contents
Page 1
... High Performance Current Mode Controllers The UC3842B, UC3843B series are high performance fixed frequency current mode controllers. They 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 ...
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... OSC / T – 1.0 V OSC – 1.6 I dischg 7.8 8.3 7.5 – – – T high = +70 C for UC3842B, UC3843B T high = +85 C for UC2842B, UC2843B T high = +105 C for UC3842BV, UC3843BV UC384XB, XBV Max Min Typ Max Unit 5.05 4.9 5.0 5.1 ...
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... V OL(UVLO) – 0 – – 7.8 8.4 V CC(min) 9.0 10 7.0 7.6 T high = +70 C for UC3842B, UC3843B T high = +85 C for UC2842B, UC2843B T high = +105 C for UC3842BV, UC3843BV UC384XB, XBV Max Min Typ Max Unit 2.55 2.42 2.5 2.58 V –1.0 – – 0.1 – 2.0 A – ...
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... UC3842B, 43B UC2842B, 43B UC284XB Symbol Min Typ DC (max – – DC (min) – – – 0.3 – high = +70 C for UC3842B, UC3843B T high = +85 C for UC2842B, UC2843B T high = +105 C for UC3842BV, UC3843BV 100 500 200 100 pF 10 5.0 2.0 1.0 500 k 1.0 M ...
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... 125 C –16 Ä Ä Ä Ä – Ä Ä Ä Ä – ref , REFERENCE SOURCE CURRENT (mA) MOTOROLA ANALOG IC DEVICE DATA UC3842B, 43B UC2842B, 43B 3 –1 2.5 V 2.0 V Figure 8. Current Sense Input Threshold versus Error Amp Output Voltage 1 2 4.0 V 1.0 ...
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... UC3842B, 43B UC2842B, 43B Figure 11. Reference Load Regulation 1 2.0 ms/DIV Figure 13. Output Saturation Voltage versus Load Current 0 Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Source Saturation V CC (Load to Ground Pulsed Load Ä Ä Ä Ä Ä Ä Ä ...
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... UC3842B, 43B UC2842B, 43B Pin 8–Pin 14–Pin F Function Compensation This pin is the Error Amplifier output and is made available for loop compensation Voltage This is the inverting input of the Error Amplifier normally connected to the switching power Feedback supply output through a resistor divider Current A voltage proportional to inductor current is connected to this input ...
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... reach the comparator’s 1.0 V clamp level: R f(min) Current Sense Comparator and PWM Latch The UC3842B, UC3843B 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 (Pin 1). Thus the error signal controls the peak inductor current on a cycle– ...
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... Pin numbers in parenthesis are for the D suffix SO–14 package. Capacitor C T Latch “Set” Input Output/ Compensation Current Sense Input Latch “Reset” Input Output Large R T /Small C T MOTOROLA ANALOG IC DEVICE DATA UC3842B, 43B UC2842B, 43B V CC Reference Regulator + V CC – Internal UVLO Bias + 3.6V V ref – ...
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... All high current loops should be kept as short as 10 UC3842B, 43B UC2842B, 43B possible using heavy copper runs to minimize radiated EMI. The Error Amp compensation circuitry and the converter output voltage divider should be located close to the IC and as far as possible from the power switch and other noise– ...
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... UC3842B, 43B UC2842B, 43B Figure 20. External Clock Synchronization V ref 8(14 External Osc Sync 4( Input 0.01 2( 1(1) The diode clamp is required if the Sync amplitude is large enough to cause the bottom side more than 300 mV below ground. Figure 22. Adjustable Reduction of Clamp Level 5.0V Ref ...
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... Ref + – 7(11) + – 6(10 3(5) R Comp/Latch C The addition of the RC filter will eliminate instability caused by the leading edge spike on the current waveform. 12 UC3842B, 43B UC2842B, 43B Figure 25. Current Sensing Power MOSFET 7(12) 5.0V Ref + – 7(11) + – Q1 6(10 5(8) R ...
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... The MCR101 SCR must be selected for a holding of < 0 A(min) . The simple two transistor circuit can be used in place of the SCR as shown. All resistors are 10 k. MOTOROLA ANALOG IC DEVICE DATA UC3842B, 43B UC2842B, 43B Figure 29. Isolated MOSFET Drive V CC 7(12) 5.0V Ref + – ...
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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 14 UC3842B, 43B UC2842B, 43B Figure 32. Slope Compensation 5.0V Ref + R – Bias R + – Osc + – ...
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... UC3842B, 43B UC2842B, 43B –A– NOTE 2 –T– N SEATING PLANE 0.13 (0.005 0. SEATING PLANE MOTOROLA ANALOG IC DEVICE DATA OUTLINE DIMENSIONS N SUFFIX PLASTIC PACKAGE CASE 626–05 NOTES: ISSUE K –B– SUFFIX PLASTIC PACKAGE CASE 751–06 (SO–8) ISSUE T NOTES: ...
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... UC3842B, 43B UC2842B, 43B –A– –B– –T– K SEATING PLANE 0.25 (0.010 Motorola reserves the right to make changes without further notice to any products herein. Motorola makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Motorola assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. “ ...