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UC1842 Datasheet(PDF) 21 Page - Texas Instruments |
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UC1842 Datasheet(HTML) 21 Page - Texas Instruments |
21 / 56 page COMP VFB UCx842 ISENSE RT/CT 1 2 3 4 VREF VCC OUTPUT GROUND 8 7 6 5 0.1 PF R1 CRTCT 100 NŸ 5 NŸ ISENSE Adjust 1 NŸ E/A Adjust 4.7 NŸ 4.7 NŸ 0.1 PF GROUND 1 NŸ OUTPUT VREF VCC Copyright © 2016, Texas Instruments Incorporated 21 UC1842, UC2842, UC3842, UC1843, UC2843, UC3843 UC1844, UC2844, UC3844, UC1845, UC2845, UC3845 www.ti.com SLUS223D – APRIL 1997 – REVISED AUGUST 2016 Product Folder Links: UC1842 UC2842 UC3842 UC1843 UC2843 UC3843 UC1844 UC2844 UC3844 UC1845 UC2845 UC3845 Submit Documentation Feedback Copyright © 1997–2016, Texas Instruments Incorporated 9 Application and Implementation NOTE Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality. 9.1 Application Information The UCx84x controllers are peak current mode pulse width modulators. These controllers have an onboard amplifier and can be used in isolated and non-isolated power supply design. There is an onboard totem pole gate driver capable of delivering 1 A of peak current. This is a high-speed PWM capable of operating at switching frequencies up to 500 kHz. 9.1.1 Open-Loop Test Fixture The following application is an open-loop laboratory test fixture. This circuit demonstrates the setup and use of the UCx84x devices and their internal circuitry. In the open-loop laboratory test fixture (see Figure 24), high peak currents associated with loads necessitate careful grounding techniques. Timing and bypass capacitors should be connected close to the GROUND terminal in a single-point ground. The transistor and 5-kΩ potentiometer sample the oscillator waveform and apply an adjustable ramp to the ISENSE terminal. Figure 24. Open-Loop Laboratory Test Fixture 9.2 Typical Application A typical application for the UC2842 in an off-line flyback converter is shown in Figure 25. The UC2842 uses an inner current control loop that contains a small current sense resistor which senses the primary inductor current ramp. This current sense resistor transforms the inductor current waveform to a voltage signal that is input directly into the primary side PWM comparator. This inner loop determines the response to input voltage changes. An outer voltage control loop involves comparing a portion of the output voltage to a reference voltage |
Similar Part No. - UC1842_16 |
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Similar Description - UC1842_16 |
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