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LM117HV Scheda tecnica(PDF) 10 Page - Texas Instruments |
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LM117HV Scheda tecnica(HTML) 10 Page - Texas Instruments |
10 / 28 page LM117HV, LM317HV SNVS773D – APRIL 2000 – REVISED SEPTEMBER 2015 www.ti.com 8.3 Feature Description 8.3.1 Load Regulation The LM317HV is capable of providing extremely good load regulation but a few precautions are needed to obtain maximum performance. The current set resistor, R1, should be connected near the output terminal of the regulator rather than near the load. If R1 is placed too far from the output terminal, then the increased trace resistance, RS, will cause an error voltage drop in the adjustment loop and degrade load regulation performance. Therefore, R1 should be placed as close as possible to the output terminal to minimize RS and maximize load regulation performance. Figure 14 shows the effect of the trace resistance, RS, when R1 is placed far from the output terminal of the regulator. It is clear that RS will cause an error voltage drop especially during higher current loads, so it is important to minimize the RS trace resistance by keeping R1 close to the regulator output terminal. Figure 14. Regulator With Line Resistance in Output Lead With the TO-3 package, it is easy to minimize the resistance from the case to the set resistor, by using two separate leads to the case. However, with the TO-39 package, take care to minimize the wire length of the output lead. The ground of R2 can be returned near the ground of the load to provide remote ground sensing and improve load regulation. 8.3.2 Current Limit Internal current limit will be activated whenever the output current exceeds the limit indicated in Typical Characteristics. However, if the regulators differential voltage exceeds the absolute maximum rating of 60 V during a short-circuit condition (for example: VIN ≥ 60 V, VOUT = 0 V), internal junctions in the regulator may break down and the device may be damaged or fail. Failure modes range from an apparent open or short from input to output of the regulator, to a destroyed package (most common with the TO-220 package). To protect the regulator, the user is advised to be aware of voltages that may be applied to the regulator during fault conditions and to avoid violating the Absolute Maximum Ratings. 8.4 Device Functional Modes 8.4.1 External Capacitors An input bypass capacitor is recommended. A 0.1- μF disc or 1-μF solid tantalum on the input is suitable input bypassing for almost all applications. The device is more sensitive to the absence of input bypassing when adjustment or output capacitors are used but the above values will eliminate the possibility of problems. The adjustment terminal can be bypassed to ground on the LM317HV to improve ripple rejection. This bypass capacitor prevents ripple from being amplified as the output voltage is increased. With a 10- μF bypass capacitor the 80-dB ripple rejection is obtainable at any output level. Increases over 10 μF do not appreciably improve the ripple rejection at frequencies above 120 Hz. If the bypass capacitor is used, it is sometimes necessary to include protection diodes to prevent the capacitor from discharging through internal low current paths and damaging the device. 10 Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated Product Folder Links: LM117HV LM317HV |
Codice articolo simile - LM117HV_16 |
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Descrizione simile - LM117HV_16 |
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