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LM2936MP-5.0 Fiches technique(PDF) 5 Page - National Semiconductor (TI) |
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LM2936MP-5.0 Fiches technique(HTML) 5 Page - National Semiconductor (TI) |
5 / 9 page Typical Performance Characteristics (Continued) Applications Information Unlike other PNP low dropout regulators, the LM2936 re- mains fully operational to 40V. Owing to power dissipation characteristics of the available packages, full output current cannot be guaranteed for all combinations of ambient tem- perature and input voltage. As an example, consider an LM2936Z operating at 25˚C ambient. Using the formula for maximum allowable power dissipation given in (Note 3) , we find that P Dmax = 641 mW at 25˚C. Including the small con- tribution of the quiescent current to total power dissipation the maximum input voltage (while still delivering 50 mA out- put current) is 17.3V. The LM2936Z will go into thermal shut- down if it attempts to deliver full output current with an input voltage of more than 17.3V. Similarly, at 40V input and 25˚C ambient the LM2936Z can deliver 18 mA maximum. Under conditions of higher ambient temperatures, the volt- age and current calculated in the previous examples will drop. For instance, at the maximum ambient of 125˚C the LM2936Z can only dissipate 128 mW, limiting the input volt- age to 7.34V for a 50 mA load, or 3.5 mA output current for a 40V input. The junction to ambient thermal resistance θ JA rating has two distinct components: the junction to case thermal resis- tance rating θ JC; and the case to ambient thermal resistance rating θ CA. The relationship is defined as: θJA = θJC + θCA. For the SO-8 and TO-252 surface mount packages the θ JA rating can be improved by using the copper mounting pads on the printed circuit board as a thermal conductive path to extract heat from the package. On the SO-8 package the four ground pins are thermally connected to the backside of the die. Adding approximately 0.04 square inches of 2 oz. copper pad area to these four pins will improve the θ JA rating to approximately 110˚C/W. If this extra pad are is placed directly beneath the package there should not be any impact on board density. On the TO-252 package the ground tab is thermally con- nected to the backside of the die. Adding 1 square inch of 2 oz. copper pad area directly under the ground tab will im- prove the θ JA rating to approximately 50˚C/W. While the LM2936 has an internally set thermal shutdown point of typically 150˚C, this is intended as a safety feature only. Continuous operation near the thermal shutdown tem- perature should be avoided as it may have a negative affect on the life of the device. While the LM2936 maintains regulation to 60V, it will not withstand a short circuit above 40V because of safe operat- ing area limitations in the internal PNP pass device. Above 60V the LM2936 will break down with catastrophic effects on the regulator and possibly the load as well. Do not use this device in a design where the input operating voltage may ex- ceed 40V, or where transients are likely to exceed 60V. Line Transient Response DS009759-19 Output at Voltage Extremes DS009759-20 Ripple Rejection DS009759-21 Load Transient Response DS009759-22 Low Voltage Behavior DS009759-23 Output Impedance DS009759-24 www.national.com 5 |
Numéro de pièce similaire - LM2936MP-5.0 |
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Description similaire - LM2936MP-5.0 |
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