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National Semiconductor LM1085 Series Specification Sheet

Manual is about: 3A Low Dropout Positive Regulators

Summary of LM1085 Series

  • Page 1

    Lm1085 3a low dropout positive regulators general description the lm1085 is a series of low dropout positive voltage regulators with a maximum dropout of 1.5v at 3a of load current. It has the same pin-out as national semiconductor’s industry standard lm317. The lm1085 is available in an adjustable ...

  • Page 2

    Ordering information package temperature range part number transport media nsc drawing 3-lead to-263 −40˚c to +125˚c lm1085is-adj rails ts3b lm1085isx-adj tape and reel lm1085is-12 rails lm1085isx-12 tape and reel lm1085is-3.3 rails lm1085isx-3.3 tape and reel lm1085is-5.0 rails lm1085isx-5.0 tape a...

  • Page 3

    Absolute maximum ratings (note 1) if military/aerospace specified devices are required, please contact the national semiconductor sales office/ distributors for availability and specifications. Maximum input to output voltage differential lm1085-adj 29v lm1085-12 18v lm1085-3.3 27v lm1085-5.0 25v po...

  • Page 4

    Electrical characteristics (continued) typicals and limits appearing in normal type apply for t j = 25˚c. Limits appearing in boldface type apply over the entire junc- tion temperature range for operation. Symbol parameter conditions min (note 6) typ (note 5) max (note 6) units i limit current limit...

  • Page 5

    Typical performance characteristics dropout voltage vs. Output current short-circuit current vs. Input/output difference 10094763 10094768 percent change in output voltage vs. Temperature adjust pin current vs. Temperature 10094799 10094798 maximum power dissipation vs. Temperature ripple rejection ...

  • Page 6

    Typical performance characteristics (continued) ripple rejection vs. Output current (lm1085-adj.) line transient response 10094744 10094772 load transient response 10094771 lm1085 www.National.Com 6.

  • Page 7

    Application note general figure 1 shows a basic functional diagram for the lm1085- adj (excluding protection circuitry) . The topology is basically that of the lm317 except for the pass transistor. Instead of a darlingtion npn with its two diode voltage drop, the lm1085 uses a single npn. This resul...

  • Page 8

    Application note (continued) figure 3 shows a typical application using a fixed output regulator. Rt1 and rt2 are the line resistances. V load is less than the v out by the sum of the voltage drops along the line resistances. In this case, the load regulation seen at the r load would be degraded fro...

  • Page 9

    Application note (continued) must be added, one for case to heat-sink ( θ ch ) and one for heatsink to ambient ( θ ha ). The junction temperature can be predicted as follows: t j = t a + p d ( θ jc + θ ch + θ ha ) = t a + p d θ ja t j is junction temperature, t a is ambient temperature, and p d is t...

  • Page 10

    Typical applications 10094767 5v to 3.3v, 1.5a regulator 10094750 adjustable @ 5v 10094752 1.2v to 15v adjustable regulator 10094753 5v regulator with shutdown 10094754 battery charger 10094755 adjustable fixed regulator 10094756 regulator with reference 10094757 high current lamp driver protection ...

  • Page 11

    Typical applications (continued) 10094759 battery backup regulated supply 10094760 ripple rejection enhancement 10094761 automatic light control 10094762 generating negative supply voltage 10094758 remote sensing lm1085 www.National.Com 11.

  • Page 12

    Physical dimensions inches (millimeters) unless otherwise noted 3-lead to-263 ns package number ts3b 3-lead to-220 ns package number t03b lm1085 www.National.Com 12.

  • Page 13: Lm1085

    Notes national does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and national reserves the right at any time without notice to change said circuitry and specifications. For the most current product information visit us at www.National.Com. ...