5v supply


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Thread: 5v supply

  1. #1
    Join Date
    Jun 2006
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    Question 5v supply

    How can i build a high efficiency 5 volt supply for micro controllers...
    The LM7805 uses nearly 6mA for itself...
    Is there any way i can build a 5v regulator which uses less than 100uA for itself?

  2. #2
    Join Date
    Jun 2005
    Location
    Mumbai,India
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    Question Hi Efficiency?

    Quote Originally Posted by shahidali55
    How can i build a high efficiency 5 volt supply for micro controllers...
    The LM7805 uses nearly 6mA for itself...
    Is there any way i can build a 5v regulator which uses less than 100uA for itself?
    The 6mA current is not much problem but input output differential of minimum
    2.5Volts puts a big premium on efficiency. Most circuits have input of 9-10V for output of 5v. As such there is hardly 30-40% effficiency in series regulator
    like LM7805.
    For better efficiency one should use switching regulators to get 5V with
    acceptable ripple and regulation for microcontrollers. Otherway is to use
    LM2825-5V which has builtin everything and delivers 1Ampere just like 7805.
    Cost is then no consideration.

  3. #3
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    Default

    Hi,

    LP2950

    - 75 μA quiescent current
    - 100 mA output current

    http://cache.national.com/ds/LP/LP2950.pdf

    Best regards,

    Luciano


    The LP2950 and LP2951 are micropower voltage regulators
    with very low quiescent current (75 μA typ.) and very low
    dropout voltage (typ. 40 mV at light loads and 380 mV at
    100 mA). They are ideally suited for use in battery-powered
    systems. Furthermore, the quiescent current of the LP2950/
    LP2951 increases only slightly in dropout, prolonging battery
    life.


    The LP2950-5.0 is available in the surface-mount D-Pak
    package, and in the popular 3-pin TO-92 package for
    pin-compatibility with older 5V regulators. The 8-lead
    LP2951 is available in plastic, ceramic dual-in-line, or metal
    can packages and offers additional system functions.
    One such feature is an error flag output which warns of a low
    output voltage, often due to falling batteries on the input. It
    may be used for a power-on reset. A second feature is the
    logic-compatible shutdown input which enables the regulator
    to be switched on and off. Also, the part may be pin-strapped
    for a 5V, 3V, or 3.3V output (depending on the version), or
    programmed from 1.24V to 29V with an external pair of resistors.
    Careful design of the LP2950/LP2951 has minimized all contributions
    to the error budget. This includes a tight initial tolerance
    (.5% typ.), extremely good load and line regulation
    (.05% typ.) and a very low output voltage temperature coefficient,
    making the part useful as a low-power voltage reference.

    Features
    - 5V, 3V, and 3.3V versions available
    - High accuracy output voltage
    - Guaranteed 100 mA output current
    - Extremely low quiescent current
    - Low dropout voltage
    - Extremely tight load and line regulation
    - Very low temperature coefficient
    - Use as Regulator or Reference
    - Needs minimum capacitance for stability
    - Current and Thermal Limiting
    - Stable with low-ESR output capacitors


    LP2951 versions only

    - Error flag warns of output dropout
    - Logic-controlled electronic shutdown
    - Output programmable from 1.24 to 29V

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