Voltage Latch/Memory

Discussion in 'The Projects Forum' started by lattesurf, Mar 16, 2007.

  1. lattesurf

    Thread Starter New Member

    Mar 6, 2007
    As the title suggests, i'm now stuck with another problem. After solving the DC voltage averaging circuit (see post http://forum.allaboutcircuits.com/showthread.php?t=5075 ), i now need to somehow "latch" or "store" the voltage level.

    So for example, i have a DC voltage input of 5Vdc. i need a circuit or IC that can "remember"/"latch"/"store" this 5Vdc, even if the input now drops from 5Vdc to 2Vdc.
    The input ranges from 0-10Vdc, so the circuit or IC should be able to "store" any levels within the range.

    I tried the capacitor charging method, and the voltage only holds for 1-2seconds before dropping down to 2Vdc. i'm looking for a solution that would last for a longer time, maybe even a few hours. A supercapacitor might work, but again, the charge time would be very long. A maximum response time of less than 2-3seconds would be prefered.

    Currently i'm trying to limit the circuit to purely analog, i know it would be a piece of cake using a digital solution.

    Thanks for any suggestions!
  2. ashokcp

    Active Member

    Mar 8, 2007
    Maybe a low drift peak detector can work. But I am not sure whether it can hold for hours, though! I am giving a link below from National Semiconductors, which has one ckt for a low drift peak detector. Maybe, you could use ultra low leakage capacitor for holding the peak value.

    Application Note 31 Op Amp Circuit Collection - AN007057


    Hope this would be useful.
  3. nomurphy

    AAC Fanatic!

    Aug 8, 2005
    If you use an ADC it will convert your voltage into a digital value (byte) that you can store into memory -- which could theoretically last for years with the proper design.
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    You could look into a sample-and-hold circuit. If the voltage level is critical as to the level and a long hold time, then the A to D and digital storage may be the only way out.
  5. lattesurf

    Thread Starter New Member

    Mar 6, 2007
    Thanks for the suggestions, i'll look into the Low Drift Peak Detector and see if it can be incorporated into my system.
    The ADC method sounds very viable, but as mentioned i'm trying to keep my system to pure analog. Using a PIC chip was once of the solutions i've thought before. i'll try the detector circuit thing, and if it does not work, probably i'll go into the ADC method.