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Chip with one-bit permanent memory

Discussion in 'Electronic Components' started by Wilfried Kaern, Jun 2, 2006.

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  1. I'm looking for a (logic)chip with one or few bits of permanet memory,
    e.g.the status is saved over a power down period. If possible at all it
    should operate in a voltage range up to 18V (automotive application).

    Many thanks for hints.

    - Wilfried
  2. Pooh Bear

    Pooh Bear Guest

    A battery backed up flip-flop or 2 ?

    More sensibly, use an eeprom.

  3. Rich Webb

    Rich Webb Guest

    Not a lot of information about what is interfaced to the bits. The
    simplest "memory" might be a 12 V nominal, latching relay rated for
    an automotive environment.
  4. Does it have to be solid state? Would a latching relay, or one of
    those twisting-solenoid pixels they use in big signage work?

    There are plenty of many-kilobit memories, but they'll depend on your
    interface requirements.

    How about a lithium battery-backed CMOS latch?

    If we knew more about the intended application, or the problem you are
    trying to solve, we might be able to be more helpful...
  5. You could use a microcontroller with on-board EEPROM. Or a latching
    relay. Or use CMOS logic with a small 'permanent' lithium battery or
    double-layer capacitor for backup.

    Best regards,
    Spehro Pefhany
  6. Sure, a latched relay would do the job. I just have the idea to realize this
    simple piece of electronic in solid state. And using an eeprom (with timing
    circuits) would be wasting most of it.

    To describe the function: Two seconds after starting the car, a (potential
    free) resistor has to be switched between 100 Ohm and infinite (open
    circuit), however, only every second time. The power used at the
    installation place is switched on and off with the car engine. So this is
    used to power the circuit and as the switch pulse. All this has to be in a
    very small housing, using little energy. The 100 Ohm resistor is used only
    for calibrating purposes, practically drawing no current. All this operated
    at car board power.

    - Wilfried
  7. Two seconds after turning the ignition on, activating the starter,
    releasing the starter, after reaching a certain number of RPMs, or
    something else?
    What's the bias on the resistor? Can you use an analog switch?

    Does the resistor return to 100 ohms when the car is turned off, or 2
    seconds after the car is started the next time?

    It sounds like you are trying to trick the car's computer into doing
    something, care to tell us what?
  8. Jamie

    Jamie Guest

    for simplicity
    12 volt latching relay, PM maintains last position and uses a pulse.
    go to mouser and look for latching relays.
    they have 28 of them at the moment for
    $18 each.
  9. Hal Murray

    Hal Murray Guest

    Sure, a latched relay would do the job. I just have the idea to realize this
    Some (many?) of the tiny one-chip CPUs include some EEPROM.

    It may seem crazy to use a part that's much much bigger than
    you need, but that is often the cheapest solution. I remember
    years ago when DEC was shipping ethernet Host ID ROMs in 64K byte
    chips. (I might be off by a few powers of two.) They only needed
    32 bytes, but that was the cheapest ROM chip they could get.
  10. Pooh Bear

    Pooh Bear Guest

    You don't by any chance mean the 2764 64k*bit* ROMs do you ?

  11. Hal Murray

    Hal Murray Guest

    It may seem crazy to use a part that's much much bigger than
    Sounds right. Thanks. (So I was off by 3 factors of 2.)

    Another example of a part that may be less expensive if you
    waste half of it. Consider using a whole CODEC or PC audio
    chip if you need either an A/D or a D/A.
  12. Pooh Bear

    Pooh Bear Guest

    Wavefront make individual stereo A/Ds and D/As that are actually quite good. I
    still had to 'overspecify' when I only needed one channel of A/D conversion
    though ! ;~)

  13. (Hal Murray) wrote in
    Can you name some parts? I might want to investigate that idea. My
    abilities and money usually limit me to modifying existing hardware, but
    that ides might be better for an accurate log converter than most of the
    ideas I've come up with or been told so far.
  14. Hal Murray

    Hal Murray Guest

    Another example of a part that may be less expensive if you
    Go to Digikey and poke CODEC into the search box. You will get
    hundreds of hits. You will have to wade through the data sheets
    to see if you can find anything that will work for your application.
  15. (Hal Murray) wrote in
    Thanks :) I'll have a look. I'm hoping something exists which has both ADC
    and DAC, plus a way to put a log converter program on it. I can imagine the
    finding of both ADC and DAC on one chip might be awkward, but hopefully
    not so.
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