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1.5V devices.

Discussion in 'Electronic Basics' started by GTR, Oct 28, 2005.

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  1. GTR

    GTR Guest

    I was curious, I have seen a number of devices which simply took a single
    AAA battery as a power source(Rio MP3 player, some IR remotes etc..).

    What is the technology behind these low voltage devices? I thought even HCT
    CMOS needed 2 volts or higher?

    Thanks
     
  2. Davy

    Davy Guest

    Hi,

    I think there is a 1.5v to 3.3v(or other higher voltage converter).

    Cheers,
    Davy
     
  3. GTR

    GTR Guest

    Does it work like a charge pump?
     
  4. Peter Howard

    Peter Howard Guest

    Yes, it does.
    If you visit www.maxim-ic.com you will find a multitude of application notes
    for all sorts of power supply ic's.
    Here's an example of just one using the familiar diode, capacitor, inductor
    and switch transistor seen in simple charge pump.
    www.maxim-ic.com/cookbook/powersupply/pdfs/CB133.pdf
    Except that the maxim ic makes it highly efficient.

    Maxim isn't the only company that does this sort of stuff. However, their
    site is particularly good because of all the technical info. And, if you ask
    nicely using their online form, they will send you out two FREE samples of
    any IC you want AND put you on their snail-mailing list. Good people, so try
    not to abuse the free sample service.

    PH
     
  5. GTR

    GTR Guest

    Thanks for the responses guys, I appreciate it.

    Chris
     
  6. Guest

    Guest Guest

    : I was curious, I have seen a number of devices which simply took a single
    : AAA battery as a power source(Rio MP3 player, some IR remotes etc..).

    : What is the technology behind these low voltage devices? I thought even HCT
    : CMOS needed 2 volts or higher?

    : Thanks

    GTR,

    Every CMOS technology/fab is different, therefore, it is not
    correct to generalize the characteristics of HCT (which IS CMOS-based
    logic) to all CMOS fabs. It's also likely that the different fabs of
    different manufacturers of HCT devices are different, and thus, the
    performance of even those two different brands is very different (although
    it probably wouldn't be speced differently.)

    That being said, assuming all devices operate in strong inversion,
    the only constraint that the technology places on the voltages is that,
    roughly speaking, the supply is greater than the threshold voltage of the
    devices (Vt.) Practically speaking, some additional headroom would be
    required, but let's not worry about that for now.

    Modern CMOS processes (0.18 -> 0.13 -> 0.09 microns ->) typically
    have Vt values of approximately 0.5V for "normal" devices, but they also
    have "low-vt" devices with Vt values as low as 0.2V, or even native
    devices with Vt of 0V (or even negative -- yes, for an NMOS device,
    meaning that the device is always on.) In fact, many of these devices
    can be damaged by any voltage significantly higher that 1.5V, due to their
    very thin gate oxide! All of these different "flavors" of MOSFET devices
    are useful in low-voltage CMOS design, but they have their problems.
    Lower Vt means larger leakage current, those native devices that I
    mentioned above basically can't be turned off, etc, all of which are
    additional challenges that need to be dealt with by the designer. My
    point is that modern processes give a designer lots of options that have
    made the design of very low voltage circuits practical.

    I am an IC designer with an interest in low-voltage/low-power (not
    the same thing!) IC design, and I can tell you that a previous design
    that I worked on, in a modern process, is able to run comfortably at 0.8V.

    So, 1.5V (which is usally speced down to 1.2V or less to deal with
    the inevitable droop of the power supply as the battery drains) operation
    is a piece of cake!

    Take it easy,

    Joe
     
  7. GTR

    GTR Guest

    Thanks for your response. I was just curious if you thought it was common
    for 1.5V devices, for example the Rio MP3 player, to use the MOSFET
    technology you described or rather a charge pump or similar technology?

    The root of my questioning in this matter is that my formal education is in
    Chemical engineering and Computer Science, electronics is just a hobby to
    me, and I suspect I will never have the training or practice to consider
    myself truly competent in it. Perhaps one day I will achieve the level of
    'hack', but time will tell :)

    I had always thought, when I further explored the hobby (to me) I would
    discover a series of off the shelf chips (Similar to jumping from TTL to
    CMOS) that would make the existence of these 1.5 volt devices evident, but I
    never did.
     
  8. Guest

    Guest Guest

    : Thanks for your response. I was just curious if you thought it was common
    : for 1.5V devices, for example the Rio MP3 player, to use the MOSFET
    : technology you described or rather a charge pump or similar technology?

    : The root of my questioning in this matter is that my formal education is in
    : Chemical engineering and Computer Science, electronics is just a hobby to
    : me, and I suspect I will never have the training or practice to consider
    : myself truly competent in it. Perhaps one day I will achieve the level of
    : 'hack', but time will tell :)

    : I had always thought, when I further explored the hobby (to me) I would
    : discover a series of off the shelf chips (Similar to jumping from TTL to
    : CMOS) that would make the existence of these 1.5 volt devices evident, but I
    : never did.

    Devices like Rio MP3 players are highly integrated, and may
    contain as little as a single IC on the board. Regardless, all
    contain a CPU/microcontroller (which may be integrated with other things
    like audio CODECS/amplifiers, etc, or it may not be) on which I will focus
    my attention in this post. This CPU is is almost certainly fabricated
    using a low-voltage CMOS process, rather than a charge-pump, followed by a
    "high" voltage CPU/microcontroller.

    One reason is simply efficiency, which translates to battery life.
    No charge pump converter is 100% efficient (I don't think that most are
    even close) so that doing things that way would result in a
    significantly shorter battery life.

    On the economic side of things, like I may have mentioned, CMOS
    devices in modern processes cannot tolerate higher voltages (because of
    their thinner gate oxides) so if a process with a smaller geometry is used
    (which will result in a smaller chip area = lower cost for the
    manufacturer = desirable for the manufacturer) lower supply voltages MUST
    be used.

    Therefore, for this type of application (low-voltage digital CMOS
    design) the economic and the technical aspects of the design re-inforce
    each other, making it VERY likely for that the be the prevailing method of
    design.

    Does that make sense? Things ARE more complicated than that, but
    this is a "basics" newsgroup, and those are pretty much the basics of what
    drives/helps drive modern low-voltage IC design, which has made (and
    will continue to make) lots of new low-voltage products available
    recently.

    Take it easy,

    Joe

    : :> : I was curious, I have seen a number of devices which simply took a
    : single
    :> : AAA battery as a power source(Rio MP3 player, some IR remotes etc..).
    :>
    :> : What is the technology behind these low voltage devices? I thought even
    : HCT
    :> : CMOS needed 2 volts or higher?
    :>
    :> : Thanks
    :>
    :> GTR,
    :>
    :> Every CMOS technology/fab is different, therefore, it is not
    :> correct to generalize the characteristics of HCT (which IS CMOS-based
    :> logic) to all CMOS fabs. It's also likely that the different fabs of
    :> different manufacturers of HCT devices are different, and thus, the
    :> performance of even those two different brands is very different (although
    :> it probably wouldn't be speced differently.)
    :>
    :> That being said, assuming all devices operate in strong inversion,
    :> the only constraint that the technology places on the voltages is that,
    :> roughly speaking, the supply is greater than the threshold voltage of the
    :> devices (Vt.) Practically speaking, some additional headroom would be
    :> required, but let's not worry about that for now.
    :>
    :> Modern CMOS processes (0.18 -> 0.13 -> 0.09 microns ->) typically
    :> have Vt values of approximately 0.5V for "normal" devices, but they also
    :> have "low-vt" devices with Vt values as low as 0.2V, or even native
    :> devices with Vt of 0V (or even negative -- yes, for an NMOS device,
    :> meaning that the device is always on.) In fact, many of these devices
    :> can be damaged by any voltage significantly higher that 1.5V, due to their
    :> very thin gate oxide! All of these different "flavors" of MOSFET devices
    :> are useful in low-voltage CMOS design, but they have their problems.
    :> Lower Vt means larger leakage current, those native devices that I
    :> mentioned above basically can't be turned off, etc, all of which are
    :> additional challenges that need to be dealt with by the designer. My
    :> point is that modern processes give a designer lots of options that have
    :> made the design of very low voltage circuits practical.
    :>
    :> I am an IC designer with an interest in low-voltage/low-power (not
    :> the same thing!) IC design, and I can tell you that a previous design
    :> that I worked on, in a modern process, is able to run comfortably at 0.8V.
    :>
    :> So, 1.5V (which is usally speced down to 1.2V or less to deal with
    :> the inevitable droop of the power supply as the battery drains) operation
    :> is a piece of cake!
    :>
    :> Take it easy,
    :>
    :> Joe
    :>
    :>
     
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