Re: 1.5V devices.
- From: "GTR" <nospam@xxxxxxxxx>
- Date: Sat, 29 Oct 2005 05:50:12 GMT
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.
<jwelser@xxxxxxxxxxxxxxxxxx> wrote in message
news:djtrt7$om9$1@xxxxxxxxxxxxxxxxxxxxxxxx
> GTR <nospam@xxxxxxxxx> wrote:
> : 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
>
>
.
- References:
- 1.5V devices.
- From: GTR
- 1.5V devices.
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