I ended up finding the Teensy 3.1 for my application that is using Sharp's Ultra Low Power LCD Screens that require large amounts of SRAM since each pixel on the LCD screen requires 1 bit of memory. I'm using their 2.7 inch 400x240 pixel display which requires about 12000 bytes of SRAM for screen buffering.
This 2.7 inch screen only consumes 50 μW when displaying a static image. Hence power consumption is approximately only 1% of that of conventional transmissive TFT LCDs of the same size and even compared to conventional reflective displays the Memory LCD needs only a tenth of the power. .
http://www.sharpmemorylcd.com/2-7-inch-memory-lcd.html
Here is a video showing the screens and how they operate.
https://www.youtube.com/watch?v=eAoC818Mxy4
I'm using the Teensy 3.1 + Sharp LCD + Battery fuel gauge.
I want to put the Teensy 3.1 into deep sleep modes when the battery is not being used but I want to keep the Sharp LCD powered on while the Teensy 3.1 is in deep sleep so the battery status info is always being displayed and maybe have the Teensy 3.1 wake ever 24 hours to update the screen.
The plan is to have the Teensy 3 wake up via a button based interrupt and maybe a change in input our output current if that is possible.
My real question is what do you guys think is the best way to use the low power mode on the Teensy 3 while keep the Sharp Memory LCD powered up displaying static battery status info while the battery is in deep sleep mode. Do I need an external chip for refreshing the LCD while the Teensy is in deep sleep?
Below is some data on how the sharp display needs to be refreshed.
sharp also has an appnote on this display:
http://www.sharpmemorylcd.com/resources ... n_Info.pdf
on page 10:
This polarity-inversion flag enables a periodic polarity inversion
on the panel to keep a latent charge from building up within the
Liquid Crystal cells.
on page 12:
as long as the panel has power and VCOM is toggled periodically.
Sharp recommends keeping maximum time between VCOM toggles to no more
than one second, and refreshing data every two hours, to prevent stuck
pixels.
and on page 13:
In either implementation, the positive and negative inversion
intervals should be kept as equal as possible, and intervals should
not exceed one second.
my interpretation is that the data (12000 bytes) should be resent
at least every few hours, but that the display polarity needs to
be inverted at least one per second.