Low Power with High Contrast LCD Displays

If your next portable battery project involves the need for a high contrast low-power (microwatt range) LCD display and you need it now, read on. Occasionally an existing technology is improved to push components into new usage areas. Sharp has done that with the monochrome LCD display, pushing it into microwatt power consumption territory while approaching e-ink display contrast levels. Coupled with pixel memory, they are call memory LCDs.

The family of displays includes options. The polymer network liquid crystal (PNLC) high contrast design of some part numbers is almost mirror-reflective (avoiding polarization) approaching e-ink readability levels and wide viewing angles.

The HR-TFT models go the traditional route with polarization added and achieve deep black levels. Both types use very little power (were talking microwatts!) in maintaining the display and also during display updates.

A related podcast at the?Sharp website?explains the advantages of its display. Very low power consumption, small size, and high contrast lead the charge. The interface is a 3-wire SPI-type interface. A frame switching signal of low frequency is required and can be implemented via hardware or software. It is a pixel-based display that requires update data one line at a time. Sharp refers to the product as memory LCD because each pixel has on-display 1-bit memory. You can only write to the pixel memory so an image is probably required in software for screen manipulation.

Display refresh rates are not at full screen flicker-free video levels but there is no evident flicker when updating portions of the screen.

Since seeing is believing, it would be beneficial to be able to easily prototype the displays to experience the advantages first-hand. Breakout boards for the memory LCDs are available for quick prototyping from Richard at MakerDyne and Kuzyatech at his Tindie site. The includes links to various demonstration videos and software libraries.