Low-power chipset enhances mobile colour displays

Driving the rapidly growing colour display market for mobile phones, a new chipset combines low power and advanced interface design for better colour, contrast and battery life.

Driving the rapidly growing colour display market for mobile phones, National Semiconductor has developed a chipset that uniquely combines low power and advanced interface design for better colour, contrast and battery life.

This new solution from the market leader in displays and interface technologies offers features that enable customers to differentiate products easily and cost effectively and supports all standard industry requirements.

Available for sampling late next month, this chipset will enable lighter and thinner cellphones that have longer battery life and versatile video features such as an adjustable display quality switch to save energy.

National's new chipset comprises two integrated circuits: the FPD94128 controller/column driver and the FPD93140 power supply/gate driver.

Together they form a complete solution for driving amorphous silicon active matrix LCD (AMLCD) panels used in mobile phones that support full colour graphics, video and still images.

"National Semiconductor's knowledge of complete cellular handset architectures allows us to take a more system-level perspective when designing display and imaging solutions", said Robert Fischer, Product Marketing Manager for National's portable power group in Europe.

"This new chipset is poised to be the solution of choice for mobile phone manufacturers as consumers demand no-compromise display quality for data and image-centric handsets".

The chipset features an image-dependant backlight controller for the reduction of backlight intensity, which translates to longer phone usage time between charges.

Typical backlight power of 150mW swamps the power used by the display.

Detection of high contrast images can automatically cut the display lighting power by a programmable amount, potentially reducing the lighting power by 50% or more.

External ambient light sensors can also reduce display lighting power and enhance appearance through programmable brightness controls within the chip.

The FPD94128 features programmable colour depth that allows selection of 3, 9, 12 or 18bit colour modes, which allows users to trade-off power consumption for display quality.

For example, when users are running low on battery power or want to extend usage time, they can switch then from phone display from the full 18bit (262K colour) mode to 12bit (4K colour) or 9bit (512 colour) mode.

This reduces chip power consumption by 40% in the 4K colour mode.

Additionally, the chipset has a versatile video interface, accepting data in 18bit RGB or 8bit or 16bit 4:2:2 YCbCr.

This allows direct connection to image sensors in camera-enabled phones using a more efficient 8bit interface when subsampled YCbCr data are available from the sensor.

For mobile phones capable of receiving video images, the built-in YCbCr -RGB convertor allows direct connection to the phone's MPEG decoder.

The FPD94128 integrates: a 528 channel column driver capable of driving 64 grey levels; an internal frame buffer (176 x 240 x 18bit); a display refresh controller; a programmable gamma reference; and a backlight intensity modulator.

Designed to work seamlessly with the FPD94128, the FPD93140 integrates a 241-channel row driver; high-efficiency charge pump power supplies; and a VCOM driver.

The power supply is designed to operate directly from the system Li-ion battery that can eliminate significant efficiency losses normally encountered with other display solutions.

The chips are programmable to support any physical display matrix up to 176 x 240, including the popular 176 x 220 and 176 x 208 sizes.

The FPD94128/FPD93140 chipset is priced at $9.99 each in 1000-unit quantities.

Both devices are offered as gold-bumped die for COG and COF applications.

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