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Graphic LCD drivers
Introduction
Graphic Liquid Crystal Display (LCD) drivers are used to drive dot matrix type displays.
Graphic/matrix panels are capable of displaying dynamic and changeable content.
NXP's advanced, low-power graphic LCD drivers control a matrix (rows and columns) of pixels by turning them either on or off.
Using low-power CMOS LCD row/column drivers, they drive dot matrix graphic displays at multiplex rates of up to 80.
Large display matrixes not only allow more text to be displayed, but they are also used to ensure fonts are displayed sharper using finer pixels.
This is particularly important for rendering complex Asian characters or for displaying graphics, logos, or artwork.
Our PCF8811 achieves better display contrast using MRA technology.
MRA allows control of displays with four shades of grey in order to highlight or lowlight information.
This technology also enables monochrome pictures to be displayed, for example, in graphic displays with large information content.
With the exception of the PCF8578/PCF8579, all necessary functions for the display are provided in a single chip, including on-chip generation of VLCD and LCD bias voltages.
This results in a minimum of external components and lower total system power consumption.
NXP graphic LCD drivers require no external components.
The contents of the display is communicated to the LCD driver over a bus.
We have products that support communication over a Motorola parallel bus, a serial bus, an I2C bus, or an SPI bus.
This gives you the flexiblity to interface with almost any microcontroller.
Tip: Our PCF8578 graphic LCD driver (and PCF8579 expansion driver) is also ideal for driving LCD segments in larger, more complex display panels that may combine a graphics display section with additional icons.
Features
NXP Semiconductors makes graphic LCD drivers with the following available features:
On-Chip RAM
On-chip RAM stores the display data.
As a result, no refresh of the data is necessary.
This saves controller processing and bandwidth on the control bus.
On-chip RAM is a standard feature of NXP's small display drivers and often is not found in competitor products.
Power-On Reset
When first supplying power to the LCD driver, the interface and control logic are reset automatically.
All NXP LCD drivers have this feature.
The display RAM, however, is not cleared.
Clearing the display RAM should be done during initialization before enabling the display.
LCD Bias Generator
Multiplexing the display (which saves connections to the display cell) requires distinct voltage levels between VLCD and ground.
These so-called bias levels can be generated on-chip, simplifying the design.
All NXP LCD drivers (except the PCF8578 driver and PCF8579 expansion driver) have this feature.
External VLCD Supply Support
Alternatively, NXP's character LCD drivers support the use of an external VLCD supply.
By providing inputs for this voltage, our products will continue to generate the required LCD bias voltages.
This gives you component cost savings even when using an external supply.
Internal or External Clocks
In order to minimize required external components, NXP's LCD drivers include an on-chip oscillator.
In some sensitive applications, designers prefer to have control over all the frequencies and harmonics in the system.
In these cases, a specific frequency can be supplied by an external clock.
For most applications, however, the internal clock is best to use.
Products
Comparison Table
Display quality slightly degrades with higher multiplex rates.
The display height (in number of pixels) determines the multiplex rate.
| Product | Multiplex Rates | Columns | Interface | VDD | VLCD | Package(s) |
| PCF8531 | 17, 26, 34 | 128 | 400kHz I2C | 1.8 - 5.5 | 4 - 9 | Gold-Bumped Die in Tray |
| PCF8535 | 17, 26, 49, 65 | 133 | 400kHz I2C | 4.5 - 5.5 | 4.5 - 16 | Gold-Bumped Die in Tray |
| PCF8811 | 16 to 80 (in steps of 8) |
128 | 400kHz I2C, SPI, Serial, Parallel |
2 - 3.3 | 3 - 9 | Gold-Bumped Die in Tray |
| PCF8578 | 8, 16, 24, 32 | 32, 24, 16, 8 | 100kHz I2C | 2.5 - 6 | 3.5 - 9 | VSO-56, TQFP-64, Bare Die in FFC |
| PCF8579 | Driven by PCF8578 | 40 Additional |
100kHz I2C | 2.5 - 6 | 3.5 - 9 | VSO-56, TQFP-64, Bare Die in FFC |
The PCF8579 LCD column expansion driver is used with the PCF8578 to expand the number of columns in increments of 40 up to a maximum of 1280.
The PCF8579 must be used with the PCF8578.
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Graphics Drivers
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