Small LED driver suitable for dot-matrix displays

An Austriamicrosystems product story

Edited by the Electronicstalk editorial team Aug 24, 2010

Austriamicrosystems has introduced a tiny light-emitting-diode (LED) dot-matrix driver, which is suitable for dot-matrix displays in mobile phones, personal electronics and toys.

The AS1119 drives 144 LEDs but requires only 9mm of printed circuit board (PCB) space, reduces the external component count, lowers the connector pin count and requires fewer PCB layers.

Benefits for end users include an 80 per cent longer battery lifetime, more colourful effects and smoother-running animations, according to the company.

Each LED has an 8-bit dimming control and no external resistor is required.

In addition, an 8-bit analogue current control allows the fine tuning of each matrix to compensate for the different brightness of various colours or to adjust the white balance on red-green-blue (RGB) LEDs.

The AS1119 incorporates six frames of memory for small animations or for use as a buffer to reduce host processor load, thereby saving energy and processing time.

The driver also extends battery life by including an on-chip 320mA charge pump that is required when LEDs require a higher voltage than the battery can supply, enabling continuous operation even under low battery voltage conditions.

Other features include control via a 1MHz IC-compatible interface, open and shorted LED error detection and low-power shutdown current.

Two modes of operation are offered: a single/bicolour mode to drive the maximum number of LEDs in two 8 x 9 matrix; or the RGB mode that offers three times 5 x 6 matrix, allowing white balance by adjusting the analogue current in each matrix.

Only 18 lines are required to drive all 144 LEDs.

This is accomplished with Austriamicrosystems' multiplexing technique, which is known as cross-plexing.

This allows the user to reduce the line count on the PCB as well as fewer pins on the connectors, saving space and costs.

The AS1119 is available in a 36-pin WL-CSP 3 x 3mm package and operates over a temperature range of -40C to +85C over a 2.7V to 5.5V power supply range.