LED Driver ICs with Built-in Display Pattern Data Optimized for Illumination
Control in Portables

Semiconductor manufacturer ROHM Co., Ltd. has announced the development of an LED driver IC series optimized for portable devices of all types, including mobile phones and car audio equipment. Features include built-in display pattern data and automatic illumination control that lightens CPU load. Two models are offered: the BD2802GU (2.8×2.8×1.0mm) designed to drive 6 LEDs, and the BD2812GU (3.1×3.1×1.0mm) which integrates a boost circuit.

The continuing trend towards greater sophistication in electronic devices has been accompanied by an equally large need for high performance LED illumination. Conventional LED driver ICs normally do not include an illumination control function, making fine current control difficult. Additional problems that often arise are flickering and/or inflexible design. And while LED driver ICs equipped with an illumination function do exist, the variety is often insufficient and the degree of sophistication severely limited. Problems such as the necessity of noise countermeasures when performing highly expressive and complicated LED illumination and the increased load on the CPU required when performing illumination control occur.

In order to meet these demands, ROHM has developed the BD2802GU and BD2812GU driver ICs for driving 6 LED lamps (two RBG LEDs). The units are offered in an ultra-compact WL-CSP (Wafer Level Chip Scale Package) featuring a pitch of 0.5mm for easy mounting in mobile devices. Both types feature 7-bit gradation (128 steps) and integrate a constant current DAC for lower EMI noise and reduced flickering. Integrated display pattern data enables automatic illumination control, eliminating CPU load. The display patterns of each of the 6 LEDs can be set individually, and 7-bit (128-step) resolution results in up to 2,097,000 colors (R:128 steps × G:128 steps × B:128 steps) for smooth, highly expressive LED illumination. By changing the device control address both the BD2802GU and BD2812GU can be configured to drive greater number of lamps for larger scale applications.

Main features of the BD2802GU and BD2812GU

1. Drives up to 6 lamps (30.48mA max.)
2. Constant current circuit with dimming function plus 7-bit gradation (128 steps) for all 6 lamps
3. I²C address change and reference clock input/output functions enable simultaneous operation of multiple units
4. Built-in charge pump circuit (BD2812GU only)
5. Control interface: Supports fast mode (400kHz max.) I²C-bus format
6. Compact WL-CSP (Wafer Level Chip Scale Package) ideal for portable devices
      •Constant current type (BD2802GU): VCSP85H2 package (2.8×2.8×1.0mm, 0.5mm pitch)
      •Built-in boost circuit type (BD2812GU): VCSP85H3 package (3.1×3.1×1.0mm, 0.5mm pitch)

RGB LED Driver ICs for Illumination BD2802GU/ BD2812GU (PDF:324KB)

Glossary

• LED illumination drive types
  While ON/OFF control is common for discrete devices, illumination lighting processing is controlled by the CPU, making control more complex. Fluctuations in the forward voltage (Vf) of an LED causes differences in LED color, affecting the color tone during RGB LED display. In addition, conventional LED driver ICs used in many lighting products are not capable of fine current control via CPU, making smooth dimming difficult or even impossible to achieve.
• Automatic illumination function with built-in display patterns
  In LED illumination lighting devices it is necessary to change (in steps) the current flowing through the LEDs. Repeated operation requires patterns for changing the LED current.
• 16 types of basic waveform patterns are built-in, comprised of ON/OFF combinations. Selecting from among these 16 patterns, setting the ON/OFF current slope as well as the maximum and minimum current values, and configuring the default setting (i.e. single shot or Reference clock input function Time management is required when generating illumination patterns. Sharing reference clocks (the basic unit of time) across multiple chips make it possible to perform synchronous illumination patterns.
• Charge pump circuit
  An electronic circuit that steps up voltage by combining a capacitor and a switch. Used in power source circuits in which the output voltage is higher than the input voltage. In this case it is used to drive the LEDs.

	Illumination LED Driver with Built-in Display Patterns