48-output LED drivers bring vibrant signage to the masses

The next time you are driving around your local town, look around and you’ll see more full-color LED signage and message boards in front of shops, restaurants and across office building walls than ever before.  With the rapidly increasing production of LED matrix display systems, advertisement signage is now available at an affordable price to shop owners.  To support this demand, we are working hard to develop technology to further optimize the LED drivers that make these displays possible.

Earlier this year, TI unveiled a family of the world's first 48-output (48-channel) LED signage display drivers. The TLC5954, TLC5955 and TLC5958 offer three levels of integration complexity for various degrees of flexibility.

So, why would you need 48 outputs?  In the LED signage market today, 16-output drivers are used in the highest volume.  At TI, an example would be TI’s TLC5920.  So a device with 48 outputs is three times "3 ´" the number of the common 16 output devices, but the additional outputs will support all three red, green and blue (RGB) LED lamps for full-color signage applications.

In a typical LED display system design, one module consists of 16 x 16 pixels (see “LED signage terminology”) and three 16-channel devices are required to drive:

• IC1: 16 x 16 of Red
• IC2: 16 x 16 of Green
• IC3: 16 x 16 of Blue

When comparing the use of three 16-output vs. one 48-output device, the obvious advantage is higher integration, resulting in reduction of the number of driver ICs on your PCB by three times.  This in turn simplifies the PCB layout.

Below is a side-by-side comparison of a common layout showing three 16-output drivers (left) and one 48-output driver (right).  In the upper-half of each diagram, there are 256 (= 16 x 16) of RGB 3-in-1 LED lamps, which is equal to 768 individual LED lamps.  The use of a 48-channel driver dramatically simplifies the design with no wires crossing.

As an example, take a look at the TI Design featuring the 48-channel TLC5958.  In this example, you have a 64 x 64 pixel matrix design (which is 16 times larger than the examples above, for a total of 12,288 LEDs) on a 4-layer board.

As you consider these 48-channel drivers for your next design, here is some information to help you select the right device for your system.  As well, watch a video "World's first 48-channel LED display driver family."

The TLC5954 LED driver is the simplest to use, integrating brightness control and providing high flexibility with software.  It does not integrate PWM generation logic, but includes a long shift-register that directly controls ON and OFF of the output stage.  To drive the TLC5954, a powerful processor (FPGA, DSP and/or ASIC) is required to send ON/OFF data into the shift-register.  The benefit of the TLC5954 is that your software code can do anything you want with a processor.  For example, you can implement a complex and sophisticated spread-spectrum PWM signal control to avoid or minimize EMI issues.

The TLC5955 LED driver is in the middle of the three devices in terms of integration and flexibility.  The device integrates market-proven ES-PWM control to allow use of a lower power processor to control the driver.

The third member of the 48-channel LED display driver family is the highly integrated TLC5958.  It integrates 48k bit RAM to support up to 32 times of time multiplexing control.  This multiplexing reduces the number of driver ICs on your PCB.  Without integrated RAM, it was very difficult to achieve a good quality video output image due to its too short time slots.  As well, the TLC5958 integrates pre-charge FETs and low gray scale enhancement, designed specifically for a high time multiplexing display system.

I hope you give these new 48-channel drivers a try in your next signage design.  Click here for information on all of TI's LED display drivers.  Let me know how it goes?