LED driver enables superior performance for digital signage and displays

Diodes Incorporated has introduced a new 12-channel, constant-current LED driver, the AL58221. It features 12 open-drain outputs that are rated to 24V and sink up to 60mA of high-accuracy current with a fast transient response. The channel-to-channel LED current accuracy is typically ±1% and the regulated output current tolerance is ±0.1%.

Operating over a 3V to 5.5V input, the driver employs adaptive pulse density modulation (APDM) to help mitigate non-ideal IOUT distortion and improve visual refresh rates for enhanced performance. It can be utilised for indoor and outdoor LED video signage and displays, variable messaging signs (VMS), architectural and decorative LED lighting systems, and LCD backlighting.

The device’s LED current is set by three external resistors (for RGB master setting), with each channel’s average output current being programmed independently through its digital interface. It features a 10MHz double-edge triggered data clock input that reduces EMI. The device’s two-wire serial interface sends grayscale data to the function-control registers that store the configuration information. It controls grayscale resolution and clock frequency, current output waveform selection, and internal-latch function.

The driver uses APDM to increase the visual refresh rate of >1,000Hz at 16-bit and >256kHz at 8-bit grayscale. This technique lowers flicker and provides output-current bilateral processing for EMI reduction. The device uses a clock duty recovery technique with pulse retiming to support a longer distance connection. Its two-wire serial interface also allows cascading applications for up to 1,030 devices.

Within the same LED driver family, the recently introduced AL58263 is a 16-channel device with 16-bit PWM grayscale dimming control for higher resolution and larger display panel applications.