12-Channel RGB-LED Driver Enhances Lighting Effects on Wearables
With patented features to prevent distracting artifacts in "color-chasing" or "deep breathing" LED animation effects, the STMicroelectronics' new LED1202 12-channel LED driver enables smoother and more natural interactions with smart-home devices, small appliances, and wearable electronics.
Typical applications for the RGB LED driver include RGB LED lighting, fade-in and fade-out breathing effect, indicator lights for wearable electronics, battery-powered devices, and portable accessories.
The LED1202 can store eight programmable patterns and sequences and operate independently of the primary controller, allowing the host system to save power while the sophisticated lighting effects run continuously. 12-bit internal PWM dimming can precisely control programmed sequences, and the main controller can set 8-bit values for analog dimming through the driver's I2C interface. Minimal external components are needed to complete the driver circuit.
With 12 output channels, a single LED1202 can drive four RGB LEDs at up to 20mA per channel. An innovative synchronization feature allows connecting up to eight LED1202 drivers to control larger LED arrays.
Moreover, superior low-current channel matching, within 2% (typical) at 2.5mA, improves color consistency. Phase shifting between channels minimizes current ripple and prevents excessive peak demand. Built-in safety features include open-LED detection, over-temperature protection, and a fault-flag pin.
LED1202 Simplified block diagram (Click on image to enlarge)
The LED driver guarantees 5V output and each channel can provide up to 20mA with a headroom voltage of 350mV typical. The output current can be adjusted separately for each channel via 8-bit analog and 12-bit digital dimming control. A slow turn-on and turn-off times enhance a system's low noise generating performance. Furthermore, the phase shifting function helps to reduce the inrush current.
Without MCU intervention, eight patterns can be stored in the internal registers for automatic sequencing. The pattern sequence can be also configured for duration time and number of repetitions. For multi-device applications, a common clock domain can be shared for timing synchronization.
The device offers thermal shutdown and open LED detection. Its I²C interface is based on fast mode specification and works up to 400kHz. Eight I²C addresses are possible by using two configuration pins (A0/A1) only.
Available now, the LED1202JR in 1.71mm x 2.16mm WLCSP-20 flip-chip is $0.90 and the LED1202QTR in 3mm x 3mm VFQFPN-20 is $1.15 for orders of 1000 pieces.
The STEVAL-LLL007V1 evaluation kit is also available to support evaluation of the LED1202 and aids development of new products and lighting sequences.
Features
- Supply range from 2.6V to 5V
- 12 channels for single LED
- 20mA current capability per channel
- 1% (typ.) current matching at 16mA and 2% (typ.) at 2.5mA
- 1.8V compatible I²C control interface
- 8-bit analog dimming individual control
- 12-bit local PWM resolution
- 8 programmable patterns
- Programmable pattern sequence
- Synchronization for multi-device application
- Phase shifting between channels
- Open LED detection
- Over-temperature protection
- 8 configurable I²C slave addresses plus global address
- Fault flag pin
