Use cheaper LEDs while maintaining light quality with dual-string LED controller

Warm-white LEDs tend to be more expensive than their more-efficacious versions that have a colder blue tinge.LED light manufacturers have a variety of schemes to provide the warmer white colors that consumers associate with the familiar-but-soon-to-be banned incandescent lights: Cree has its TrueWhite approach, which uses red LEDs inside the white-LED module that only turn on at full-on power. Pharox LED bulbs incorporate a few always-on red LEDs in the bulb to achieve a warmer white without the added intelligence of the TrueWhite approach. (For more on this approach see LED bulbs reveal different design approaches.)

Marvell is targeting lighting manufacturers’ desire to use lower-cost LEDs in lighting luminaires and bulbs with its new single chip dual-string dimmable 8800 LED lighting controller family. The first member of the family, the 88EM8801, is a single 4X4 millimeter chip that can independently control the current in two separate strings of LEDs, allowing lighting manufacturers to “tune” each string, enabling the use of  lower-cost, less-tightly-binned LEDs while still maintaining a uniform light and color temperature.

The chip’s architecture is a dual-channel DC/DC synchronous buck converter with integrated MOSFETs: The first string driver can provide up to 1A of drive current, and the second string up to 500mA. The chip has an on-chip OTP (one-time programmable) memory block for compensation and calibration data, and an I²C interface for OTP memory programming and communication with wireless lighting controls such as ZigBee, Wi-Fi and PLC. It uses intelligent pulse-width modulation (PWM) dimming controller circuitry and other digital controls to achieve deep dimming levels to 0.1 percent. No word yet on pricing.