Power Electronics

TAOS light-to-digital converters simplify ambient light sensing in display panels

Texas Advanced Optoelectronic Solutions (TAOS) has introduced two light-to-digital converters to simplify the design and deployment of ambient light sensing in display panel products.

The patented, single-chip TSL2560 (SMBus interface) and TSL2561 (I2C interface) digital light sensors are designed for use in display panels to extend battery life and provide optimum viewing in diverse lighting conditions by converting light intensity to a digital signal output.

The devices enable automatic management of display panel backlighting, which can account for up to 40% of total platform power, and can also be used to help control keyboard illumination based on ambient light conditions.

They combine a visible light-blocking photodiode with a broadband photodiode on a single CMOS integrated circuit. Each device can calculate light intensity in lux over an effective 20-bit dynamic range with a 16-bit resolution without the use of an expensive filter. Two integrating analog-to-digital converters convert the photodiode currents to either an SMBus or an I²C digital output that represents the irradiance measured on each channel. The output data can be input to a microprocessor where illuminance (ambient light level) in lux is derived using an empirical formula that requires less than 200 bytes of code.

The devices can measure light levels ranging from 0.1 lux to 40,000 lux with no external circuitry required for signal conditioning. In ambient light-sensing applications, the integrating conversion technique used in both devices eliminates the effect of fluorescent flicker, thereby increasing the stability of the measurement. A single-supply operation (2.7 V to 3.3 V) makes both devices well suited for mobile applications. When the devices are not in use, a power down mode ensures that they consume as little power (10.8 uW) as possible.

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