Texas Instruments OPT4041DTSR

The OPT4041 is a light-to-digital sensor (single chip lux meter) that measures the intensity of visible light in two independent channels. The spectral response of the ALS channel tightly matches the photopic response of the human eye, where as the spectral response of the WB channel is wide and measures a broad spectrum of light. A specially engineered filter on the ALS channel rejects near-infrared component from common light sources to measure accurate light intensity. The output of the OPT4041 is semi-logarithmic with binary logarithmic full-scale light ranges along with a highly linear response within each range. The visible channel provides nine binary light ranges, providing measurement capability from 585µlux to 157klux and 28 bits of effective dynamic range. The wide band channel provides seven light ranges, providing measurement capability from 192.3pW/cm2 to 12.91mW/cm2 and 26 bits of effective dynamic range. The built-in automatic range selection logic dynamically adjusts the device gain settings based on the light level, providing the best possible resolution in all conditions without user input.

The OPT4041 is equipped with engineered optical filters on both channels, providing strong out-of-band rejection. Strong infrared rejection on the visible channel aids in maintaining high lux accuracy across all light sources, especially when the sensor is placed under dark glass for aesthetic reasons. The WB channel provides a wide spectrum response helping measure a wide range of spectral content including NIR wavelengths 850nm and 940nm.

The OPT4041 is designed for systems that require light level detection to enhance user experience and typically replaces low-accuracy photodiodes, photoresistors, and other ambient light sensors with underwhelming human eye matching and near-infrared rejection.

The OPT4041 device can be configured to operate with light conversion times from 600µs to 800ms per channel in 12 steps, providing system flexibility based on application need. Conversion time includes the light integration time and analog-to-digital (ADC) conversion time. Measurement resolution is determined by a combination of light intensity and integration time, effectively providing the capability to measure down to 585µlux of light intensity changes.

Digital operation is flexible for system integration. Measurements can be either continuous or triggered in one shot with register writes or a hardware pin. The device features a threshold detection logic, which allows the processor to sleep while the sensor waits for an appropriate wake-up event to report through the interrupt pin.

The sensor reports a digital output representing the light level over an I2C- and SMBus-compatible, two-wire serial interface. An internal first-in-first-out (FIFO) on the output registers is available to read out measurements from the sensor at a slower pace while still preserving all data captured by the device. The OPT4041 also supports I2C burst mode, thus helping the host read data from the FIFO with minimal I2C overhead.

The low power consumption and low power-supply voltage capability of the OPT4041 helps enhance the battery life of battery-powered systems.