Miniature ambient light sensors for smartphone displays

2nd February 2021

Alex Lynn

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Datasheet

ams has announced the TSL2520 and TSL2521 ambient light sensors which fit in a tiny bezel or gap to enable a smartphone’s screen to stretch from edge-to-edge of the chassis with no aperture. By using the TSL2520/21 to maximise the viewable screen area, smartphone manufacturers can provide the best possible user experience while enabling effective camera image correction.

The ams TSL2520 is an ambient light sensor (ALS) which features four photodiodes for visible light sensing and two infrared photodiodes, a combination which allows for rejection of IR interference and produces very accurate measurements of ambient light intensity (lux). The photodiodes are placed at the end of the sensor’s 2x1x0.5mm package, which means that the device can be positioned at the gap between the display screen and the chassis of the phone to maximise the screen-to-body ratio.

The TSL2521 provides the same ALS function and the identical mechanical specifications as the TSL2520 but also offers flicker detection capability. Sensing flicker in artificial light sources such as LEDs at frequencies up to 7kHz, the TSL2521 provides an image correction input to the phone’s camera. This enables the camera to eliminate banding and other flicker-generated artefacts that can distort captured images and videos.

The sensors’ accuracy and high sensitivity, measuring ambient light levels down to just 1mlux, support responsive display brightness management and help improve camera image quality.

Jian Liu, Strategic Program Director in the Integrated Optical Sensors business line at ams, said: “ams offers the industry’s widest portfolio of optical sensors for display management and camera management in mobile phones. This latest offering, which provides discrete ambient light and flicker sensing capabilities, extends the choices available to phone manufacturers even further, enabling them to further expand the boundaries of smartphone screen-to-body ratio and display management performance.”

Adding to the design flexibility which ams optical sensors afford, the TSL2520/21 products feature programmable gain which gives a dynamic range of 8192x. This means that the sensors can operate under any glass types and inks with any degree of light attenuation without requiring a visible aperture in the display glass.

Operating from a 1.8V supply and featuring configurable sleep modes, the TSL2520/21 sensors offer low power consumption to extend the run-time of the phone’s battery.

The TSL2520 and TSL2521 are available for sampling.