New Miniature Ambient Light Sensors for Edge-to-Edge Smartphone Displays

By Tiera Oliver

Assistant Editor

Embedded Computing Design

February 02, 2021


New Miniature Ambient Light Sensors for Edge-to-Edge Smartphone Displays

ams announced the TSL2520 and TSL2521 ambient light sensors designed to 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 maximize the viewable screen area, smartphone manufacturers can provide ideal 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 measurements of ambient light intensity (lux). The photodiodes are placed at the end of the sensor’s 2mm x 1mm x 0.5mm package, the smallest in the market according to the company, which means that the device can be positioned at the gap between the display screen and the chassis of the phone to maximize 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. Adding to the design flexibility which ams optical sensors afford, the TSL2520/21 products feature programmable gain which gives a dynamic range of 8192x. Per the company, 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.

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Tiera Oliver, Assistant Editor for Embedded Computing Design, is responsible for web content edits and constructing stories. She also assists with newsletter updates as well as contributing and editing content for ECD podcasts and the ECD YouTube channel. Before working at ECD, Tiera graduated from Northern Arizona University where she received her B.S. in journalism and political science and worked as a news reporter for the university’s student led newspaper, The Lumberjack.

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