The ams TCS3701 enables front-facing ambient light and proximity sensing measurements in smartphones – maximizing edge-to-edge display screen size – with sensor operations under the OLED display. By developing this ‘Behind OLED’ ambient light/proximity sensor, ams enables smartphone manufacturers to achieve the highest possible ratio of display area to body size while retaining crucial touchscreen disablement and automatic display brightness/color adjustment functions, which require an RGB/infrared light sensor.

The TCS3701 senses the addition of the ambient light passing through the display to light emitted by the display’s pixels located just above the sensor. ams has developed unique algorithms which enable accurate detection of ambient light levels without knowledge of the display pixel brightness above the sensor.

The TCS3701 enables phone designers to maximize their products’ screen-to-body ratio as much as possible on the display’s face. Furthermore, the TCS3701 can potentially eliminate the bezel entirely. This is only possible because the TCS3701 can operate behind an OLED display, a breakthrough enabled by the outstanding sensitivity of the device and by the implementation of sophisticated measurement algorithms to compensate for the optical distortion caused by the OLED display.

ams’ TCS3701 is a high sensitivity light-to-digital converter that features ambient light and color (RGB) sensing in parallel with IR proximity detection. This capability supports today’s industrial design trend of maximizing the smartphone display area by eliminating front-facing bezels, where an ambient light/proximity sensor is typically located. The ambient light and color sensing function provides five concurrent ambient light sensing channels: Red, Green, Blue, Clear, and Wideband. The RGB and Clear channels have a UV/IR blocking filter.

The ams TCS3701 accurately measures the intensity of ambient light from behind an OLED screen and enables the calculation of illuminance, chromaticity, and color temperature to manage display appearance. The proximity function synchronizes IR emission and detection to sense nearby objects. The IR driver needs to be connected to an external LED or VCSEL emitter. The architecture of the engine features self-maximizing dynamic range, ambient light subtraction, advanced optical crosstalk noise cancellation, 14-bit data output and interrupt-driven 1.8V I²C communications interface. Sensitivity, power consumption, and noise can be optimized with adjustable IR LED timing and power. The proximity engine recognizes detect/release events and produces a configurable interrupt whenever the proximity result crosses upper or lower threshold settings.

The TCS3701’s 2.0mm x 2.5mm x 0.5mm OQFN package is small enough to be placed behind a smartphone’s OLED screen. It gives a smartphone designer the flexibility to mount an IR emitter to support the proximity sensing function in the best front-facing location. Cross-talk compensation algorithms provide for reliable proximity sensing performance.

TCS3701 integrates multiple applications within one device, including the following:
o Brightness management for displays
o Color management for displays
o Proximity detection
o Touch screen disable
o Display backlight control
o Display management
o Ambient light sensing
o Color temperature sensing to assist backlight, camera, and flash control

TCS3701 Color and Proximity Sensor PDF