Proximity and ambient light sensor

Paul Boughton

The Optoelectronics group of Vishay Intertechnology Inc hs introduced a new fully integrated proximity and ambient light sensor featuring Filtron technology in one of the market's smallest surface-mount packages.

Measuring only 4mm by 2mm by 1.1mm, the VCNL4040 combines an IR emitter, photo detectors for proximity and ambient light, a signal processing IC, and a 16-bit ADC.

The three-in-one sensor features an interrupt function, supports I²C bus communication interface, and greatly simplifies window and sensor placement in a wide variety of consumer applications.

For smartphones, tablets, digital cameras, and other handheld consumer electronics, the Vishay Semiconductors VCNL4040 saves power as a proximity sensor by disabling touch screens until a user is detected and uses its integrated ambient light function for display/keypad adaptive brightness control and backlighting.

Containing the circuitry needed for these applications in one device, the VCNL4040 eliminates the need for additional light barriers and optical alignment of the IR emitter and photo diode.

With its small outline and low height, the VCNL4040 saves space in compact end products and gives design engineers greater flexibility in where and how they locate the sensor. For additional flexibility, the device can function at any depth or air gap below the glass window, unlike sensors with 8-, 10-, and 12-bit resolutions that require depths or air gaps of 1.5 mm or less.

Lower-resolution devices must also be placed away from other components on a costly and dedicated flexible circuit, while the 16-bit resolution of the VCNL4040 allows it to be assembled on the main PCB.

The VCNL4040's ambient light and proximity sensors operate in a parallel structure, and each offers a programmable interrupt function with high and low thresholds to lower power consumption.

The device's Filtron technology enables ambient light spectral sensitivity close to that of the human eye while offering excellent background light cancellation capabilities (including sunlight) without utilising the microprocessor, thereby enabling further power savings. 

With accuracy of ± 10%, the VCNL4040's built-in ambient light photo diode offers detection from 0.01 lx to 5.2 klx, allowing the device to operate in applications with dark or transparent window designs. The sensor offers fluorescent light flicker immunity and excellent temperature compensation from -40 °C to +85°C. 

Featuring selectable 12-bit and 16-bit outputs, the VCNL4040's proximity sensor uses intelligent cancellation to eliminate cross-talk, while a smart persistence scheme ensures accurate sensing and faster response time. The emitter wavelength peaks at 940nm and has no visible ‘red-tail’.

The device offers a supply voltage range of 2.5V to 3.6V and I²C bus voltage range from 1.8V to 3.3V. 

Offered in a lead-free 8-pin molded package, the sensor is RoHS-compliant, halogen-free, and Vishay GREEN.