Proximity and ambient light optical sensor offers 16-bit resolution

June 18, 2012 // By Paul Buckley
Vishay Intertechnology, Inc. has introduced a new fully integrated proximity and ambient light optical sensor with the industry’s lowest height of 0.8 mm.

The VCNL4020 combines an IR emitter, a photo-pin-diode for proximity, an ambient light detector, a signal processing IC, and a 16-bit ADC in one small 4.8 mm x 2.3 mm x 0.8 mm rectangular leadless (LLP) package. The 3-in-1 sensor features an interrupt function, supports I2C bus communication interface, and greatly simplifies window and sensor placement in a wide variety of consumer and industrial applications.

For mobile devices such as smart phones, touch phones, PDAs, GPS units, and digital cameras, the new VCNL4020 saves power as a proximity sensor by turning off the display backlight when close to the user, while using its integrated ambient light function for display/keypad adaptive brightness control. Containing all the circuitry needed for these applications in one device, the VCNL4020 eliminates the need for additional light barriers and optical alignment of the IR emitter and photo diode.

While other devices with similar features use chip on printed circuit board technology that results in package heights of 1.2 mm or greater, the VCNL4020 uses a proprietary technology that delivers the lowest height on the market. This gives design engineers greater flexibility in where and how they locate the sensor. For additional flexibility, the VCNL4020 can function at any depth or air gap below the glass window, unlike devices 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. The 16-bit resolution of the VCNL4020 allows it to be assembled on the main PCB near other components, ensures excellent cross talk immunity, and is especially important given that windows above the sensor absorb typically 90% of the infrared emission.

The VCNL4020’s interrupt function enables the sensor to work independently until a predefined proximity or ambient light event occurs, and then it wakes up the microcontroller. This helps customers reduce their software effort and