Ambient light & proximity sensor saves battery power

20th February 2015
Source: Vishay
Posted By : Nat Bowers
Ambient light & proximity sensor saves battery power

Integrating an IR emitter, photo detectors for proximity and ambient light, a signal processing IC and a 16-bit ADC, the VCNL4040 has been introduced by Vishay Intertechnology. The three-in-one sensor 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.

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, including smartphones, tablets and digital cameras. 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. The device offers a supply voltage range of 2.5-3.6V and I²C bus voltage range of 1.8-3.3V. 

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 1.5mm 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 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 MPU, enabling further power savings.

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

Offered in a lead-free 8-pin molded package measuring just 4x2x1.1mm, the sensor is RoHS-compliant, halogen-free and Vishay GREEN. Samples and production quantities are available now, with lead times of six to eight weeks for large orders.

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