Optical sensor from Maxim combines ambient light and proximity sensors

The device also consumes very low power: only 5µA when the ambient sensor is enabled, and only 7µA when both the proximity sensor and ambient light sensor are activated, and as a result significantly extends an application’s battery life. The MAX44000 has been designed for touch-screen applications, including smartphones, portable devices, industrial sensors, and presence detection.

When a smartphone is brought up to a user’s face, the touch screen must be shut off to prevent inadvertent touches that may disrupt the call. A proximity sensor is therefore crucial, so the phone can “sense” an object is within a certain distance during a call or any other preset event. Once a sensed signal is received, it is run through a DC ambient, infrared (IR) rejection front-end circuit and sent to an ADC. This process allows the MAX44000 to operate in the presence of large amounts of DC IR radiation. By using a single-pulse technique for pulsing the external IR LED, the sensor is immune to fixed-frequency external IR radiation. This immunity leads to more reliable sensor operation.

Traditional light sensors are strongly influenced by ultraviolet (UV) and IR light, which are not perceptible by the human eye. Sensing this light leads to inaccurate ambient-light readings. Maxim’s BiCMOS technology enables the integration of the two photodiodes and an optical filter to reject UV and IR light. This allows the MAX44000 to replicate the optical response of the human eye in a variety of environments.

Maxim Integrated Products

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