Sensor replicates optical response of the human eye

The MAX44000 IC was developed using Maxim's proprietary BiCMOS technology and integrates three optical sensors, two a/d converters and digital functionality into a 2 x 2 x 0.6mm package. According to Maxim, this integration saves board space while delivering optical fusion and 'unparalleled' light sensing performance. The device consumes 5µA when the ambient sensor is enabled and 7µA when both the proximity sensor and ambient light sensor are activated. It is designed for touch screen applications such as smartphones, portable devices, industrial sensors and presence detection. Presence detection allows a touch screen to shut off if a smartphone is brought up to a user's face and prevents inadvertent touches that may disrupt a call. Once an object has been 'sensed' within a certain distance, it is run through a dc ambient infrared rejection front end circuit and sent to an a/d converter. This process, says Maxim, allows the MAX44000 to operate in the presence of large amounts of dc IR radiation. And, 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. According to Maxim, traditional light sensors are strongly influenced by UV and IR light which are not perceptible by the human eye and sensing this light leads to inaccurate ambient light readings. The company claims its BiCMOS technology enables the integration of the two photodiodes and an optical filter to reject UV and IR light. This, it adds, allows the MAX44000 to replicate the optical response of the human eye in a variety of environments.