The TSL245 infrared light-to-frequency converter combines a silicon photodiode and a current-to-frequency converter on a single monolithic CMOS integrated circuit. The output is a square wave (50% duty cycle) with frequency directly proportional to light intensity. Because the output is TTL compatible, it allows direct interface to a microcontroller or other logic circuitry. The device responds over the infrared light range of 800 nm to 1100 nm. The TSL245 is characterized for operation over the temperature range of 25C to 70C. The TSL245 is offered in a black, infrared-transmissive package (see Figure 1). The photodiode area is 1.36 mm2 (0.0029 in2).