The TSL245R light-to-frequency converter combines a silicon photodiode and a current-to-frequency converter on a single monolithic CMOS integrated circuit. Output is a square wave (50% duty cycle) with frequency directly proportional to light intensity (irradiance) on the photodiode. The digital output allows direct interface to a microcontroller or other logic circuitry. The TSL245R is characterized for operation over the temperature range of - 25C to 70C and is supplied in a 3-lead plastic side-looker package with an integral visible-light cutoff filter and lens. When supplied in the lead (Pb) free package, the devices are RoHS compliant.