TSL237T - High-Sensitivity Light-to-Frequency Converters - The TSL237, TSL237T High-Sensitivity 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 it is TTL compatible, the output allows direct interface to a microcontroller or other logic circuitry. The TSL237, TSL237T have been temperature compensated for the ultraviolet-to-visible range of 320 nm to 700 nm and responds over the light range of 320 nm to 1050 nm. The device is characterized for operation over the temperature range of -40 degrees C to 85 degrees C.