TSL237S - Light to Frequency Converter
The TSL237S-LF 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. Because it is TTL compatible, the digital output allows direct interface to a microcontroller or other logic circuitry. The device has been temperature compensated for the ultraviolet-to-visible light range of 320 nm to 700 nm and responds over the light range of 320 nm to 1050 nm. The TSL237 is characterized for operation over the temperature range of −40°C to +70°C and is supplied in a 3-lead clear plastic side-looker package with an integral lens.
Light-to-Frequency Converter Features
- High-resolution conversion of light intensity to frequency with no external components
- High irradiance responsivity: 2.3 kHz/(µW/cm²) at λp = 524 nm
- Low dark frequency: Less than 2 Hz at 50°C
- Communicates directly With a microcontroller
- Compact three-lead clear plastic package
- Single-supply operation from 2.7V to 5.5V DC
- Typical current draw: 2 mA
- Stable 200 ppm/°C temperature coefficient
- Output frequency: 40 to 60 kHz
- Nonlinearity error typically 0.2% at 100 kHz
- Note: Power-supply lines must be decoupled by a 0.01 µF to 0.1 µF capacitor with short leads placed close to the TSL237. The output of the device is designed to drive a standard TTL or CMOS logic input over short distances. If lines greater than 12 inches are used on the output, a buffer or line driver is recommended.
