TSL237 Light to Frequency Converter

The TSL237 light-to-frequency converter (High Responsivity) 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 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.

Features:

• Communicates directly with a microcontroller - Arduino, Basic Stamp, Propeller, 8051, PIC, ATmega
  
• Single-supply operation
• Compact 3-lead clear plastic package
• High-resolution conversion of light intensity to frequency with no external components

Suggested Applications:

• Camera exposure
• Dimming displays
• Machine vision

Key Specifications:

• Nonlinearity Error (Typically 0.2% at 100 kHz)
• Stable 150ppm/° C Temperature Coefficient
• Supply Voltage 2.7 - 5.5 VDC
• Operating Temperature range -25 - 70 C
• Typical current draw 2 mA
• Output Frequency 40 - 60 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 TSL235R. 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.