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TSL238T Light-to-Frequency

High-sensitivity converter low profile 4-pin package


  • 850K:1 input dynamic range
  • Low dark frequency (0.6Hz typical)
  • 2.6mm x 3.8mm 4-lead SMD (T) package


  • Detects light intensity at a high resolution
  • Provides low light level operation
  • Reduces board space requirements while simplifying designs

Product parameters

Supply Voltage [V] 2.7-5.5
Responsivity [Hz/µW/cm²] 3400 @ 640
Max. Output Frequency [MHz] 1
Selectable Sensitivity and Full-Scale Output Frequency
Output Frequency Tolerances [+/- %] 20
Temperature Range [°C] -40 to 85
Packages T
Remark Not recommended for new design. Please see Ambient Light Sensors device family.

General Description

The TSL238T 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. Output enable (OE) places the output in a high-impedance state for multiple-unit sharing of a microcontroller input line. 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 TSL238T is characterized for operation over the temperature range of −40°C to 85°C and is supplied in a compact 4-lead surface-mount package that is lead (Pb) free and RoHS compliant.

This product suits for the following applications:

  • Pulse oximetry
  • Turbidity sensing
  • Optical switch


Title Category Headline Buy
Light-to-FrequencyEvalKit Application Board Evaluation Kit for Light-to-Frequency Sensors

Technical Documents

Name Type Description Version Language
LightSensors_AN000519_1-00.pdf Application Note Colorimetry Tutorial (DN 20) 1-00 English
TSL238T_BD000188_1-00.png Block Diagram TSL238T Block Diagram 1-00 English
TSL238T_DS000130_2-00.pdf Datasheet Document version 1-00 2-00 English
TSL235R_TSL237_TSL237T_TSL238T_PD000365_1-00.png Other Product Document Light-to-FrequencyEvalKit Image 1-00 English

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