Light Sensor Chips

Light sensor chips convert light into electrical signals which are then conditioned to produce a desired electrical output. They are sometimes called light-to-frequency chips, light-to-voltage chips, or ambient light sensors. Light sensor chips are used in power management applications to control dimming and extend the life of liquid crystal displays (LDC) for portable electronic devices such as cell phones, digital cameras, and notebook computers. There are two types of light sensor chips: phototransistors and photodiodes. Phototransistors amplify variations in light and output a voltage. They are more sensitive than photodiodes and may or may not have a base lead. Photodiodes are solid-state light detectors with a radiation-sensitive junction in semiconductor material. The base current from the incident photons is amplified by the gain of the transistor, resulting in current gains that range from hundreds to several thousands. Response time is a function of the capacitance of the collector-base junction and the value of the load resistance. Most photodiodes provide current outputs.

Light sensor chips differ in terms of performance specifications and mounting styles. Specifications for light sensors chips that use photo transistors include: collector current (mA), collector dark current (mA), peak wavelength (nm), rise time (ns), collector-emitter breakdown voltage (V), and power dissipation (mW). Parameters to consider also include spectral range, fall time, acceptable angle, and operating temperature. Proper thermal stability ensures that the output of light sensor chips is a function of changes in light and not changes in temperature. Performance specifications for light sensor chips that use photo diodes include sensitivity, rise time, quantum efficiency, and operating temperature. In terms of mounting styles, choices include surface mount technology (SMT) and through hole technology (THT). SMT adds components to a printed circuit board (PCB) by soldering component leads or terminals to the top surface of the board. Through hole technology (THT) mounts light sensor chips by inserting component leads through holes in the board and then soldering the leads in place on the opposite side of the board.

Light sensor chips that are destined for sale in Europe must comply with Restriction of Hazardous Substances (RoHS), a European Union (EU) directive that requires all manufacturers of electronic and electrical equipment to demonstrate that their products contain only minimal levels of the following hazardous substances: lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyl and polybrominated diphenyl ether. RoHS became effective on July 1, 2006.

• Sensor Sense: Grayscale Versus Color Vision Sensors
  The imager chip in a grayscale vision sensor acts like thousands of electronic light meters that measure light levels at specific points across an area. The light-sensitive elements, called...
  (read more)
• Bigger Role for 16-bit Chips Bigger role for 16-bit chips
  New chips make it easier for automakers to electronically control doors, seats, lighting, and HVAC Jim Williams, 16-Bit Applications Section Leader Eight-bit microcontrollers have historically handled...
  (read more)
• TSL2550 with Microcontroller
  The TSL2550 Ambient Light Sensor simplifies the acquisition of ambient light intensity and spectral content information through the use of on-board analog-to-digital conversion and SMBus interface....
  (read more)

Pages: 1 - 3 of 285

Part Numbers for Light Sensor Chips