Light converter transforms intensity to digital
By Bill Schweber -- EDN, March 31, 2005
Targeting display-panel-backlighting-control applications, the single-chip TSL2560 and similar TSL2561 devices from Texas Advanced Optoelectronic Solutions handle wide ambient-light range and a broadband spectrum. The TSL2560 features an SMBus interface, well-matched to notebook and tablet PCs, and the TSL2561 uses the I2C interface, which is more common in LCD monitors, flat-panel TVs, and cell phones (Picture).
Both devices incorporate a broadband diode for the visible-light spectrum and some IR sensitivity, plus a mostly IR photodiode, and they then simultaneously integrate and digitize the currents from each sensor using two A/D converters, which also reject 50/60-Hz lighting ripple. This channel-and-converter pairing yields 20-bit dynamic range—with 16-bit resolution but without a relatively costly optical filter—over 0.1 to 40,000 lux. The single-supply, 2.7 to 3.3V ICs support an interrupt feature, whereby the system processor need not poll for the latest intensity value; instead, the IC interrupts when there is a significant, user-defined change.
The six-pin devices are available in a 1.7×1.2×0.7-mm chip-scale version or in a 3.8×2.6×1.4-mm, transfer-molded board variation for $1.29 (1000).
Texas Advanced Optoelectronic Solutions, www.taosinc.com.
