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ISL29033IROZ-EVALZ Datasheet(PDF) 10 Page - Intersil Corporation |
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ISL29033IROZ-EVALZ Datasheet(HTML) 10 Page - Intersil Corporation |
10 / 15 page ISL29033 10 FN7656.2 February 25, 2013 External Scaling Resistor REXT for fOSC and Range The ISL29033 uses an external resistor, REXT, to fix its internal oscillator frequency, fOSC, and the light sensing range, Range. The fOSC and Range are inversely proportional to REXT. For ease of use, the proportionality constant is referenced to 499kΩ. Calculation for Range is shown in Equation 5 and for fOSC in Equation 6. Noise Rejection In general, integrating-type ADCs have excellent noise rejection characteristics for periodic noise sources for which frequency is an integer multiple of the conversion rate. For example, a 60Hz AC unwanted signal’s sum from 0ms to k*16.66ms (k = 1,2...ki) is zero. Similarly, setting the device’s integration time to be an integer multiple of the periodic noise signal greatly improves the light sensor output signal in the presence of noise. ADC Output in IR Sensing The ISL29033 ADC output codes, DATA, are directly proportional to the IR intensity received in IR sensing, as shown in Equation 7. In this equation, EIR is the received IR intensity. The constant, b, changes with the spectrum of background IR noise, such as sunlight and incandescent light. The constant, b, also changes with ADC range and resolution selections. Suggested PCB Footprint It is important that users check Tech Brief 477, “Surface Mount Assembly Guidelines for Optical Dual FlatPack No Lead (ODFN) Package” before starting ODFN product board mounting: http://www.intersil.com/data/tb/TB477.pdf Layout Considerations The ISL29033 is relatively insensitive to layout. Like other I2C devices, it is intended to provide excellent performance even in significantly noisy environments. Attention to a few considerations will ensure best performance. Route the supply and I2C traces as far as possible from all sources of noise. Use two power-supply decoupling capacitors, 1µF and 0.1µF, placed close to the device. Typical Circuit A typical application for the ISL29033 is shown in Figure 5. The ISL29033 I2C address is internally hardwired as 1000100. The device can be tied onto a system’s I2C bus together with other I2C compliant devices. Soldering Considerations Convection heating is recommended for reflow soldering; direct-infrared heating is not recommended. The plastic ODFN package does not require a custom reflow soldering profile; it is qualified to +260°C. A standard reflow soldering profile with a +260°C maximum is recommended. ALS Sensor Window Layout Special care should be taken to ensure that the sensor, as shown in the sensor location outline (Figure 6), is uniformly illuminated. Shadows from off-angle window openings can affect uniform illumination, which in turn can affect measurement results. TABLE 8. INTEGRATION TIME OF n-BIT ADC REXT (kΩ) n = 16-BIT (ms) n = 12-BIT (ms) n = 8-BIT (µs) n = 4-BIT (µs) 499 100 6.25 391 24 1000 200 12.5 782 48 (EQ. 5) Range 499k Ω REXT ------------------- Range k () × = (EQ. 6) fOSC 499k Ω REXT ------------------- 655 × kHz = DATAIR β EIR × = (EQ. 7) |
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