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ISL29023IROZ-T7 датащи(PDF) 5 Page - Intersil Corporation |
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ISL29023IROZ-T7 датащи(HTML) 5 Page - Intersil Corporation |
5 / 14 page ISL29023 5 FN6691.4 May 1, 2014 Submit Document Feedback Principles of Operation Photodiodes and ADC The ISL29023 contains two photodiode arrays, which convert light into current. The spectral response for ambient light sensing and IR sensing is shown in Figure 4, on page 4. After light is converted to current during the light signal process, the current output is converted to digital by a built-in 16-bit Analog-to-Digital Converter (ADC). An I2C command reads the ambient light or IR intensity in counts. The converter is a charge-balancing integrating type 16-bit ADC. The chosen method for conversion is best for converting small current signals in the presence of an AC periodic noise. A 100ms integration time, for instance, highly rejects 50Hz and 60Hz power line noise simultaneously. The built-in ADC offers user flexibility in integration time or conversion time. There are two timing modes: Internal Timing Mode and External Timing Mode. In Internal Timing Mode, integration time is determined by an internal oscillator (fOSC), and the n-bit (n = 4, 8, 12, 16) counter inside the ADC. In External Timing Mode, integration time is determined by the time between two consecutive I2C External Timing Mode commands. A good balancing act of integration time and resolution (depending on the application) is required for optimal results. The ADC has I2C programmable range select to dynamically accommodate various lighting conditions. For very dim conditions, the ADC can be configured at its lowest range (Range 1) in the ambient light sensing. Low-Power Operation The ISL29023 initial operation is at the power-down mode after a supply voltage is provided. The data registers contain the default value of 0. When the ISL29023 receives an I2C command to do a one-time measurement from an I2C master, it will start the ADC conversion with light sensing. It will go into power-down mode automatically after one conversion is finished and keep the conversion data available for the master to fetch anytime afterwards. The ISL29023 will continuously do ADC conversion with light sensing if it receives an I2C command of continuous measurement. It will continuously update the data registers with the latest conversion data. It will go into power-down mode after it receives the I2C command. Ambient Light and IR Sensing There are four operational modes in ISL29023: Programmable ALS once with auto power-down, programmable IR sensing once with auto power-down, programmable continuous ALS sensing and programmable continuous IR sensing. These four modes can be programmed in series to fulfill the application needs. The detailed program configuration is listed in “Command-I Register (Address: 0x00)” on page 8. When the part is programmed for ambient light sensing, the ambient light with wavelength within the “Ambient Light Sensing” spectral response curve in Figure 4 is converted into current. With ADC, the current is converted to an unsigned n-bit (up to 16 bits) digital output. When the part is programmed for infrared (IR) sensing, the IR light with wavelength within the “IR Sensing” spectral response curve in Figure 4 is converted into current. With ADC, the current is converted to an unsigned n-bit (up to 16-bits) digital output. Interrupt Function The active low interrupt pin is an open drain pull-down configuration. The interrupt pin serves as an alarm or monitoring function to determine whether the ambient light level exceeds the upper threshold or goes below the lower threshold. It should be noted that the function of ADC conversion continues without stopping after interrupt is asserted. If the user needs to read the ADC count that triggers the interrupt, the reading should be done before the data registers are refreshed by the following conversions. The user can also configure the persistency of the interrupt pin. This reduces the possibility of false triggers, such as noise or sudden spikes in ambient light conditions. An unexpected camera flash, for example, can be ignored by setting the persistency to 8 integration cycles. FIGURE 9. SUPPLY CURRENT vs TEMPERATURE IN ALS SENSING Typical Performance Curves (Continued) 60 65 70 75 80 85 90 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) ALS SENSING 10,000 Lux |
Аналогичный номер детали - ISL29023IROZ-T7 |
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Аналогичное описание - ISL29023IROZ-T7 |
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