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ISL29015IROZ-EVALZ Folha de dados(PDF) 4 Page - Intersil Corporation |
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ISL29015IROZ-EVALZ Folha de dados(HTML) 4 Page - Intersil Corporation |
4 / 13 page 4 FN6522.0 October 31, 2008 Principles of Operation Photodiodes and ADC The ISL29015 contains two photodiode arrays which convert light into current. The spectral response for ambient light sensing and IR sensing is shown in Figure 6 in the performance curves section. 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. See “Integration and Conversion Time” on page 7. 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. For very bright conditions, the ADC can be configured at its highest range (Range 4) in the proximity sensing. Low-Power Operation The ISL29015 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 ISL29015 receives an I2C command to do a one-time measurement from an I2C master, it will start ADC conversion with light or proximity sensing. It will go to the power-down mode automatically after one conversion is finished and keep the conversion data available for the master to fetch anytime afterwards. The ISL29015 will continuously do ADC conversion with light or proximity 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 to the power-down mode after it receives the I2C command of power-down. Ambient Light, IR and Proximity Sensing There are six operational modes in ISL29015: Programmable ALS once with auto power-down, programmable IR sensing once with auto power-down, programmable proximity sensing once with auto power-down; programmable continuous ALS sensing, programmable continuous IR sensing and ISDA SDA Current Sinking Capability 4 5 mA IIRDR1 IRDR Source Current IS<1:0> = 0 (Note 4) 1.5V at IRDR pin 100 mA IIRDR2 IRDR Source Current IS<1:0> = 1 (Note 4) 44 50 56 mA IIRDR3 IRDR Source Current IS<1:0> = 2 (Note 4) 25 mA IIRDR4 IRDR Source Current IS<1:0> = 3 (Note 4) 12.5 mA VIRLED Voltage Head Room of IRDR Pin VDD - 0.6 V tr Rise Time for IRDR Source Current RLOAD = 15Ω at IRDR pin, 20% to 80% 35 ns tf Fall Time for IRDR Source Current RLOAD = 15Ω at IRDR pin, 80% to 20% 10 ns fIRLED1 IR LED Modulation Frequency Freq<1:0> = 0 (Note 4) DC kHz fIRLED2 IR LED Modulation Frequency Freq<1:0> = 3 (Note 4) 360 kHz IDD (IRLED1) Supply Current of Proximity Sensing IS<1:0> = 0, Freq<1:0> = 0 (Note 4) 101 mA IDD (IRLED2) Supply Current of Proximity Sensing IS<1:0> = 0, Freq<1:0> = 3 (Note 4) 51 mA Duty Cycle Duty Cycle of IR LED Modulation 50 % PROX-IR PROX Differential ADC Output of IR and Proximity Sensing With Object Far Away to Provide No Reflection IR and proximity sensing with Range 2; 1.5V @ IRDR pin, IS<1:0> = 0, Freq<1:0> = 0; E = 210 lux, Sunlight. 2.0 % NOTES: 2. 550nm green LED is used in production test. The 550nm LED irradiance is calibrated to produce the same DATA count against an illuminance level of 300 lux fluorescent light. 3. 850nm infrared LED is used in production test. The 850nm LED irradiance is calibrated to produce the same DATA_IR count against an illuminance level of 210 lux sunlight at sea level. 4. See “Register Set” on page 6. Electrical Specifications VDD = 3V, TA = +25°C, REXT = 499kΩ 1% tolerance, 16-bit ADC operation, unless otherwise specified. (Continued) PARAMETER DESCRIPTION CONDITION MIN TYP MAX UNIT ISL29015 |
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