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ISL29003 データシート(PDF) 3 Page - Intersil Corporation |
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ISL29003 データシート(HTML) 3 Page - Intersil Corporation |
3 / 15 page 3 FN7464.2 December 12, 2006 Principles of Operation Photodiodes The ISL29003 contains two photodiodes. Diode1 is sensitive to both visible and infrared light, while Diode2 is mostly sensitive to infrared light. The spectral response of the two diodes are independent from one another. See Figure 7 Spectral Response vs Wavelength in the performance curves section. The photodiodes convert light to current. Then, the diodes’ current outputs are converted to digital by a single built-in integrating type 16-bit Analog-to-Digital Converter (ADC). An I2C command mode determines which photodiode will be converted to a digital signal. Mode1 is Diode1 only. Mode2 is Diode2 only. Mode3 is a sequential Mode1 and Mode2 with an internal subtract function (Diode1 - Diode2). Analog-to-Digital Converter (ADC) 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. See Integration Time and Noise Rejection section. The built-in ADC offers user flexibility in integration time or conversion time. Two timing modes are available. Internal Timing Mode and External Timing Mode. In Internal Timing Mode, integration time is determined by an internal dual speed 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 External Timing Mode example. A good balancing act of integration time and resolution depending on the application is required for optimal results. The ADC has four I2C programmable range select to dynamically accommodate various lighting conditions. For very dim conditions, the ADC can be configured at its lowest range. For very bright conditions, the ADC can be configured at its highest range. 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 exceeds the upper threshold or goes below the lower threshold. The user can also configure the persistency of the interrupt pin. This eliminates any 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. I2C Interface There are eight (8) 8-bit registers available inside the ISL29003. The command and control registers define the operation of the device. The command and control registers do not change until the registers are overwritten.There are two 8-bit registers that set the high and low interrupt thresholds. There are four 8-bit data Read Only registers. Two bytes for the sensor reading and another two bytes for the timer counts. The data registers contain the ADC's latest digital output, and the number of clock cycles in the previous integration period. The ISL29003’s I2C interface slave address is hardwired internally as 44(hex). Figure 1 shows a sample one-byte read. Figure 2 shows a sample one-byte write. Figure 3 shows a sync_iic timing diagram sample for externally controlled integration time. The I2C bus master always drives the SCL (clock) line, while either the master or the slave can drive the SDA (data) line. Figure 2 shows a sample write. Every I2C transaction begins with the master asserting a start condition (SDA falling while SCL remains high). The following byte is driven by the master, and includes the slave address and read/write bit. The receiving device is responsible for pulling SDA low during the acknowledgement period. Every I2C transaction ends with the master asserting a stop condition (SDA rising while SCL remains high). For more information about the I2C standard, please consult the Philips® I2C specification documents. Pin Descriptions PIN NUMBER PIN NAME DESCRIPTION 1 VDD Positive supply; connect this pin to a regulated 2.5V to 3.3V supply 2 GND Ground pin. The thermal pad is connected to the GND pin 3 REXT External resistor pin for ADC reference; connect this pin to ground through a (nominal) 100k Ω resistor 4INT Interrupt pin; LO for interrupt/alarming. The INT pin is an open drain. 5SCL I2C serial clock The I2C bus lines can pulled above VDD, 5.5V max. 6SDA I2C serial data ISL29003 |
同様の部品番号 - ISL29003 |
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同様の説明 - ISL29003 |
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