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OPT3007 bảng dữ liệu(PDF) 11 Page - Texas Instruments |
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OPT3007 bảng dữ liệu(HTML) 11 Page - Texas Instruments |
11 / 39 page 11 OPT3007 www.ti.com SBOS864 – AUGUST 2017 Product Folder Links: OPT3007 Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated 7.3 Feature Description 7.3.1 Human Eye Matching The OPT3007 spectral response closely matches that of the human eye. If the ambient light sensor measurement is used to help create a good human experience, or create optical conditions that are optimal for a human, the sensor must measure the same spectrum of light that a human sees. The device also has excellent infrared light (IR) rejection. This IR rejection is especially important because many real-world lighting sources have significant infrared content that humans do not see. If the sensor measures infrared light that the human eye does not see, then a true human experience is not accurately represented. Furthermore, if the ambient light sensor is hidden underneath a dark window (such that the end-product user cannot see the sensor) the infrared rejection of the OPT3007 becomes significantly more important because many dark windows attenuate visible light but transmit infrared light. This attenuation of visible light and lack of attenuation of IR light amplifies the ratio of the infrared light to visible light that illuminates the sensor. Results can still be well matched to the human eye under this condition because of the high infrared rejection of the OPT3007. 7.3.2 Automatic Full-Scale Range Setting The OPT3007 has an automatic full-scale range setting feature that eliminates the need to predict and set the optimal range for the device. In this mode, the OPT3007 automatically selects the optimal full-scale range for the given lighting condition. The OPT3007 has a high degree of result matching between the full-scale range settings. This matching eliminates the problem of varying results or the need for range-specific, user-calibrated gain factors when different full-scale ranges are chosen. For further details, see the Automatic Full-Scale Setting Mode section. 7.3.3 I2C Bus Overview The OPT3007 offers compatibility with both I2C and SMBus interfaces. The I2C and SMBus protocols are essentially compatible with one another. The I2C interface is used throughout this document as the primary example with the SMBus protocol specified only when a difference between the two protocols is discussed. The OPT3007 is connected to the bus with two pins: an SCL clock input pin and an SDA open-drain bidirectional data pin. The bus must be controlled by a master device that generates the serial clock (SCL), controls the bus access, and generates start and stop conditions. To address a specific device, the master initiates a start condition by pulling the data signal line (SDA) from a high logic level to a low logic level while SCL is high. All slaves on the bus shift in the slave address byte on the SCL rising edge, with the last bit indicating whether a read or write operation is intended. During the ninth clock pulse, the slave being addressed responds to the master by generating an acknowledge bit by pulling SDA low. Data transfer is then initiated and eight bits of data are sent, followed by an acknowledge bit. During data transfer, SDA must remain stable while SCL is high. Any change in SDA while SCL is high is interpreted as a start or stop condition. When all data are transferred, the master generates a stop condition, indicated by pulling SDA from low to high while SCL is high. The OPT3007 includes a 28-ms timeout on the I2C interface to prevent locking up the bus. If the SCL line is held low for this duration of time, the bus state machine is reset. 7.3.3.1 Serial Bus Address To communicate with the OPT3007, the master must first initiate an I2C start command. Then, the master must address slave devices via a slave address byte. The slave address byte consists of a seven bit address 1000101 and a direction bit that indicates whether the action is to be a read or write operation. 7.3.3.2 Serial Interface The OPT3007 operates as a slave device on both the I2C bus and SMBus. Connections to the bus are made via the SCL clock input line and the SDA open-drain I/O line. The OPT3007 supports the transmission protocol for standard mode (up to 100 kHz), fast mode (up to 400 kHz), and high-speed mode (up to 2.6 MHz). All data bytes are transmitted most-significant bits first. The SDA and SCL pins feature integrated spike-suppression filters and Schmitt triggers to minimize the effects of input spikes and bus noise. See the Electrical Interface section for further details of the I2C bus noise immunity. |
Số phần tương tự - OPT3007 |
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Mô tả tương tự - OPT3007 |
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