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ISL29027IROZ-T7 데이터시트(PDF) 7 Page - Intersil Corporation |
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ISL29027IROZ-T7 데이터시트(HTML) 7 Page - Intersil Corporation |
7 / 13 page ISL29027 7 FN7815.0 February 7, 2011 Principles of Operation I2C Interface The ISL29027’s I2C interface slave address is internally hardwired as 0b100010<x>, where “0b” signifies binary notation and x represents the logic level on pin ADDR0. Figure 3 shows a sample one-byte read. The I2C bus master always drives the SCL (clock) line, while either the master or the slave can drive the SDA (data) line. Every I2C transaction begins with the master asserting a start condition (SDA falling while SCL remains high). The first transmitted byte is initiated by the master and includes 7 address bits and a R/W bit. The slave is responsible for pulling SDA low during the ACK bit after every transmitted byte. Each 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. Photodiodes and ADCs The ISL29027 contains photodiode arrays which convert photons (light) into current. The proximity sensor is an 8-bit ADC. When proximity sensing is enabled, the IRDR pin will drive a user- supplied infrared LED, the emitted IR reflects off an object (i.e., a human head) back into the ISL29027, and a sensor converts the reflected IR wave to a current signal in 0.54ms. The ADC subtracts the IR reading before and after the LED is driven (to remove ambient IR such as sunlight), and converts this value to a digital count stored in Register 0x8. Because of the conversion times, the user must let the ADCs perform one full conversion first before reading from I2C Registers PROX_DATA (wait 0.54ms). The proximity sensor runs continuously with a time between conversions decided by PROX_SLP (Register 1 Bits [6:4]).(as shown in Figure 4). Proximity Sensing When proximity sensing is enabled (PROX_EN = 1), the external IR LED is driven for 0.1ms by the built-in IR LED driver through the IRDR pin. The amplitude of the IR LED current depends on Register 1 bit 3: PROX_DR. If this bit is low, the load will see a TABLE 6. REGISTER 0x04 (PROX_HT) - INTERRUPT HIGH THRESHOLD FOR PROXIMITY SENSOR BIT # ACCESS DEFAULT BIT NAME FUNCTION/OPERATION 7:0 RW 0xFF PROX_HT (Prox Threshold) 8-bit interrupt high threshold for proximity sensing TABLE 7. REGISTER 0x08 (PROX_DATA) - PROXIMITY SENSOR DATA BIT # ACCESS DEFAULT BIT NAME FUNCTION/OPERATION 7:0 RO 0x00 PROX_DATA (Proximity Data) Results of 8-bit proximity sensor ADC conversion TABLE 8. REGISTER 0x0E (TEST1) - TEST MODE BIT # ACCESS DEFAULT BIT NAME FUNCTION/OPERATION 7:0 RW 0x00 (Write as 0x00) Test mode register. When 0x00, in normal operation TABLE 9. REGISTER 0x0F (TEST2) - TEST MODE 2 BIT # ACCESS DEFAULT BIT NAME FUNCTION/OPERATION 7:0 RW 0x00 (Write as 0x00) Test mode register. When 0x00, in normal operation FIGURE 3. I2C DRIVER TIMING DIAGRAM FOR MASTER AND SLAVE CONNECTED TO COMMON BUS START W A A A6 A5 A4 A3 A2 A1 A0 W A R7 R6 R5 R4 R3 R2 R1 R0 A A6 A5 A4 A3 A2 A1 A0 W A A A A D7 D6 D5 D4 D3D2 D1D0 13 5 7 13 57 1 2 3 4 5 6 9 2 4 6 STOP START SDA DRIVEN BY MASTER DEVICE ADDRESS SDA DRIVEN BY ISL29027 DATA BYTE0 REGISTER ADDRESS SLAVE DEVICE ADDRESS I2C DATA SDA DRIVEN BY MASTER SDA DRIVEN BY MASTER 24 68 9 2 468 9 7 8 1 3 5 7 8 9 I2C SDA I2C SDA I2C CLK MASTER (ISL29027) FIGURE 4. CURRENT DRIVE MODE OPTIONS PROX SENSOR ACTIVE IRDR (CURRENT DRIVER) 0.54ms FOR PROX CONVERSION SERIES OF CURRENT PULSES TOTALING 0.1ms SLEEP TIME (PROX_SLP) TIME TIME |
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