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ISL29030AIROZ-T7 Datasheet(PDF) 10 Page - Intersil Corporation |
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ISL29030AIROZ-T7 Datasheet(HTML) 10 Page - Intersil Corporation |
10 / 16 page ISL29030A 10 FN7722.2 November 12, 2012 When the IR from the LED reaches an object and gets reflected back into the ISL29030A, the reflected IR light is converted into current, as shown by the IR spectral response in Figure 7. One entire proximity measurement takes 0.54ms for one conversion (which includes 0.1ms spent driving the LED), and the period between proximity measurements is decided by PROX_SLP (sleep time) in Register 1 Bits 6:4. Average LED driving current consumption is given by Equation 1. A typical IRDR scheme is 220mA amplitude pulses every 800ms, which yields 28μA DC. Total Current Consumption Total current consumption is the sum of IDD and IIRDR. The IRDR pin sinks current (as shown in Figure 4), and the average IRDR current can be calculated using Equation 1. IDD depends on voltage and the mode of operation, as shown in Figure 11. Interrupt Function The ISL29030A has an intelligent interrupt scheme designed to shift some logic processing away from intensive microcontroller I2C polling routines (which consume power) and toward a more independent light sensor that can instruct a system to “wake up” or “go to sleep.” An ALS interrupt event (ALS_FLAG) is governed by Registers 5 through 7. The user writes high and low threshold values to these registers, and the ISL29030A issues an ALS interrupt flag if the actual counts stored in Registers 0x9 and 0xA are outside the user-programmed window. The user must write 0 to clear the ALS_FLAG. A proximity interrupt event (PROX_FLAG) is governed by the high and low thresholds in Registers 3 and 4 (PROX_LT and PROX_HT). PROX_FLAG is set when the measured proximity data is greater than the high threshold a user-specified consecutive number of times (X; set by the user; see next paragraph). The proximity interrupt flag is cleared when the proximity data is lower than the low proximity threshold X consecutive times, or when the user writes “0” to PROX_FLAG. Interrupt persistency is another useful option available for both ALS and proximity measurements. Persistency requires a user- specified number (X) of consecutive interrupt flags before the INT pin is driven low. Both ALS and Prox have their own independent interrupt persistency options. See ALS_PRST and PROX_PRST bits in Register 2. The final interrupt option is the ability to AND or OR the two interrupt flags using Register 2 Bit 0 (INT_CTRL). If the user wants simultaneous ALS and Prox interrupts to happen before changing the state of the interrupt pin, the user sets this bit high. If the user wants the interrupt pin to change state when either the ALS or the Proximity interrupt flag goes high, the user leaves this bit at its default value of 0. Analog-Out IALS Pin When ALS_EN = 1, the analog IALS output pin sources a current directly proportional to the digital count stored in register bits ALSIRDATA[11:0]. When ALS_EN = 0, this pin is in a high impedance state. See Figure 15 for the effects of the compliance voltage (VI_ALS) on IALS. ALS Range 1 Considerations When measuring ALS counts higher than 1800 on range 1 (ALSIR_MODE = 0, ALS_RANGE = 0, ALS_DATA > 1800), the user must switch to range 2 (change the ALS_RANGE bit from 0 to 1) and re-measure ALS counts. This recommendation pertains only to applications where the light incident upon the sensor is IR-heavy and is distorted by tinted glass that increases the ratio of infrared to visible light. For more information, contact the factory. VDD Power-up and Power Supply Considerations At power-up, ensure a VDD slew rate of 0.5V/ms or greater. After power-up, or if the power supply temporarily deviates from the factory specification (2.25V to 3.63V), Intersil recommends the user write the following: 0x00 to register 0x01, 0x29 to register 0x0F, 0x00 to register 0x0E, and 0x00 to register 0x0F. The user should then wait ~1ms or more and then rewrite all registers to the desired values. If the user prefers a hardware reset method instead of writing to test registers, then set VDD =0V for 1 second or more, power up again at the required slew rate, and write the desired values to the registers. Power-Down The user can set power-down in two ways. The first is to set both PROX_EN and ALS_EN bits to 0 in Register 1. The second and more simple way is to set all bits in Register 1 to 0 (0x00). Calculating Lux When in ALS mode, the ISL29030A ADC output codes are directly proportional to lux (see ALSIR_MODE bit). In Equation 2, Ecalc is the calculated lux reading, and OUT represents the ADC code. The constant, α, which is to plug in, is determined by the range bit, ALS_RANGE (register 0x1 bit 1) and is independent of the light source type. FIGURE 4. CURRENT DRIVE MODE OPTIONS PIN 8 - IRDR 220mA (PROX_DR = 1) (IRDR IS HI-Z WHEN NOT DRIVING) 110mA (PROX_DR = 0) IlRDR AVG () IlRDR PEAK () 100μs × TSLEEP 540μs + -------------------------------------------------------- = (EQ. 1) Ecalc α RANGE OUTADC × = (EQ. 2) |
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