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ISL29011 Datasheet(PDF) 8 Page - Intersil Corporation |
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ISL29011 Datasheet(HTML) 8 Page - Intersil Corporation |
8 / 15 page 8 FN6467.2 May 14, 2009 Command Register II 01(hex) The second command register has the following functions: 1. Proximity Sensing Scheme: Bit 7. This bit programs the function of the proximity detection. Logic 0 of this bit, Scheme 0, makes full n (4, 8, 12, 16) bits (unsigned) proximity detection. The range of Scheme 0 proximity count is from 0 to 2n. Logic 1 of this bit, Scheme 1, makes n-1 (3, 7, 11, 15) bits (2’s complementary) proximity_less_ambient detection. The range of Scheme 1 proximity count is from -2(n-1) to 2(n-1). While Scheme 0 has wider dynamic range, Scheme 1 proximity detection is less affected by the ambient IR noise variation. 2. Modulation Frequency: Bits 6. This bit sets the IR LED driver’s modulation frequency. 3. Amplitude of IR driver current: Bits 5 and 4. This device provides current source to drive an external IR LED. The drive capability can be programmed through Bits 5 and 4. For example, the device sources 12.5mA out of the IRDR pin if Bits 5 and 4 are 0. 4. Resolution: Bits 3 and 2. Bits 3 and 2 determine the ADC’s resolution and the number of clock cycles per conversion in Internal Timing Mode. Changing the number of clock cycles does more than just change the resolution of the device. It also changes the integration time, which is the period the device’s analog-to-digital (A/D) converter samples the photodiode current signal for a measurement. . 5. Range: Bits 1 and 0. The Full Scale Range (FSR) can be adjusted via I2C using Bits 1 and 0. Table 9 lists the possible values of FSR for the 499k Ω REXT resistor. Data Registers (02 hex and 03 hex) The device has two 8-bit read-only registers to hold the data from LSB to MSB for ADC. The most significant bit (MSB) is accessed at 03 hex, and the least significant bit (LSB) is accessed at 02 hex. For 16-bit resolution, the data is from D0 to D15; for 12-bit resolution, the data is from D0 to D11; for 8-bit resolution, the data is from D0 to D7. The registers are refreshed after every conversion cycle. Interrupt Registers (04, 05, 06 and 07 hex) Registers 04 and 05 hex set the low (LO) threshold for the interrupt pin and the interrupt flag. 04 hex is the LSB and 05 hex is the MSB. By default, the Interrupt threshold LO is 00 hex for both LSB and MSB. Registers 06 and 07 hex set the high (HI) threshold for the interrupt pin and the interrupt flag. 06 hex is the LSB and 07 hex is the MSB. By default, the Interrupt threshold HI is FF hex for both LSB and MSB. Calculating Lux The ISL29011’s ADC output codes, DATA, are directly proportional to lux in the ambient light sensing. Here, Ecal is the calculated lux reading. The constant α is determined by the Full Scale Range and the ADC’s maximum output counts. The constant is independent on the light sources (fluorescent, incandescent and sunlight) because of the light sources’ IR component is removed during the light signal process. The constant can also be viewed as the sensitivity: the smallest lux measurement the device can measure as shown in Equation 2. Here, Range(k) is defined in Table 9. Countmax is the maximum output counts from the ADC. TABLE 5. PROXIMITY SENSING SCHEME BIT 7 OPERATION 0 Sensing IR from LED and ambient 1 Sensing IR from LED with ambient IR rejection TABLE 6. MODULATION FREQUENCY BITS 6 MODULATION FREQUENCY (kHz) 0DC 1 360 TABLE 7. CURRENT SOURCE CAPABILITY AT IRDR PIN BITS 5 TO 4 IRDR PIN SOURCE CURRENT 00 12.5mA IR LED driver 01 25mA IR LED driver 10 50mA IR LED driver 11 100mA IR LED driver TABLE 8. RESOLUTION/WIDTH BITS 3 TO 2 NUMBER OF CLOCK CYCLES n-BIT ADC 00 216 = 65,536 16 01 212 = 4,096 12 10 28 = 256 8 11 24 = 16 4 TABLE 9. RANGE/FSR LUX BITS 1:0 k RANGE(k) FSR (LUX) @ ALS SENSING FSR @ IR SENSING 00 1 Range1 1,000 Refer to page 4 01 2 Range2 4,000 Refer to page 4 10 3 Range3 16,000 Refer to page 4 11 4 Range4 64,000 Refer to page 4 TABLE 10. DATA REGISTERS ADDRESS (hex) CONTENTS 02 D0 is LSB for 4, 8, 12 or 16-bit resolution, D3 is MSB for 4-bit resolution, D7 is MSB for 8-bit resolution 03 D15 is MSB for 16-bit resolution, D11 is MSB for 12-bit resolution Ecal α DATA × = (EQ. 1) α Range k () Countmax ---------------------------- = (EQ. 2) ISL29011 |
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