ISL29018 Datasheet, PDF (8/15 Pages) Intersil Corporation – Digital Ambient Light Sensor and Proximity Sensor with Interrupt Function

ISL29018
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.
TABLE 5. PROXIMITY SENSING SCHEME
BIT 7
OPERATION
0
Sensing IR from LED and ambient
1
Sensing IR from LED with ambient IR rejection
2. Modulation Frequency: Bits 6. This bit sets the IR LED
driver’s modulation frequency.
TABLE 6. MODULATION FREQUENCY
BITS 6
MODULATION FREQUENCY
(kHz)
0
DC
1
360
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.
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
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.
.
TABLE 8. RESOLUTION/WIDTH
BITS 3 TO 2
00
01
10
11
NUMBER OF CLOCK CYCLES
2¹⁶ = 65,536
2¹² = 4,096
2⁸ = 256
2⁴ = 16
n-BIT ADC
16
12
8
4
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 499kΩ R_EXT resistor.
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
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.
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
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.
Test Register (08 hex)
The part functions in normal operation mode when Register
8 is set to 0x00.
Calculating Lux
The ISL29018’s ADC output codes, DATA, are directly
proportional to lux in the ambient light sensing as shown in
Equation 1.
E_cal = α × DATA
(EQ. 1)
Here, E_cal 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
8
FN6619.1
February 11, 2010