ISL29011 Datasheet, PDF (10/15 Pages) Intersil Corporation – Digital Ambient Light Sensor and Proximity Sensor with Interrupt Function

ISL29011
Figure 11. Also notice that skin tissue is much more reflective
than hair. IR penetrates into the skin and is reflected or
scattered back from within. As a result, the proximity count
peaks at contact and monotonically decreases as skin moves
away. This characteristic is very different from that of a plain
paper reflector.
Interrupt Function
Depending on the mode of operation set by Bits 7, 6 and 5 of
command register 00 hex, the upper and lower interrupt
thresholds are for either ambient light level or proximity
detection. After each change of mode of operation, it is
expected a new set of thresholds are loaded to interrupt
registers 04, 05, 06 and 07 hex for proper interrupt detection.
Also, the interrupt persist counter will be reset to 0 when the
mode of operation is changed.
LED Modulation for Proximity Detection
ISL29011 offers two ways to modulate the LED in the
Proximity Detection mode - DC or 360kHz (with 50% duty
cycle) by bit 6 of register 01h. At the IRDR pin, there are four
different IRDR LED currents; 12.5, 25, 50, and 100mA
outputs selectable by bits 4 and 5 of register 01h. With the
LED running in the DC mode, the proximity detection is twice
as sensitive but consumes 2 times more current. The
sensitivity of LED 50mA, DC 50mA is identical to that of
100mA, 360kHz modulation. Please note that the ISL29011
does not include a LED.
Current Consumption Estimation
The low power operation is achieved through sequential
readout in the serial fashion, as shown in Figure 3, the
device requires three different phases in serial during the
entire detection cycle to do ambient light sensing, infrared
sensing and proximity sensing. The external IR LED will only
be turned on during the proximity sensing phase under user
program controlled current at modulated frequency depends
on user selections. Figure 3 also shows the current
consumption during each ALS, IR sensing and Proximity
sensing phase. For example, at 8-bit ADC resolution the
integration time is 0.4ms. If user programed 50mA current to
supply external IR LED at 360kHz modulated frequency,
during the entire operation cycle that includes ALS, IR
sensing and Proximity sensing three different serial phases,
the detection occurs once every 30ms, the average current
consumption including external IR LED drive current can be
calculated from Equation 9:
[(0.05mA + 0.05mA + 1mA + (50mA^∗50%))^∗0.4ms)]/30ms = 0.35mA
(EQ. 9)
If at a 12-bit ADC resolution where the integration time for
each serial phase becomes 7ms and the total detection time
becomes 100ms, the average current can be calculated from
Equation 10:
[(0.05mA + 0.05mA + 1mA + (50mA^∗50%))^∗7ms)]/100ms = 1.83mA
(EQ. 10)
Suggested PCB Footprint
It is important that the users check the “Surface Mount
Assembly Guidelines for Optical Dual FlatPack No Lead
(ODFN) Package” before starting ODFN product board
mounting.
http://www.intersil.com/data/tb/TB477.pdf
Layout Considerations
The ISL29011 is relatively insensitive to layout. Like other
I²C devices, it is intended to provide excellent performance
even in significantly noisy environments. There are only a
few considerations that will ensure best performance.
Route the supply and I²C traces as far as possible from all
sources of noise. Use two power-supply decoupling
capacitors 1uF and 0.1µF and place them close to the VDDA
and VDDD pins of the device.
Typical Circuit
A typical application for the ISL29011 is shown in Figure 4.
The ISL29011’s I²C address is internally hardwired as
1000100. The device can be tied onto a system’s I²C bus
together with other I²C compliant devices.
Soldering Considerations
Convection heating is recommended for reflow soldering;
direct-infrared heating is not recommended. The plastic
ODFN package does not require a custom reflow soldering
profile, and is qualified to +260°C. A standard reflow
soldering profile with a +260°C maximum is recommended.
10
FN6467.2
May 14, 2009