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FN6619.0

March 3, 2009

brunette hair, as expected and shown in 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

ISL29018 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 ISL29018

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:

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:

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 ISL29018 is relatively insensitive to layout. Like other

even in significantly noisy environments. There are only a

few considerations that will ensure best performance.

sources of noise. Use two power-supply decoupling

capacitor 0.1µF, placed close to the device.

Typical Circuit

A typical application for the ISL29018 is shown in Figure 4.

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.

0.05mA 0.05mA 1mA (50mA∗50%))∗0.4ms

++

+

()

[]/30ms = 0.35mA

(EQ. 9)

0.05mA 0.05mA 1mA (50mA∗50%))∗

++

+

()

[]/100ms = 1.83mA

(EQ. 10)

ISL29018