ISL29015 데이터 시트보기 (PDF) - Renesas Electronics

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ISL29015

Integrated Digital Ambient Light Sensor and Proximity Sensor

Renesas Electronics 

ISL29015

ISL29015

Here, EIR is the received IR intensity. The constant  changes

with the spectrum of background IR noise like sunlight and

incandescent light. The also changes with the ADC’s range

and resolution selections.

ADC Output in Proximity Sensing

In the proximity sensing, the ADC output codes, DATA, are

directly proportional to the total IR intensity from the

background IR noise and from the IR LED driven by the

ISL29015.

DATAPROX =   EIR +   ELED

(EQ. 8)

andEIR in Equation 8 have the same meanings as in

Equation 7. The constant  depends on the spectrum of the

used IR LED and the ADC’s range and resolution selections.

ELED is the IR intensity which is emitted from the IR LED and

reflected by a specific objector to the ISL29015. ELED depends

on the current to the IR LED and the surface of the object.

ELED decreases with the square of the distance between the

object and the sensor.

If background IR noise is small, i.e., EIR can be neglected, the

ADC output directly decreases with the distance. If there is

significant background IR noise, the sequence of the proximity

sensing followed by the IR sensing can be implemented. The

differential reading of ADC outputs from the proximity and IR

sensing has no effect of background IR noise and directly

decreases with the distance between the object and the

sensor. Please refer to “Typical Performance Curves” on

page 10 for ADC output vs distance. Figure 9 shows ISL29015

configured at 12-bit ADC resolution, 12.5mA external LED

current at 327.7KHz modulation frequency, detects three

different sensing objects: 92% brightness paper, 18% gray

card and ESD black foam. Figure 10 shows ISL29015

configured at 12-bit ADC resolution, programmed external LED

at 327.7KHz modulation frequency, detects the same sensing

object: 18% gray card under four different external LED

current: 12.5mA, 25mA, 50mA and 100mA to compare the

proximity readout versus distance.

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

327.7kHz 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 ISL29015 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,

1µF and 0.1µF, placed close to the device.

Typical Circuit

A typical application for the ISL29015 is shown in Figure 4. The

ISL29015’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.

FN6522 Rev 0.00

October 31, 2008

Page 8 of 13

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