Si1102

Rev. 1.0

9

For applications where R1 resistance values are small, the proximity range can vary as a function of the ambient IR

condition. A product cover, which limits the visible light intensity, is helpful in reducing this range variation. It is

recommended that the Si1102 be evaluated and tested in-product under the various light conditions it will

encounter under normal product usage. Setting the potentiometer R1 = 0 is not recommended unless the ambient

light condition is known and relatively constant.

At any given R1 threshold setting, there are many factors that determine the precise distance that the Si1102

reports. These factors include object reflectivity, object size, ambient light type and ambient light intensity. When

used in applications where the ambient light is variable, it is recommended the Si1102 optical window be IR

transmissive but visible light opaque.

Figure 3. Proximity Detection Distance vs. R1 (SFH4650 IR LED 850 nm/40 mW)*

*Note: Detection range measured using Kodak Gray cards (18% reflectance), no IR filter under dark ambient conditions (<1 lx).

Table 4. Summary of External Component Values and Operating Conditions

R1

R2

Strobe Frequency

Distance1

IDD Average Current Consumption2

50 k



0

250 Hz

12 to 22 cm

100 µA

50 k



Open

2.0 Hz

12 to 22 cm

5 µA

15 k



0

250 Hz

40 to 50 cm

100 µA

30 k



0

250 Hz

17 to 33 cm

100 µA

Notes:

1. Distance measured with SFH4650 IR LED, with an IR filter, targeting an 18% gray card, 300 lux (Incandescent or CFL)

2. Average current consumption at VDD = 3.3 V, 25 °C and dark ambient conditions (<100 lx).

Detection Distance

5

10

15

20

25

30

35

40

45

50

10

20

30

40

50

60

70

80

90

100

R1(kohm)