SI1120-A-GM_技术文档

Si1120

PROXIMITY/AMBIENT LIGHT SENSOR WITH PWM OUTPUT

Features

Pin Assignments

 Typically 50 cm meter proximity  High EMI immunity without

range with single pulse

shielded packaging

Si1120

ODFN

 Seven precision optical

 Power supply: 2.2–3.7 V

measurement modes:

 Operating temperature range:

3 proximity ranges

3 dc ambient ranges

1 calibration mode

–40 to +85 °C

1

2

3

4

8

7

6

5

PRX

VSS

MD

 Typical 10 µA current

TXGD

consumption

TXO

STX

SC

 Low-noise ambient cancelling

circuit allows maximum

sensitivity with 8–12 bit resolution

 Programmable 400/50 mA LED

VDD

constant current driver output

 Allows independent LED supply

 ALS works in direct sunlight

voltage

(100 klux)

U.S. Patent #5,864,591

U.S. Patent #6,198,118

Other patents pending

 Small outline 3 x 3 mm (ODFN)

 Minimum reflectance sensitivity

2

<1 µW/cm

Applications

 Handsets

 Notebooks/PCs

 Touchless switches

 Occupancy sensors

 Consumer electronics

 Industrial automation

 Display backlighting control

 Photo-interrupter

Description

The Si1120 is a low-power, reflectance-based proximity and ambient light

sensor with advanced analog signal processing and analog PWM output.

It includes an integrated differential photodiode, signal processor, and

LED driver. Proximity sensing is based on the measurement of reflected

light from an external, optically-isolated, strobed LED. A separate visible

light photodiode is used for ambient light sensing. The standard package

for the Si1120 is an 8-pin ODFN.

Rev. 1.0 8/10

Si1120

Functional Block Diagram

Ambient Light

Sources

Transparent

window

Transparent

window

MUX

AMP

CMP

PWM

Output

PRX

VDD

Infrared

BUF

emitter

IR

VIS

Product

Case

RAMP

GEN

VREG

STX

SC

TXO

Optical Block

MODE

CTRL

TX

MD

VSS

TXGD

3.3 V

P0.0/VREF

VDD / DC+

GND / DC-

C1

1.0 uF

Si1120

P0.1 / AGND

P0.2 / XTAL1

P0.3 / XTAL2

P0.4 / TX

VSS

MD

PRX

TXGD

P0.5 / RX

P0.6 / CNVSTR

P0.7 / IREF0

SC

TXO

STX

VDD

P1.0

C8051F931

P1.1

P1.2

P1.3

P1.4

P1.5

P1.6

DCEN

VBAT

R1

30 ohm

TX LED

C2

10 uF

C3

0.1 uF

XTAL3

XTAL4

C4

68.0 uF

GND

RST / C2CK

P2.7 / C2D

Figure 1. Si1120 Typical Application Example of Digital Proximity and Ambient Light Sensor with

C8051F931 MCU and I²C Interface

2

Rev. 1.0

Si1120

TABLE OF CONTENTS

Section

Page

1. Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

2. Application Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

2.1. Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

2.2. Mode Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

2.3. Proximity Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

2.4. Ambient-Light Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

2.5. Choice of LED and LED Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

2.6. Power-Supply Transients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

2.7. Practical Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

3. Pin Descriptions—Si1120 (ODFN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

4. Ordering Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

5. Photodiode Centers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

6. Package Outline (8-Pin ODFN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

Document Change List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

Rev. 1.0

3

Si1120

1. Electrical Specifications

Table 1. Absolute Maximum Ratings*

Parameter

Conditions

Min

–0.3

–40

–65

–0.3

Typ

—

Max

5.5

85

Units

V

Supply Voltage

Operating Temperature

Storage Temperature

—

°C

V

—

85

Voltage on TXO with respect to

GND

—

5.5

Voltage on all other Pins with

respect to GND

–0.3

—

VDD + 0.3

V

Maximum Total Current through

TXO (TXO active)

500

600

100

2

mA

kV

Maximum Total Current through

TXGD and VSS

—

Maximum Total Current through

all other Pins

—

ESD Rating

Human body model

—

*Note: Stresses above those listed in this table may cause permanent damage to the device. This is a stress rating only, and

functional operation of the devices at those or any other conditions above those indicated in the operational listings of

this specification is not implied. Exposure to maximum rating conditions for extended periods may affect device

reliability.

Table 2. Recommended Operating Conditions

Parameter

Symbol

Conditions / Notes

Min

Typ Max

Units

Typical Operating Conditions (T = 25 °C)

A

Supply Voltage

V

T = –40 to +85 °C,

2.2

3.3

3.7

V

DD

V

to GND, TXGD

DD

Operating Temperature

–40

25

—

85

—

°C

V

SC/MD/STX High Threshold

SC/MD/STX Low Threshold

VIH

VIL

V

–0.7

DD

—

0.6

1.0

100

250

950

V

1

Active TXO Voltage

—

V

ALS Operating Range

Edc

—

kLx

Hz

nm

2

Proximity Conversion Frequency

—

125

850

3

LED Emission Wavelength

600

Notes:

1. Minimum R1 resistance should be calculated based on LED forward voltage, maximum LED current, LED voltage rail

used, and maximum active TXO voltage.

2. When in Mode 0 and operating at 250 Hz, STX pulse width should be limited to 1 ms.

3. When using LEDs near the min and max wavelength limits, higher radiant intensities may be needed to achieve the end

system's proximity sensing performance goals.

4

Rev. 1.0

Si1120

Table 3. Electrical Characteristics

Parameter

Symbol

Conditions / Notes

Min

Typ Max

Units

IDD Shutdown

SC >VIH, VDD = 2.7 to 3.7,

T = 27 °C

—

0.1

1.0

µA

IDD Current Idle

SC = STX <VIL

—

90

14

150

—

µA

IDD Current During Transmit,

Not Saturated

V

= 3.3 V, LED I = 400 mA

mA

DD

IDD Current During Transmit,

Not Saturated

V

= 3.3 V, LED I = 50 mA

—

3

—

mA

DD

PRX Pulse Width Range

PRX Logic High Level

Tprx

VOH

VOL

Emin

V

= 3.3 V

0.5

—

2500

—

us

V

DD

I

= –4 mA

= 4 mA

V

–0.7

DD

OH

PRX Logic Low Level

I

—

0.6

—

V

OL

2

Min. Detectable Reflectance Input

V

= 3.3 V (Mode 0,2)

1

µW/cm

mW/cm

us

DD

2

Max. Detectable Reflectance Input Emax1

Max. Detectable Reflectance Input Emax2

V

= 2.2 V (Mode 3)

= 3.7 V (Mode 3)

= 3.3 V, Mode 1

12

48

7

—

DD

V

—

Tpwcal

Itxo_sd

Itxo

V

—

Calibration Mode PRX Pulse Width

TXO Leakage Current

DD

V

= 3.3 V, No strobe

0.01

400

1

µA

DD

TXO Current (TX High Power)

V

= 3.3 V,

—

mA

DD

TXO = 1 V (Mode 0)

TXO Current (TX Low Power)

Itxo

V

= 3.3 V,

—

50

—

mA

DD

TXO = 1 V (Mode 2,3)

Power Up Latency*

V

= 3.3 V

—

500

100

10

535

—

µs

Lx

DD

Full-Scale Ambient Light

FSals1

FSals2

FSals3

V

= 3.3 V, Mode 5

= 3.3 V, Mode 6

= 3.3 V, Mode 7

DD

—

kLx

—

*Note: Refer to "2.2. Mode Selection" on page 7 for additional information.

Rev. 1.0

5

Si1120

2. Application Information

2.1. Theory of Operation

The Si1120 is an active optical-reflectance proximity detector and ambient-light sensor with a pulse-width

modulated output. Depending on the mode selected, the duration of the PRX active (low) state is proportional to

the amount of reflected light, the amount of zero-reflectance offset, or the amount of ambient light. The detection

rate can be set by adjusting the frequency of the STX signal.

The dual-port, active reflection proximity detector has significant advantages over single-port, motion-based

infrared systems, which are good only for triggered events. Motion detection only identifies proximate moving

objects and is ambiguous about stationary objects. The Si1120 allows in- or out-of-proximity detection, reliably

determining if an object has left the proximity field or is still in the field even when it is not moving.

An example of a proximity detection application is controlling the display and speaker of a cellular telephone. In this

type of application, the cell phone turns off the power-consuming display and disables the loudspeaker when the

device is next to the ear, then reenables the display (and, optionally, the loudspeaker) when the phone moves more

than a few inches away from the ear.

For small objects, the drop in reflectance is as much as the fourth power of the distance; this means that there is

less range ambiguity than with passive motion-based devices. For example, a sixteen-fold change in an object's

reflectance means only a fifty-percent drop in detection range. The Si1120 periodically measures proximity at a rate

that can be set by an external controller.

The Si1120 modes are:

 PRX400

 PRX50

 PRX50H

 OFC

Proximity, 400 mA LED current

Proximity, 50 mA LED current

Proximity, 50 mA LED current, high reflectance range

Offset calibration (proximity mode, no LED current)

Visible ambient (10 klux sunlight)

 VAMB

 VIRL

Visible and infrared ambient light, low range (500 lux sunlight)

Visible and infrared ambient light, high range (128 klux sunlight)

 VIRH

6

Rev. 1.0

Si1120

2.2. Mode Selection

The Si1120 features a shutdown mode, three proximity-detection modes, three ambient-light sensing modes, and

an offset calibration for high-sensitivity mode. Mode selection is accomplished through the sequencing of the SC

(shutdown/clock), MD (mode), and STX (strobe/transmit) pins.

The part enters shutdown mode unconditionally when SC is high. Each of the MD and STX inputs should be set to

a valid high or low state. In shutdown mode, the PRX output is tri-stated, and the power-supply and TXO output

leakage currents are negligible.

The active modes are set by clocking the state of MD and STX on the falling edge of SC and then setting MD to the

required state. Since setting SC high forces shutdown, SC must be held low for the selected mode to remain

active. The timing diagram in Figure 2 illustrates the programming sequence. Table 4 indicates the various mode

encodings. After the correct state has been programmed, the STX input is used to trigger measurements.

Figure 2. Si1120 Mode Programming Timing Diagram

Table 4. Mode Control Table

Mode

PRX400

OFC

Description

STX (Latch) MD (Latch) MD (Static)

Proximity, 400 mA LED current (Mode 0)

Offset calibration for high sensitivity (Mode 1)

Proximity, 50 mA LED current (Mode 2)

Proximity, 50 mA LED current, high reflectance (Mode 3)

Visible and infrared ambient, low range (Mode 4)

Visible ambient (Mode 5)

0

1

0

1

0

1

0

1

0

1

0

1

0

1

PRX50

PRX50H

VIRL

VAMB

VIRH

Visible and infrared ambient, high range (Mode 6)

(Reserved) Reserved mode

If the mode must be changed, the SC pin may need to be rearmed (set high), in which case the shutdown mode is

set and a power-on latency of about 500 µs is incurred upon enabling of the selected mode when SC goes back

low. Following a mode change, STX must be kept low during the power-up latency period. If the host sets STX too

early, the Si1120 may not begin a measurement cycle; PRX does not assert. If this occurs, the host can restart a

measurement by toggling STX.

Rev. 1.0

7

Si1120

2.3. Proximity Modes

In proximity mode, an LED sends light pulses that are reflected from the target to a photodiode and processed by

the Si1120’s analog circuitry. Light reflected from a proximate object is detected by the receiver, and the Si1120

converts the light signal into a pulse at the PRX output of a duration proportional to the amount of reflected light.

The LED is turned off at the trailing (rising) edge of the PRX pulse. The detection cycle may be aborted before the

end of the PRX pulse by bringing STX low. This allows the system designer to limit the maximum LED “on” time in

applications where high reflectivity periods are not of interest, thus saving power and minimizing the LED duty

cycle. Aborting the detection cycle at a set time also enables fast threshold comparison by sampling the state of the

PRX output at the trailing (falling) edge of the STX input. An active (low) PRX output when STX falls means that an

object is within the detection range. Forcing a shorter detection cycle also allows a faster proximity measurement

rate thus allowing more samples to be averaged for an overall increase in the signal-to-noise ratio.

For long-range detection, PRX400 mode is selected. For short-range detection, PRX50 mode is selected. PRX50H

mode is typically used in short-range, single-optical-port applications where the internal optical reflection level is

high. The greater reflectance range combined with a lower LED power prevents internal reflections from saturating

the receiver circuit.

The offset calibration mode works the same way as the other proximity modes but without turning on the LED. This

allows precise measurement of the environment and Si1120 internal offsets without any LED light being reflected.

The offset calibration mode also allows compensation of drifts due to supply and temperature changes.

Figure 3. Proximity Mode Timing Diagram

Figure 4. Proximity Mode Timing Diagram (Aborted Cycle)

8

Rev. 1.0

Si1120

40

35

30

25

20

15

10

5

47%, Hand, 1 Lux

47%, Hand, 300 Lux Fluorescent

47%, Hand, 300 Lux Incandescent

18% Gray Card, 1 Lux

92% White Card, 1 Lux

0

200

400

600

800

1000

1200

1400

1600

1800

2000

PRX Pulse Width (us)

Figure 5. PRX400 Mode 0

25

47%, Hand, 1 Lux

20

15

10

5

47%, Hand, 300 Lux Fluorescent

47%, Hand, 300 Lux Incandescent

18% Gray Card, 1 Lux

92% White Card, 1 Lux

0

50

100

150

PRX Pulse Width (us)

200

250

300

Figure 6. PRX50 Mode 2

Rev. 1.0

9

Si1120

40

35

30

25

20

15

10

5

18% Gray Card, 400 mA

18% Gray Card, 50 mA

92% White, 400 mA

92% White, 50 mA

0

200

400

600

800

1000

1200

1400

1600

1800

2000

PRX Pulse Width (us)

Figure 7. Combined PRX400 and PRX50

10

Rev. 1.0

Si1120

2.4. Ambient-Light Modes

Proximity offset and gain can be affected a few percent by high ambient light levels (e.g. sunlight or strong

incandescent lighting). While the cal mode can be used to determine offsets from large ambient light or ambient

noise levels in PRX400 and PRX50 modes, direct measurement of the ambient levels can help identify whether

changes in reflectance are valid or in fact due to large ambient light changes. Usually, this is only an issue in high

reflectance situations, such as single window operation without good optical isolation, where large changing

ambients are an issue.

The Si1120 has two photodiodes, each of which peaks at a different wavelength. The VAMB mode uses the visible

light photodiode which peaks at around 530 nm. On the other hand, the VIRH and VIRL modes use the photodiode

which peaks at around 830 nm. Although the visible-light photodiode peaks near 550 nm (considered the peak

wavelength of human perception), the Si1120 visible photodiode extends to infrared light as well. Similarly, the

Si1120 infrared photodiode detects infrared light as well as part of the visible light spectrum. The Si1120 treats

ultraviolet, visible, and infrared light as a continuous spectrum.

The ratio between the visible and infrared photodiode readings provides a good clue to the type of light source. The

reason is that each light source consists of a characteristic mix of infrared and visible light. For example, blackbody

radiators, such as incandescent or halogen lamps, can have significant energy in the infrared spectrum. On the

other hand, fluorescent lamps have more energy in the visible light spectrum. The term “color ratio” will be used to

describe the relative strength of the visible photodiode reading relative to the infrared photodiode reading. Human

color vision employs a similar principle.

The VAMB/VIRH or VAMB/VIRL color ratios are representative of the Si1120's color perception. Choosing between

these two color ratios depends on the light intensity. In general, VAMB/VIRL should be used first since VIRL has

higher sensitivity. For higher light intensities, the VAMB/VIRH ratio should be used.

Note that VAMB, VIRH, and VIRL pulse widths are used as dividends and divisors in these ratios. What this means

is that the pulse width offsets (at 0 lux) need to be removed prior to usage in the above color ratios. For best

precision, it is best to take VAMB, VIRH, and VIRL measurements at 0 lux and to use actual measured values.

However, a good rule of thumb is to subtract 7.1 µs, 11.3 µs, and 9.9 µs respectively from VAMB, VIRH, and VIRL

(then assigning 0 µs to any resulting negative value). This rule-of-thumb can be used when accuracy is less critical.

Unless stated otherwise, the plots and figures used in this data sheet use offset-corrected values for VAMB, VIRH,

and VIRL.

Once a color ratio has been derived, the light type(s) and lux ratios are also identified. The lux ratio describes the

ratio between the desired lux value and VAMB, VIRL, or VIRH (depending on the situation). The appropriate lux

ratio, when multiplied with the applicable measurement, yields the final calculated lux value. Without any

calibration, it should be possible to arrive within 50% (or 50 lux) of the absolute lux value.

Figure 8. Ambient Light Mode Timing Diagram

Rev. 1.0

11

Si1120

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

4000

3500

3000

2500

2000

1500

1000

500

VAMB

VIRL

0

400

800

1200

1600

2000

W6H7ꢀQyrꢀXvquꢀꢀꢁW6H7ꢀꢄꢀWDSCꢀ8yꢅꢀShvꢀ!#ꢇ

400

500

600

700

800

900

1000

Wavelength (nm)

Figure 12. Incandescent/Halogen Transfer

Function

Figure 9. Si1120 Typical Spectral Response

100

80

60

40

20

0

2500

2000

1500

1000

500

0

100

200

300

400

500

600

700

0

50

100

150

200

250

300

350

400

450

500

VIRH Pulse Width (VIRL, VAMB saturated)

W6H7ꢀQyrꢀXvquꢀꢁW6H7ꢄWDSGꢀ8yꢅꢀShvꢀ3ꢂꢆ!ꢇ

Figure 10. Sunlight Transfer Function

Figure 13. CFL Transfer Function

140

4

3.5

3

120

100

80

60

40

20

0

2.5

2

1.5

1

0.5

0

10

15

20

25

30

35

40

0

200

400

600

800

1000

1200

1400

W6H7ꢀꢄꢀWDSCꢀ8yꢅꢀShv

WDSGꢀQyrꢀXvquꢀꢁWDSGꢀ1ꢀ &ꢂꢂꢃꢀW6H7ꢀꢄꢀWDSGꢀ8yꢅꢀShvꢀꢆꢂ'ꢇ

Figure 14. Lux/VAMB vs. Color Ratio

Figure 11. Low Light Transfer Function

12

Rev. 1.0

Si1120

0.2

0.16

0.12

0.08

0.04

0

0.04

0.05

0.06

0.07

0.08

0.09

0.1

W6H7ꢀꢄꢀWDSGꢀ8yꢅꢀShv

Figure 15. Lux/VIRL Ratio vs. Color Ratio

Rev. 1.0

13

Si1120

2.5. Choice of LED and LED Current

In order to maximize detection distance, the use of an infrared LED is recommended. However, red (visible) LEDs

are viable in applications where a visible flashing LED may be useful and a shorter detection range is acceptable.

Red LEDs do not permit the use of infrared filters and thus are more susceptible to ambient-light noise. This added

susceptibility effectively reduces the detection range. White LEDs have slow response and do not match the

Si1120’s spectral response well; they are, therefore, not recommended.

The Si1120 maintains excellent sensitivity in high ambient and optically noisy environments, most notably from

fluorescent lights. In very noisy environments, the maximum sensitivity may drop by a factor of up to one hundred,

causing a significant reduction in proximity range. With reduced sensitivity, the effect of optical environmental noise

is reduced. For this reason, it is best to drive the LED with the maximum amount of current available, and an

efficient LED should be selected. With careful system design, the duty cycle can be made very low, thus enabling

most LEDs to handle the peak current of 400 mA while keeping the LED’s average current draw on the order of a

few microamperes. Total current consumption can be kept well below that of a typical lithium battery's self-

discharge current of 10 µA, thus ensuring the battery's typical life of 10 years.

Another consideration when choosing an LED is the LED's half-angle. An LED with a narrow half-angle focuses the

available infrared light using a narrower beam. When the concentrated infrared light encounters an object, the

reflection is much brighter. Detection of human-size objects one meter away can be achieved when choosing an

LED with a narrower half-angle and coupling it with an infrared filter on the enclosure.

2.6. Power-Supply Transients

2.6.1. V Supply

DD

The Si1120 has good immunity from power-supply ripple, which should be kept below 50 mVpp for optimum

performance. Power-supply transients (at the given amplitude, frequency, and phase) can cause either spurious

detections or a reduction in sensitivity if they occur at any time within the 300 µs prior to the LED being turned on.

Supply transients occurring after the LED has been turned off have no effect since the proximity state is latched

until the next cycle. The Si1120 itself produces sharp current transients, and, for this reason, must also have a bulk

capacitor on its supply pins. Current transients at the Si1120 supply can be up to 20 mA.

2.6.2. LED Supply

If the LED is powered directly from a battery or limited-current source, it is desirable to minimize the load peak

current by adding a resistor in series with the LED’s supply capacitor. If a regulated supply is available, the Si1120

should be connected to the regulator’s output and the LED to the unregulated voltage, provided it is less than 6 V.

There is no power-sequencing requirement between VDD and the LED supply. The typical LED current peak of

400 mA can induce supply transients well over 50 mVpp, but those transients are easy to decouple with a simple

R-C filter because the duty-cycle-averaged LED current is quite low.

2.6.3. LED Supply (Single Port Configuration)

When using a single optical port, the Si1120 attempts to detect changes in reflection that can be less than one

percent of the received signal. A constant LED current is essential to avoid spurious detections. It is, therefore,

critical to prevent TXO saturation. If TXO is allowed to saturate in a single-port configuration, the Si1120 will be

very sensitive to LED power-supply variations and even to frequency variations at the STX input. A reservoir

capacitor should be chosen based on the expected TXO pulse width, and a series resistor should be selected

based on the STX duty cycle.

2.6.4. LED Supply (Dual Port Configuration)

When using separate optical ports for the LED and for the Si1120, the signal reflected from the target is large

compared with the internal reflection. This eliminates the need for keeping the LED current constant, and the TXO

output can, therefore, be allowed to saturate without problem. In addition, only the first 10 µs of the LED turn-on

time are critical to the detection range. This further reduces the need for large reservoir capacitors for the LED

supply. In most applications, a 10 µF capacitor is adequate. A 100  to 1 k resistor should be added in series to

minimize peak load current.

14

Rev. 1.0

Si1120

2.7. Practical Considerations

It is important to have an optical barrier between the LED and the Si1120. The reflection from objects to be

detected can be very weak since, for small objects within the LED's emission angle, the amplitude of the reflected

signal decreases in proportion with the fourth power of the distance. The receiver can detect a signal with an

2

irradiance of 1 µW/cm . An efficient LED typically can drive to a radiant intensity of 100 mW/sr. Hypothetically, if

2

this LED were to couple its light directly into the receiver, the receiver would be unable to detect any 1 µW/cm

2

signal since the 100 mW/cm leakage would saturate the receiver. Therefore, to detect the 1 µW/cm signal, the

internal optical coupling (e.g. internal reflection) from the LED to the receiver must be minimized to the same order

of magnitude (decrease by 10 ) as the signal the receiver is attempting to detect. As it is also possible for some

5

LEDs to drive a radiant intensity of 400 mW/sr, it is good practice to optically decouple the LED from the source by

6

a factor of 10 . A Dual-Port Optical Window shown in Figure 16 can accomplish this easily.

If an existing enclosure is being reused and does not have dedicated openings for the LED and the Si1120, the

proximity detector may still work if the optical loss factor through improvised windows (e.g. nearby microphone or

fan holes) or semi-opaque material is not more than 90% in each direction. In addition, the internal reflection from

an encased device's PMMA (acrylic glass) window (common in cellular telephones, PDAs, etc.) must be reduced

through careful component placement. To reduce the optical coupling from the LED to the Si1120 receiver, the

distance between the LED and the Si1120 should be maximized, and the distance between both components (LED

and Si1120) to the PMMA window should be minimized. The PRX50H mode can be used for the Single-Port

Optical Window shown in Figure 16.

Another practical consideration is that system optical leakage, overlay thickness and transmittance, LED efficiency

variation, TXO sink drive and photodiode part-to-part difference all collectively lead to reflectance measurement

variation even under a given proximity condition. For applications requiring PRX pulse width consistency across

multiple systems, factory calibration is recommended. Factory calibration involves taking a reference measurement

against a consistent and reproducible reflective object (such as an 18% gray card) at a fixed distance during

system production testing. Having this reference proximity measurement stored in non-volatile RAM or Flash

allows host software to make necessary adjustments to incoming PRX pulse widths against this reference

proximity measurement. A low background infrared environment is recommended.

For best proximity range performance, the system optical leakage can be characterized during factory calibration.

To do this, a reference proximity measurement is made when it is known that no object is in proximity of the system

at the time of the measurement. The 'no object' reference measurement allows host software to establish the level

of system optical leakage and make the necessary corrections to account for this.

In a similar way, for applications with heavy reliance on ALS accuracy, measurements using reference light sources

during factory calibration can be used to make adjustments to VAMB, VIRL, and VIRH measurements.

Transparent

window

PRX50H Mode

Si1120

Internal Reflection Optical block

Transmit LED

Optical block

Single-port Optical Window

Dual-port Optical Window

Figure 16. Dual-Port and Single-Port Optical Window

Rev. 1.0

15

Si1120

3. Pin Descriptions—Si1120 (ODFN)

PRX

TXGD

TXO

1

2

3

4

8

7

6

5

VSS

MD

SC

STX

VDD

Figure 17. Pin Configurations

Table 5. Pin Descriptions

Description

Name

1

PRX PWM Output.

Outputs a low-going PWM pulse proportional to signal.

TXGD TXGD.

Power ground (LED and PRX driver ground return). Must be connected to VSS.

TXO Transmit Output.

2

3

Normally connected to an infrared LED cathode. The output current is a programmable con-

stant current sink. This output can be allowed to saturate, and output current can be limited by

the addition of a resistor in series with the LED.

4

STX Strobe.

Initiates PS or ALS measurement. Also used as data input for the M2 internal mode control

flip-flop.

5

6

V

Power Supply.

2.2 to 3.7 V voltage source.

DD

SC

Shutdown/Clock.

When high, shuts down the part. When enabling the part, the low-going edge clocks the states

of STX and MD into mode-control D flip-flops M2 and M3.

7

8

MD

Mode Control.

Controls two mode control bits, one directly and the other indirectly, by providing the data input

for the M3 internal mode control flip-flop.

VSS VSS.

Ground (analog ground). Must be connected to TXGD.

16

Rev. 1.0

Si1120

4. Ordering Guide

Part Ordering #

Temperature

Package

Si1120-A-GM

–40 to +85 °C

3x3 mm ODFN8

5. Photodiode Centers

Rev. 1.0

17

Si1120

6. Package Outline (8-Pin ODFN)

Figure 18 illustrates the package details for the Si1120 ODFN package. Table 6 lists the values for the dimensions

shown in the illustration.

Figure 18. ODFN Package Diagram Dimensions

Table 6. Package Diagram Dimensions

Dimension

Min

Nom

Max

A

0.55

0.65

0.75

b

D

0.25

1.40

0.30

3.00 BSC.

1.50

0.35

1.60

D2

e

0.65 BSC.

3.00 BSC.

2.30

E

E2

2.20

0.30

2.40

0.40

L

0.35

aaa

bbb

ccc

ddd

Notes:

0.10

0.08

0.10

1. All dimensions shown are in millimeters (mm).

2. Dimensioning and Tolerancing per ANSI Y14.5M-1994.

18

Rev. 1.0

Si1120

DOCUMENT CHANGE LIST

Revision 0.41 to Revision 0.42

 Removed custom package option.

 Updated Table 1 on page 4.

Added Operating, Storage temps, and ESD to Table 1.

 Updated "4. Ordering Guide" on page 17.

Added ordering part number information.

 Added "6. Package Outline (8-Pin ODFN)" on page

18.

 Updated " Functional Block Diagram" on page 2.

 Added Figures 5, 6, and 7.

 Updated "2.4. Ambient-Light Modes" on page 11.

 Added Figures 9, 10, 11,12, 13, 14, and 15.

 Updated "2.5. Choice of LED and LED Current" on

page 14.

Revision 0.42 to Revision 0.43

 Updated Table 3 on page 5.

Updated power up latency maximum value from 300 to

500 µs.

Updated FSals2 typical value from 128 to 100.

 Updated "2.2. Mode Selection" on page 7.

Revision 0.43 to Revision 1.0

 Updated Table 3 on page 5.

Widened limits of PRX Pulse Width Range

from 4 min / 2200 max to 0.5 min / 2500 max.

PRX Logic High Level changed to VDD – 0.7 from

VDD – 0.5.

Removed IDD current specification for saturated driver

condition.

Removed Temperature Coefficient specification.

Increased power-up latency from 500 to 535 µs.

Changed IDD Current Idle from 120 µA TYP to 90 µA

TYP and 300 µA Max to 150 µA Max.

 Updated first paragraph in "2.4. Ambient-Light

Modes" on page 11.

 Renamed Section “2.7. Mechanical and Optical

Implementation” to “2.7. Practical Considerations” .

Added factory calibration guidance.

 Added "5. Photodiode Centers" on page 17.

Rev. 1.0

19

Si1120

CONTACT INFORMATION

Silicon Laboratories Inc.

400 West Cesar Chavez

Austin, TX 78701

Tel: 1+(512) 416-8500

Fax: 1+(512) 416-9669

Toll Free: 1+(877) 444-3032

Please visit the Silicon Labs Technical Support web page:

https://www.silabs.com/support/pages/contacttechnicalsupport.aspx

and register to submit a technical support request.

The information in this document is believed to be accurate in all respects at the time of publication but is subject to change without notice.

Silicon Laboratories assumes no responsibility for errors and omissions, and disclaims responsibility for any consequences resulting from

the use of information included herein. Additionally, Silicon Laboratories assumes no responsibility for the functioning of undescribed features

or parameters. Silicon Laboratories reserves the right to make changes without further notice. Silicon Laboratories makes no warranty, rep-

resentation or guarantee regarding the suitability of its products for any particular purpose, nor does Silicon Laboratories assume any liability

arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation conse-

quential or incidental damages. Silicon Laboratories products are not designed, intended, or authorized for use in applications intended to

support or sustain life, or for any other application in which the failure of the Silicon Laboratories product could create a situation where per-

sonal injury or death may occur. Should Buyer purchase or use Silicon Laboratories products for any such unintended or unauthorized ap-

plication, Buyer shall indemnify and hold Silicon Laboratories harmless against all claims and damages.

Silicon Laboratories and Silicon Labs are trademarks of Silicon Laboratories Inc.

Other products or brandnames mentioned herein are trademarks or registered trademarks of their respective holders.

20

Rev. 1.0


型号：	SI1120-A-GM
厂家：	SILICON
描述：	PROXIMITY/AMBIENT LIGHT SENSOR WITH PWM OUTPUT 带有PWM输出接近检测/环境光传感器传感器输出元件
文件：	总20页 (文件大小：187K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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