S i 11 20
P
ROXIMITY
/ A
MBIENT
L
IGHT
S
ENSOR W I T H
PWM O
UTPUT
Features
Pin Assignments
Typically 50 cm meter proximity
High EMI immunity without
range with single pulse
shielded packaging
Seven precision optical
Power supply: 2.2–3.7 V
measurement modes:
Operating temperature range:
3 proximity ranges
–40 to +85 °C
3 dc ambient ranges
Typical 10 µA current
1 calibration mode
consumption
Low-noise ambient cancelling
Programmable 400/50 mA LED
circuit allows maximum
constant current driver output
sensitivity with 8–12 bit resolution
Allows independent LED supply
ALS works in direct sunlight
voltage
(100 klux)
Small outline 3 x 3 mm (ODFN)
Minimum reflectance sensitivity
<1 µW/cm
2
Si1120
ODFN
PRX
TXGD
TXO
STX
1
2
3
4
8
7
6
5
VSS
MD
SC
VDD
U.S. Patent #5,864,591
U.S. Patent #6,198,118
Other patents pending
Applications
Handsets
Touchless switches
Occupancy sensors
Consumer electronics
Notebooks/PCs
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
Copyright © 2010 by Silicon Laboratories
Si1120
Si1120
Functional Block Diagram
Ambient Light
Sources
Transparent
window
Transparent
window
MUX
AMP
CMP
PRX
BUF
PWM
Output
Infrared
emitter
Product
Case
Optical Block
IR
VIS
RAMP
GEN
STX
SC
MD
VSS
TXGD
MODE
CTRL
TX
VREG
VDD
TXO
3.3 V
VDD / DC+
C1
1.0 uF
GND / DC-
P0.0/VREF
P0.1 / AGND
P0.2 / XTAL1
P0.3 / XTAL2
P0.4 / TX
P0.5 / RX
P0.6 / CNVSTR
P0.7 / IREF0
Si1120
PRX
TXGD
TXO
STX
VSS
MD
SC
VDD
C8051F931
DCEN
VBAT
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
XTAL3
XTAL4
RST / C2CK
P2.7 / C2D
TX LED
C4
68.0 uF
R1
30 ohm
C2
10 uF
C3
0.1 uF
GND
Figure 1. Si1120 Typical Application Example of Digital Proximity and Ambient Light Sensor with
C8051F931 MCU and I
2
C Interface
2
Rev. 1.0
Si1120
T
ABLE O F
C
ONTENTS
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
Supply Voltage
Operating Temperature
Storage Temperature
Voltage on TXO with respect to
GND
Voltage on all other Pins with
respect to GND
Maximum Total Current through
TXO (TXO active)
Maximum Total Current through
TXGD and VSS
Maximum Total Current through
all other Pins
ESD Rating
Human body model
Conditions
Min
–0.3
–40
–65
–0.3
–0.3
—
—
—
—
Typ
—
—
—
—
—
—
—
—
—
Max
5.5
85
85
5.5
VDD + 0.3
500
600
100
2
Units
V
°C
°C
V
V
mA
mA
mA
kV
*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
A
= 25 °C)
Supply Voltage
Operating Temperature
SC/MD/STX High Threshold
SC/MD/STX Low Threshold
Active TXO Voltage
1
ALS Operating Range
Proximity Conversion Frequency
2
LED Emission Wavelength
3
Edc
VIH
VIL
V
DD
T = –40 to +85 °C,
V
DD
to GND, TXGD
2.2
–40
V
DD
–0.7
—
—
—
—
600
3.3
25
—
—
—
—
125
850
3.7
85
—
0.6
1.0
100
250
950
V
°C
V
V
V
kLx
Hz
nm
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
IDD Shutdown
IDD Current Idle
IDD Current During Transmit,
Not Saturated
IDD Current During Transmit,
Not Saturated
PRX Pulse Width Range
PRX Logic High Level
PRX Logic Low Level
Min. Detectable Reflectance Input
Max. Detectable Reflectance Input
Max. Detectable Reflectance Input
Tprx
VOH
VOL
Emin
Emax1
Emax2
Symbol
Conditions / Notes
SC >VIH, VDD = 2.7 to 3.7,
T = 27 °C
SC = STX <VIL
V
DD
= 3.3 V, LED I = 400 mA
V
DD
= 3.3 V, LED I = 50 mA
V
DD
= 3.3 V
I
OH
= –4 mA
I
OL
= 4 mA
V
DD
= 3.3 V (Mode 0,2)
V
DD
= 2.2 V (Mode 3)
V
DD
= 3.7 V (Mode 3)
V
DD
= 3.3 V, Mode 1
V
DD
= 3.3 V, No strobe
V
DD
= 3.3 V,
TXO = 1 V (Mode 0)
V
DD
= 3.3 V,
TXO = 1 V (Mode 2,3)
V
DD
= 3.3 V
FSals1
FSals2
FSals3
V
DD
= 3.3 V, Mode 5
V
DD
= 3.3 V, Mode 6
V
DD
= 3.3 V, Mode 7
Min
—
—
—
—
0.5
V
DD
–0.7
—
—
—
—
—
—
—
—
—
—
—
—
Typ
0.1
90
14
3
—
—
—
1
12
48
7
0.01
400
50
—
500
100
10
Max
1.0
150
—
—
2500
—
0.6
—
—
—
—
1
—
—
535
—
—
—
Units
µA
µA
mA
mA
us
V
V
µW/cm
2
mW/cm
2
mW/cm
2
us
µA
mA
mA
µs
Lx
kLx
kLx
Calibration Mode PRX Pulse Width Tpwcal
TXO Leakage Current
TXO Current (TX High Power)
TXO Current (TX Low Power)
Power Up Latency*
Full-Scale Ambient Light
Full-Scale Ambient Light
Full-Scale Ambient Light
Itxo_sd
Itxo
Itxo
*Note:
Refer to "2.2. Mode Selection" on page 7 for additional information.
Rev. 1.0
5
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