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PDF SFH7770E6 Data sheet ( Hoja de datos )
| Número de pieza | SFH7770E6 | |
| Descripción | Ambient Light and Proximity Sensor | |
| Fabricantes | OSRAM | |
| Logotipo |  |
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SFH 7770 E6
Ambient Light and Proximity Sensor
1 Abstract
This application note describes technical
details and provides some application
guidelines for the combined ambient light
and proximity sensor SFH 7770 E6.
Compared to its predecessors (SFH 7770
E4 and E5), the SFH 7770 E6 features a
mores sensitive proximity sensor (up to
five times improved sensitivity) and
improved ambient light sensor (sensitive
down to 0.03 lx).
The document starts with a general
introduction to the device, followed by a brief
overview on the features (Sec. 2) and
operating modes (Sec. 3) of the sensor. The
integration and operation of the sensor in an
I²C bus environment is described in Sec. 4,
whereas Sec. 5 covers the interrupt
capabilities of the SFH 7770 E6.
Sec. 6 provides a functional description of
the sensor. Optical design guidelines and
application relevant information are given in
Sec. 7 followed by the guidelines for the
electrical design in Sec. 8. Finally Sec. 9
presents a sample software code.
More general information about ambient
light sensing, technical data and I²C bus are
available in the following documents:
- OSRAM OS general application note
on ambient light sensing [1]
- SFH 7770 E6 datasheet [2]
- I²C bus specification [3]
- Driving a LED with an external driver
(> 200 mA) application note [4]
2 Introduction
The SFH 7770 E6 is a compact device
which is designed for simultaneous
Fig. 1: Ambient Light and Proximity
Sensor SFH 7770 E6.
detection of ambient light and proximity of
reflecting objects. Applications are mobile
phones, PDAs, notebooks, cameras and
other consumer products.
The device includes the following features:
• Proximity Sensor (PS)
- Detection-range up to 200 mm
- Gesture recognition possible
- Outputs to drive up to three IR
emitters
- Optimized for 850 nm emitters
- Immune to ambient light
• Ambient Light Sensor (ALS)
- 0.03lx - 65000lx- High linearity
- Spectral sensitivity well matched to
the human eye
• I2C interface
- 100 kHz / 400 kHz and 3.4 MHz
mode
- 3 programmable measurement
modes (STAND-BY, TRIGGERED,
FREE-RUNNING)
• Current consumption < 5 μA in
STAND-BY mode
• Small package size, 2.8 x 2.8 x 0.9
mm³
February 27, 2012
page 1 of 33
1 page  
Fig. 7: Combined mode structure.
is changing from “1” to “0” during SCL line
stays “1”) followed by the address of the
slave (SFH 7770 E6 address is 0x38). After
the 7bit slave address the read (1) and write
(0) R/W bit of the master will follow. The
R/W bit controls the communication
direction between the master and the
addressed slave. The slave is responding
the proper communication with an
acknowledge command. Acknowledge “A”
(or not acknowledge “NA”) is performed
from the receiver by pulling the SDA line
down (or leave in “1” state).
For the activation of the sensor the master
needs to write an activation command
(0x03) into the corresponding control
register for the ALS (0x80). Each command
needs to be acknowledged by the slave.
After activation the master ends the
communication with a STOP command “P”
(SDA line is changing from LOW to HIGH
during SCL line stays HIGH). In this
example the measurement interval time is
kept at the default value (500 ms).
2. Activation of the PS:
For the activation of the PS sensor the
master needs to write the activation
command (0x03) into the corresponding
control register (0x81). By writing 0x1E into
the I_LED register (0x82) the LED current is
set to 200 mA. The measurement interval is
left at the default value (100 ms). After
activation the master ends the
communication with a STOP command.
3. Wait time:
After activation, the sensor will change from
STAND-BY to FREE-RUNNING mode. After
a delay of 100 ms for ALS / 10 ms for PS
the first measurement value is available and
can be read via the I²C-bus.
4. PS value: reading data
The PS value is accessible via the output
register (0x8F). After reading the 8-bit word,
the communication can be ended by the
master with a not acknowledge “NA” and the
stop command “P”. The PS output reading
of the SFH 7770 E6 can then be converted
from hexadecimal to decimal.
5. ALS value: reading data (LSB and MSB)
The sensor’s 16bit ALS measurement value
is composed of 2 bytes (LSB & MSB). The
bytes are accessible via the two output
registers (0x8C, 0x8D). After addressing the
LSB (least significant byte) resp. the MSB
(most significant byte) output register, the
communication direction has got to be
changed from the slave to the master by
repeating the address and the R/W byte with
a changed R/W bit. After reading LSB and
MSB, the communication is ended by the
master with a not acknowledge “NA” and the
stop condition “P”. The conversion of the
ALS output data of the SFH 7770 E6 from
hexadecimal to decimal can easily be
calculated:
ALS_DATA_LSB = F0 (1111 0000)
ALS_DATA_MSB = 83 (1000 0011)
Final result (hexadecimal): 83 F0 counts
Final result (decimal): 33776 counts, which
correspond to around 30.4 klx (based on a
conversion factor of typ. 0.9 lux/count).
After finishing the measurement, the SFH
7770 E6 mode may be changed to STAND-
BY via the control register.
Combined mode
To ensure interference free communication
the I²C-bus combined mode should be used.
Instead of performing two independent read
or write commands (COM 1 & COM 2) the
commands can be combined by a repeated
February 27, 2012
page 5 of 33
5 Page 
PS_THR LED_3: Threshold level for proximity sensor
RW-Register 0x95
Bit 7 6 5 4 3
data
default
11111111
2
ALS UP_THR LSB: Upper threshold level for ambient light sensor (LSB)
RW-Register 0x96
Bit 7
default
6
5432
LSB data (upper threshold)
11111111
1
1
ALS UP_THR MSB: Upper threshold level for ambient light sensor (MSB)
RW-Register 0x97
Bit 7
default
6
5432
MSB data (upper threshold)
11111111
1
ALS_LO_THR LSB: Lower threshold level for ambient light sensor (LSB)
RW-Register 0x98
Bit 7
default
6
5432
LSB data (upper threshold)
11111111
1
ALS_LO_THR MSB: Lower threshold level for ambient light sensor (MSB)
RW-Register 0x99
Bit 7
default
6
5432
LSB data (upper threshold)
11111111
1
0
0
0
0
0
5 Interrupt Alert
The SFH 7770 E6 provides an interrupt pin,
which can be configured completely by the
user. The register 0x92 allows configuring
the interrupt as active low or active high.
Additionally, the interrupt function can be
configured to operate in latched or normal
mode. In normal mode the interrupt
event/signal is updated after every
measurement, whereas in the latched mode
it is guaranteed that even short peaks are
detected (e.g. the interrupt is held as long as
Interrupt Event Definition
proximity PS data > PS threshold
sensor
ambient
ALS data > ALS upper threshold
light sensor ALS data < ALS lower threshold
Tab. 4: Interrupt event definition.
the microcontroller reads out the interrupt
register).
The interrupt can be set for a PS (PS
threshold) and/or ALS (upper and lower ALS
threshold) event. For the exact interrupt
event definition please refer to Tab. 4. This
is especially valuable as it allows the SFH
7770 E6 to operate as stand alone device in
the free-running mode, independent from
the main microcontroller. This functionality
relieves the microcontroller from active
involvement in the PS / ALS monitoring
resp. measurement cycle and reduces
significantly the I2C-bus traffic, thus reducing
the overall power consumption of the
system. Only if the user-defined thresholds
are violated, the interrupt signal will inform
the microcontroller and the predefined
actions can be executed (e.g. after read-out
of the interrupt and PS / ALS data registers
to get the actual data - if desired).
February 27, 2012
page 11 of 33
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet SFH7770E6.PDF ] | |
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