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PDF ADPD2211 Data sheet ( Hoja de datos )
| Número de pieza | ADPD2211 | |
| Descripción | High Sensitivity Optical Sensor | |
| Fabricantes | Analog Devices | |
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Data Sheet
Low Noise, High Sensitivity Optical Sensor
ADPD2211
FEATURES
Ultrahigh detectivity photodetector
90 fA/√Hz (typical) ultralow noise floor
Signal-to-noise ratio (SNR) near shot noise limit
137 µA (typical) of supply current when active
(EE = 0 µW/cm2)
1 µA (typical) of supply current in standby
High speed, deep junction photodiode
Nominal linear output current: 240 µA (typical)
Flexible output configuration
Excellent pulse response
High ambient light rejection
Space-saving, 3 mm × 3 mm LFCSP package
APPLICATIONS
Heart rate, pulse oximetry monitoring
(photoplethysmography)
Battery-powered medical sensors
Chemical analysis
FUNCTIONAL BLOCK DIAGRAM
VCC
+
CURRENT
AMPLIFIER
–
ADPD2211
OUT
PWDN GND
Figure 1.
GENERAL DESCRIPTION
The ADPD2211 is an optical sensor optimized for biomedical
applications. Very low power consumption and near theoretical
signal-to-noise ratio (SNR) are achieved by packaging an ultralow
capacitance deep junction silicon photodiode operated in zero
bias photoconductive mode with a low noise current amplifier.
The ADPD2211 offers a typical 400 kHz bandwidth performance,
which is well suited for use with pulsed excitation. The ADPD2211
uses very little power during operation and incorporates a
power-down pin, enabling power cycling to optimize battery
life in portable applications. The ADPD2211 provides shot
noise limited performance, making it an excellent choice for
measuring signals with the highest possible fidelity in low light
conditions. This combination of low power, very high SNR, and
electromagnetic interference (EMI) immunity enables low power
system solutions not possible with traditional photodiode (PD)
and transimpedance amplifier (TIA) systems.
Rev. 0
Document Feedback
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
©2016 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
1 page  
ADPD2211
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
Supply Voltage (VCC)
Storage Temperature Range
Junction Temperature
Solder Reflow Temperature (<10 sec)
Rating
6.0 V
−40°C to +105°C
110°C
260°C
Stresses at or above those listed under Absolute Maximum
Ratings may cause permanent damage to the product. This is a
stress rating only; functional operation of the product at these
or any other conditions above those indicated in the operational
section of this specification is not implied. Operation beyond
the maximum operating conditions for extended periods may
affect product reliability.
THERMAL RESISTANCE
θJA is specified for the worst case conditions, that is, a device
soldered in a circuit board for surface-mount packages.
Table 3. Thermal Resistance
Package Type
3 mm × 3 mm LFCSP
θJA
68.08
θJC
12.18
Unit
°C/W
Data Sheet
SOLDERING PROFILE
Figure 2 and Table 4 provide information about the recommended
soldering profile.
CRITICAL ZONE
TP tP TL TO TP
RAMP-UP
TL TSMAX
tL
TSMIN
tS
PREHEAT
RAMP-DOWN
t25°C TO PEAK
TIME
Figure 2. Recommended Soldering Profile
Table 4. Recommended Soldering Profile Limits1
Profile Feature
Condition (Pb Free)
Average Ramp Rate (TL to TP)
2°C/sec maximum
Preheat
Minimum Temperature (TSMIN)
150°C
Maximum Temperature (TSMAX)
200°C
Time from TSMIN to TSMAX (tS)
60 sec to 120 sec
Ramp-Up Rate (TSMAX to TL)
2°C/sec maximum
Liquidus Temperature (TL)
217°C
Time Maintained Above TL (tL)
60 sec to 150 sec
Peak Temperature (TP)
260°C + (0°C/−5°C)
Time Within 5°C of Actual TP (tP)
20 sec to 30 sec
Ramp-Down Rate
3°C/sec maximum
Time from 25°C (t25°C) to Peak
Temperature
8 minutes maximum
1 Based on JEDEC Standard J-STD-020D.1.
ESD CAUTION
Rev. 0 | Page 4 of 13
5 Page 
ADPD2211
APPLICATIONS INFORMATION
The current output of the ADPD2211 provides flexibility in
interfacing to external circuitry.
POWERING THE DEVICE
The ADPD2211 is powered from a single positive 1.8 V to 5.0 V
supply. The ADPD2211 features high PSRR, but proper circuit
layout and bypassing is recommended to provide maximum
sensitivity, especially in situations where the ADPD2211 may share
reference nodes with transmitters in pulse mode applications.
Above the quiescent current of the integrated current amplifier,
there is a linear relationship to incident light as the current
amplifier amplifies the photodiode output by a factor of 24. In
typical battery-powered operation, the output of the source
LEDs is dynamically reduced to save power based on the received
signal strength of the photosensor. The extremely low noise
floor of the ADPD2211 provides very high SNR, allowing
accurate signal extraction with minimal source power and at
low incident optical power.
POWER-DOWN MODE
The ADPD2211 is optimized for battery-powered operation by
the inclusion of an extremely low power standby mode that can
be quickly switched to provide ultralow power consumption
during dark periods in pulsed or mode locked applications,
where the light source is cycled to improve ambient light
rejection and reduce transmitter power consumption. The
power-down pin is not internally pulled up or down, and must
be connected to an external logic level for proper operation of
the ADPD2211.
PULSE MODE OPERATION
The ADPD2211 is optimized for battery-powered operation by
the inclusion of a power-down pin (PWDN). When sensing is
inactive, the ADPD2211 can be quickly switched into standby
mode, reducing the supply current to 1 µA during dark periods
for pulsed or mode locked applications, where the light source
is cycled to improve ambient light rejection and reduce
transmitter power consumption.
For multiple wavelength systems, sequentially pulsing the optical
emitters removes the need for multiple narrow bandwidth sensors.
For both multiple wavelength (SpO2) and single wavelength
(heart rate monitoring) systems, pulsed operation can provide
significant power savings for battery-powered systems. Pulsed
mode operation provides a calibration signal that is necessary to
compensate for ambient light diffused throughout the tissue,
which can be extracted by measuring the sensor output while
the system emitters are off. Advanced algorithms can then
extract the signal of interest from dc offsets, noise, and
interferer signals such as motion artifacts.
Data Sheet
OUTPUT CONFIGURATION
The output of the ADPD2211 allows different configurations
depending on the application. The current gain of the ADPD2211
reduces the effect of surrounding interferers but, for best perfor-
mance, careful design and layout is still necessary to achieve the
best performance. The effect of capacitance on the output must
be considered carefully regardless of configuration as bandwidth
and response time of the system can be limited simply by the
time required to charge and discharge parasitics.
Because the ADPD2211 is effectively a current source, the
ADPD2211 output voltage drifts up to its compliance voltage,
approximately 1.2 V below VCC, when connected to an interface
that presents a high impedance. The rate of this drift is dependent
on the ADPD2211 output current, parasitic capacitance, and the
impedance of the load. This drift can require additional settling
time in circuits following the ADPD2211 if they are actively
multiplexing the output of the ADPD2211 or presenting a high
impedance due to power cycling. For multiplexed systems, a
current steering architecture may offer a performance advantage
over a break-before-make switch matrix.
3-WIRE CABLE VOLTAGE CONFIGURATION
The ADPD2211 can be used in a minimal 3-wire voltage
configuration, offering a compact solution with very few
components (see Figure 13). A shunt resistor (RS) sets the
transimpedance gain in front of the analog-to-digital converter
(ADC). This configuration allows flexibility in matching the
ADC converter full-scale input to the full-scale output of the
ADPD2211. The dynamic range of the interface is limited to
the compliance voltage of the ADPD2211.
No additional amplification is needed prior to the ADC. Response
time at the lower end of the range is limited by the ability of the
output current to charge the parasitic capacitance presented to
the output of the ADPD2211.
3-WIRE CURRENT MODE CONFIGURATION
When used in the 3-wire current mode configuration with a
photodiode (see Figure 14), the ADPD2211 is insensitive to load
resistance and can be used when the signal processing is further
from the sensor. EMI noise and shielding requirements are
minimized; however, cable capacitance has a direct effect on
bandwidth, making the 3-wire current mode configuration a
better choice for unshielded interfaces. The feedback capacitance
(CF) value must be chosen carefully to eliminate stability and
bandwidth degradation of the ADPD2211. Large capacitance
around the feedback loop of the TIA has a direct effect on the
bandwidth of the system.
Rev. 0 | Page 10 of 13
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet ADPD2211.PDF ] | |
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