External Use
TM
Xtrinsic Pressure Sensors in the
Medical Market
FTF-HCR-F0174
A P R . 2 0 1 4
Miguel Salhuana | Systems Engineering
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External Use 1
Quick Introduction
• Employed at Motorola / Freescale Semiconductor from February 1995 to
the present, where I’ve had multiple careers. Most recently:
− SoC Integration, Synthesis, Timing Closure and Verification
− Sensor Applications / Product Definition / System Architecture
− basically, solving applications, systems and implementation problems
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Agenda
• How a Pressure Sensor Works
• Pressure Sensor Selection
• Medical Applications
• Development Tools
• Q&A
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Pressure Sensor Basics
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Sensor Basics
• A sensor is a device that detects either an absolute value or a change in a physical or electrical quantity, and converts that change into a useful input signal for a decision making center.
• Pressure (p) is the force (F) applied to a unit area of surface (A) in a gas, liquid or solid. P = F/A
• Atmospheric (Barometric) pressure is due to the weight of the atmosphere (air and water vapor) on the earth’s surface.
Data Processing,
Control, and Connectivity Sensor Input
Output
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Sensor Basics – How Does It Work?
PRT – Piezo Resistive Transducer
Well-established process
temperature variations
A
B
C
D
VIN
Output mV
VOUT
R1
R3 R2
Rg
VOUT = VIN [ R3
R3 + Rg
R2
R1 + R2 ]
Apply Kirchhoff voltage and current laws:
C to V
Converter
P-CELL
PREF
Capacitive Pressure
Transducer Low power consumption
Small Size PCELL
Px
Uncompensated
Compensated
Integrated
TPMS
Satellite Airbag
Timing
Associated System
Change in Resistive Diaphragm
leads to Voltage Shift.
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Sensor Basics – How does it Work?
Pressure Sensor Cross Section
Gauge or Differential Die in the Basic Chip Carrier Package
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Sensor Basics – How Does It Work?
How the Diaphragm Moves • The difference in positive pressure
between the sealed cavity & the
outside pressure, causes the
diaphragm to deflect inward.
• The piezo resistive strain gauge
resistors, located in the diaphragm
itself, detects the deflection of the
diaphragm as a mechanical stress,
resulting in a voltage difference.
• This voltage difference is processed
and amplified to provide the proper
output.
• Sensitivity is primarily a function of
the dimensional characteristics of the
diaphragm itself, especially its
thickness.
No pressure difference
Positive pressure applied
P1
P2
P2
P1
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Sensor Basics – Measurements
Differential P1
P2
Gauge
Absolute
Vacuum
P1
P1
P2 = ATM
Constraint Wafer
For All: P1>P2 for positive voltage output
• The difference in pressure between two points is measured where pressure is applied to both sides of sensor.
• P2 is exposed to the atmosphere and P1 is where pressure is applied.
• Pressure is applied to the top of the die while the bottom of the die is a vacuum sealed reference.
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Sensor Basics – Units
• Pressure (p) is the force (F) applied to a unit area of surface (A) in a gas, liquid or solid
p = F/A
• Atmospheric (Barometric) pressure is due to the weight of the atmosphere (air and water vapor) on the earth’s surface
• The conversions for the most commonly used units are:
1 atm = 101.325 kPa = 760 mmHg = 14.6960 psi
1 psi ~ 28” H2O ~ 70cm H2O ~ 7kPa
bar psi cm water inch of
water
foot of
water
kilopascal
(kPa)
bar 1 14.504 1019.74 401.474 33.456 100.0
psi 0.069 1 70.309 27.680 2.307 6.895
cm of water 0.000 980 0.014 1 0.394 0.033 0.098
inch of water 0.002 491 0.036 2.54 1 0.083 0.249
foot of water 0.029 890 0.434 30.48 12.021 1 2.989
kilopascal
(kPa) 0.01 0.145 10.197 4.015 0.335 1
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Sensor Basics – Question
Who arrived here on a flight?
Phoenix
Drink a bottle of
water, squeeze and
tighten the cap.
Plane
What happens
to the bottle on
the flight?
Dallas
You have arrived,
what does the bottle
look like now?
? ?
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Sensor Basics – Question
Who arrived here on a flight?
Phoenix
Hint:
Phoenix is typically
at 97kPa
Plane
Hint:
Flight Cabin is
typically set to
77kPa
Dallas
Hint:
Dallas is typically
at 102kPa
? ?
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Sensor Basics – Question
Who arrived here on a flight?
Phoenix
Hint:
Phoenix is typically
at 97kPa
Plane
Hint:
Flight Cabin is
typically set to
77kPa
Dallas
Hint:
Dallas is typically
at 102kPa
? ?
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Pressure Sensor Selection
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Sensor Selection – Our Current Products
Uncompensated
Integrated
Design Advantages Design Considerations
• High sensitivity
• Lowest device cost
• Low-level output allows flexibility
of signal conditioning
• Device to device variation in offset
and span
• Temp-compensation circuitry required
• Signal conditioning / amplification
of signal needed
• Reduced device to device
variations in offset & span
• Reduced temperature drift in offset
and span
• Low-level output allows flexibility
of signal conditioning
• No amplification needed,
direct interface with MCU
• Signal conditioning, calibration of
span & offset, temperature
compensation included on-chip
• Lower sensitivity due to span
compensation (compared to uncomp)
• Priced higher than uncomp
• Required signal conditioning /
amplification of output signal
• Priced higher than
uncompensated and
compensated devices
• Lower piece part count on system
PCB
Compensated
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Sensor Selection – Package Options
MPAK
MPAK Axial Port
Super
Small
Outline
Package
(SSOP) Dual
Port
Case
423A
Case
482 Vacuum
Port
Small
Outline
Package
(SOP) Side
Port
Dual
Port
Through
Hole
Axial Port
Case
1317
QFN
Tire
Pressure
Monitor
Axial
Port
Through
Hole 482B Axial
Port
Unibody Medical
Chip Pak
Through
Hole
Axial Port
Through
Hole
Axial Port
LGA
MPL3115A2
5x3x1.2mm
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Sensor Selection – Selecting the Best Pressure Sensor
Step 1: Use Case
• Measurement type: Absolute, Gauge or Differential?
• Pressure range required?
• Sensitivity / Accuracy required?
• Integrated, Compensated, Uncompensated?
Step 2: Environment
• When does the system take a measurement?
• Does the temperature change drastically?
• Is the sensor exposed to chemicals?
Step 3: Implementation Details
• Autozero the pressure sensor (AN1636)
• Media compatibility with the sensor (AN3728)
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Medical Applications
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Blood Pressure Package
Key Features
• Low Cost
• Integrated temperature
compensation and calibration
• Ratiometric to supply voltage
• Polysulfone case material
(Medical, Class V Approved)
• Provided in easy-to-use
tape and reel
Disposable Pressure
Sensors MPX2300DT
A standard invasive blood pressure
monitoring kit - sterile, single-use kits
that relay blood pressure information from
a pressure monitoring catheter to a patient
monitoring system.
Freescale’s MPX2300DT is a low cost, high
volume, miniature pressure sensor package
for the application.
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Blood Pressure Monitors
Position cuff on left
wrist with left thumb
facing upward
Press start button.
Position sensor
detects correct
placement of arm in
relation to the heart.
Once wrist is in the
correct position the
cuff will inflate and take
the measurements.
Reading is displayed
on the LCD screen
Bleed Valve Valve
Control
Motor
Display
Pressure
Sensor
Keypad
Tilt Sensor (Accelerometer)
Voltage
Regulation
Power
Source
MCU
Motor
Control
Bluetooth
Radio
Pressure Monitoring MPXV5050GP
MPXM2053GS
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Negative Pressure Wound Management
Negative Pressure Wound
Management or Closed Wound
Suction (CWS) is a non-invasive
treatment by which controlled
localized negative pressure
(suction) is delivered to a wide
variety of acute, sub-acute, and
chronic wounds.
Negative
Pressure
Wound
Therapy
(N.P.W.T.)
Unit
Air Pressure Management System MPL3115A2
MPXM2053GS
MPXV5100GC6U
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MPL3115A2 in Wound Management
The MPL3115A2 digital pressure sensor essentially can act as a vacuum sensor at altitudes below 10,000 Feet. Broader pressure range is achieved closer to sea level.
MPL3115A2 as
vacuum sensor
MPL3115A2 as
barometric sensor
PUMP
Suction Pressure
about 40 kPa below
Po at 61 kPa
Atmospheric
Pressure, Po at
about 101 kPa
PCB
Wound
BANDAGE
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Patient Monitoring
MPXM2051 Key Features
• Pressure range 0~50kPa gauge
• Temperature compensated
over 0°C to +85°C
• Linearity: +/- 0.3%
• Full scale span: 40 +/- 1.5mV
• Offset: +/- 1.0mV
• Available in easy-to-use tape
and reel
• Ratiometric to supply voltage
• Gauge ported
Blood Pressure Monitor Module MPXM2051 (Measurement)+MPXM2053
(Protection) MPXV5050
CO2 Module MPXV2010 (Flow measurement)
MPL3115A2 (Digital Barometer)
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Respirator Machine
Freescale IPS for
Respiratory Device:
• Wide pressure range
product portfolio from negative
to positive pressure.
• Low pressure range family
(+/-2kPa, 4kPa, 6kPa, 10kPa)
offer design flexibility.
• Ideally suited for microprocessor
or microcontroller-based
systems
• Easy to implement
(no amplifier needed)
• Digital barometer MPL3115A2
offer <1.0kPa accuracy
Air Flow Measurement MPX2010
MPXV7002DP
MPXV5004DP
Barometric Measurement MPXH6115A
MPL3115A2
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Medical Bed/Air Mattress
Prevents • necrosis of the muscle
• pressure sores or
• ulceration
Pressure Monitoring MPX5010DP
MPXM2010GS
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Blood Circulation Therapy
The system provides the optimal
hemo-dynamic profile by applying
intermittent, sequential pressure
to the patient’s leg in a systematic
pattern, increasing the peak venous
velocity (PVV) of venous blood flow
and reducing the risk of clot formation.
Continuous
Enhanced
Circulation
Therapy
(C.E.C.T.)
System
Air Pressure
Management System MPX2010
MP3V5010G
MP3V5050G
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Sleep Apnea
• Positive airway pressure
(PAP) is a method of
respiratory ventilation
used primarily in the
treatment of sleep apnea.
• Barometric measurement
is also critical in some
applications to avoid
altitude deviation.
Continuous
Positive
Airway
Pressure
(C.P.A.P.)
Air Pressure Management System MPXV5004GC6T1
MPXV7002DP
Barometric Measurement MPL3115A2 (Digital barometer)
Cycle of Obstructive Sleep Apnea
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Development Tools
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Medical AFE Demo/Development Kit
Freescale Medical Suitcase • complete development platform
• Tower System eases development of medical applications
• fully integrated solutions set
Has 6 different Analog Front Ends • each focused on a specific medical application
• allows code and hardware reuse
• significantly reduces time to market
Applications Include • 1-Lead ECG
• pulse oximeter
• blood pressure monitor
• glucometer
• spirometer
• ultrasound digital stethoscope
Just plug and play –
ask a sales manager
for a demo today!
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MED-BPM
Complete solution for
design of blood pressure
monitor applications
Features
• Includes isolation circuitry for air
pump and escape valve
• Designed for operation at 3V – 3.3V
• Integrated Freescale
MPXV5050GP pressure sensor
• Schematics, gerber files,
and BOM available
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MED-SPI
• Demonstrates basic
implementation of spirometer
solution
• Includes MPXV7025DP
differential pressure sensor
facilitating air flow measurement
calculation lung capacity
Features
• Minimal components
• Easy to implement
• Schematics, gerber files,
and BOM available
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Xtrinsic Sensor Expansion Boards
Differentiators • First 12-axis Freedom Platform
• First with Sensor Fusion Toolbox Android app
• Scalable toolset with 3 options shown (see next slide)
• Plugs into Freedom Development Tools
FRDM-FXS-MULTI Xtrinsic Shield board • MPL3115A2 – Altimeter/pressure sensors
• MMA8652 – 3-Axis Accelerometer 2x2mm
• FXAS21000 – 3-Axis Gyroscope
• FXOS8700 – 6-axis Ecompass Sensor (accelerometer +magnetometer)
• FXLS8471 – 3-Axis Accelerometer 3x3mm with SPI
• MMA955x – Intelligent Sensor with 3-Axis accelerometer and 16Kb flash (ADD 32 bit micro)
• MAG3110 – 3-Axis Magnetometer 2x2mm
Relevant Documentation • Quick Start Guide and installations instructions provided
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Xtrinsic Sensor Expansion Boards
Part Number Description Pricing
FRDM-FXS-MULTI-B* Xtrinsic Sensor Expansion board w/ Bluetooth and Battery, MPL3115A2 MMA8652 FXAS21000 FXOS8700 FXLS8471 MMA955x MAG3110
$125
FRDM-FXS-MULTI* Xtrinsic Sensor Expansion board MPL3115A2 MMA8652 FXAS21000 FXOS8700 FXLS8471 MMA955x MAG3110
$50
FRDM-FXS-9AXIS* Xtrinsic Sensor Expansion board with only 2 sensors : FXAS21000 FXOS8700
$30
Kinetis KL25z compatible Xtrinsic Sensor Expansion Boards
KL25z
*Boards are compatible with the KL25z, KL26z and the K20D50M Freedom Boards.
FRDM-FXS-
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Differentiators
• Proven technology and reliability
• Unique technical capabilities
− Broad technical portfolio for sensing ranges
− Packaging capabilities and varieties
− 30+ years of sensor design experience
• Development tool chest for fast prototyping and development
• MCU partnership to deliver complete embedded system solutions
• Complete system solution with MCU, Sensors, Analog, Networking
and RF communication.
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© 2014 Freescale Semiconductor, Inc. | External Use
www.Freescale.com
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© 2014 Freescale Semiconductor, Inc. | External Use
www.Freescale.com
Backup Slides
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Sensor Integration + Intelligence =
Xtrinsic Sensing Solutions
• Increasing levels of integration
− Sensor signal processing
− Nonvolatile storage
− I/O interfaces
• Intelligent Software Framework
− Data acquisition
− Power management
− Connectivity
• Increasing levels of intelligence
− Programmability
− Auto-calibration
− Sensor fusion
− Third-party software ecosystem
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Sensor Basics – Ranges
Water level sensing in Washing Machines 40cm of H20 4
Engine Map Sensor 3 to 48psi 20 to 304
Medical Respiratory 0.5 to1.45psi 4 to 10
Altimeter/Barometer 2.9 to18.8psi 20 to 130
Tire Pressure Monitoring 14.5 to 120psi 100 to 800
Sea Level 1atm=14.9psi 101.3
Dead Sea-Lowest point on earth -1300ft 15.4psi 106
Everest-Highest point on earth +30,000ft 4.8psi 33
Space-Low density Extremely low close to Vacuum 0psi ~0
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Sensor Basics – How Does It Work?
Diaphragm
Ion-implanted
Strain
Gauge
Single Chip Integrated Silicon Pressure Sensor
Signal
Conditioning
Circuit
Our IPS Technology
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Sensor Basics – Absolute Sensors
Dead sea – Lowest point
on earth -1,300ft, 106kPa
Everest - Highest point
on earth +30,000ft, 33kPa
Barometer
Altimeter
Tire Pressure
Engine Control
• Each needs a pressure measurement that
is compared to a fixed reference (vacuum)
• Sensor is in an enclosed environment with a
pressure medium
Point B
Point A
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Sensor Basics – Gauge Sensor
• Each needs a measurement that compares the
barometric pressure in its surroundings to the
measurement pressure
• In general, anything below 10 psi (70 kPa)
Blood Pressure
Water Level
Leak Detection
Test Equipment
Atmospheric pressure
Sealed tube of air/water column
Pressure Sensor measuring with reference to atmospheric pressure.
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Sensor Basics – Differential Sensor
• Each requires a comparison of the
pressure between two ports of the sensor
• Flow measurement
HVAC Applications
Air Flow
Filter Pressure
Pressure Drop
DP= f(V)
Pressure Sensor measuring with a difference in pressure
between two pressure points
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Sensor Selection – Our Current Products
MPX5010DP
COMPENSATED + CALIBRATED + AMPLIFIED = INTEGRATED
MPX2010DP
COMPENSATED
& CALIBRATED
Temperature
compensation Amplification
Amplification
MCU
MCU
MCU
Output
Output
Output
MPX10DP
BASIC ELEMENT
Altitude: MPXM2102A
Altitude: MPXA6115A
MPX5100A
MPX4115A
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Sensor Selection – Our Current Products
M PX V 5 010 G C 6 U DEVICE CATEGORY M Qualified standard S Custom device P,X Prototype device
FAMILY - Uncompensated 2 Temp Comp & Calibrated 4 - 6 Amplified
Maximum Rated Pressure (kPa) except MPX2300 expressed in mmHg.
MEASUREMENT TYPE A Absolute D Differential G Gauge V Vacuum
SHIPPING METHOD
- Trays
T1 Tape & Reel
U Tube
PORTING OPTION
P Side Port Porting
DP Differential Porting
VP Vacuum side Porting
C,S Axial port
SOP LEAD BENDING
6 Gull wing leads
7 Leads 84° bent towards
the bottom
PRESSURE SENSORS
PACKAGE SELECTION - Unibody A Absolute Small Outline Package (SOP) C Chip Pak H Super Small Outline Package (SSOP) L LGA M MPAK V Vented Small Outline Package Y CMOS Z Media Resistant Gel
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TWR-
K53N512
TWR-SER
TWR-LCD
Tower
System
EBI
USB
Includes Freescale Technology
Medical
Connector
MED-SPO2
MED-EKG
MED-SPI
MED-BPM
MED-GLU
MED-
STETH
Medical Suitcase Block Diagram
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High-End Blood Pressure Monitor (BPM) + spirometer (highlight freescale parts) add pressure sensor
Kinetis K50
VREF PDB
2 x ADC ACMP
TRIAMPS
OPAMPS
SPI
TSI
LCD
CNTRL
Segment
Display
External
Bus
Touch
Pad
DC
Brush
Motor
CNTRL
Graphic
Display
NVM
Pump
motor
Bleed
valve
ARM
Cortex
M4™ CPU
SW
Filter
Pressure
Sensor
MPXV5050GP
USB Ethernet
Analog Sensors Peripherals
Optional Internal Modules
Pressure
Sensor
MPXV7025DP
500 Hz
Low
Pass
Filter
Add a spirometer
with the 2nd ADC
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Blood Pressure Monitor
• A blood pressure monitor uses
techniques such as oscillometric
methods and Korotkoff’s
measurements to measure
blood pressure
• The oscillometric method consists
of measuring the oscillations in
pressure inside a cuff that the
patient wears. The Korotkoff
method is based on listening to
sounds when taking blood pressure
• Automatic blood pressure
monitoring conducted at home is
increasingly used in the diagnosis
and management of hypertension
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Design Challenges – Blood Pressure Monitor
Problem Solution
Measurement accuracy Increase the ADC resolution
Battery oriented Extreme low power consumption specially
Appropriate display Segment or graphic LCD display capability
Pressure Sensor Medical-grade pressure sensors, signal conditioning inside
the MCU
Connectivity Wires and/or wireless communication capability
Low cost BOM reduction, hardware design optimization
Algorithm complexity Cost-effective CPU performance
Added value & differentiators Internal sensing, touch sensing
Motor Control External controller via SPI, or with the internal TPM module
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MED-BPM State Measuring Flow Diagram
MAP (Mean Arterial Pressure)
Maximum Amplitude of all Pulses
Max pressure not reached
Find higher
point in pulse
Ignore first
samples
Find lower
point in pulse
Store pulse
amplitude and
cuff pressure
value
Calculate
arterial
pressure
values
Show Results
Stop inflating
cuff and open
escape valve
70% of MAP. Pressure in cuff
Above MAP
50% of MAP. Pressure in cuff
Below MAP
• MED-BPM demo uses Ramp-Up method (variation of oscillometric).
• Air pump starts to inflate the cuff.
• While inflating, for each oscillation the main cuff pressure is taken and the oscillation amplitude is saved.
• When the pressure has reached a maximum value, motor stops inflating and valve opens in order to deflate the cuff.
• While cuff is deflating, calculations are performed.
• All the pulses are checked in order to find the one with the biggest amplitude.
• Pulse with the biggest amplitude represents the MAP (Mean Arterial Pressure), and the main cuff pressure recorded during this pulse is registered as the MAP.
• Systolic and Diastolic arterial pressures are calculated.
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Demo: MED-BPM
Air
Pump
Arm Cuff
Air
Valve
Pressure
Sensor
MP3V5050
GPIO
GPIO Op
toco
uple
r
Low
Pass Buffer with
internal
OpAmp
AD
C
Signal
Amplifier
with
internal
OpAmp
High
Pass
ADC
Low
Pass
Freescale Part
MM/K5X Internal
Non electrical connection
Measure pressure from cuff
Amplify pulses to detect
maximum peaks
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MED-BPM
MED-BPM Running
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MED-EKG
• Auxiliary board for development of electrocardiography and heart rate monitoring
• Speeds up development time, scalable and adjustable to final product needs
Features
− Tower System compatible
− Integrates all required components for electrocardiograph development
− Four finger electrodes
− External electrode capable for increased accuracy
− MC56F8006 DSC included on board
www.freescale.com/MED-ECG
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MED-SPO2
• Pulse oximetry
development ideal for
SpO2 measurement or
beats per minute (bpm)
determination using non
invasive procedures
Features
− Tower System compatible
− Full integration
− Size optimized
www.freescale.com/MED-SPO2
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MED-GLU
− Single-board glucometer solution
− Eases design
Features
− Size optimized
− Tower System compatible,
opening complete suite of
solutions including
serial communications
LCD displays
wireless connectivity
− Schematics, gerber files,
and BOM available
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MED-STETH
• Complete digital stethoscope solution using ultrasonic waves
• Complimentary to design of fetal heart rate monitors
Features
− Tower System compatible
− Application software available
− Designed for use with TWR-LCD,
a 16-bit color TFT-LCD display
for vivid graphics
− Schematics, gerber files,
and BOM available
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External Use 55
Nonin Pulse Ox
MC9S08GP32
The Home Health Hub Platform
868MHz RF
Thermometer
HHH Panic Alarm
MC12311
Wired connection
Wireless connection
Medical monitoring
WWW connection
TELE-HEALTH
Weight Scale Blood Glucose
Meter
Bluetooth
Low Energy Bluetooth
SPP
Bluetooth
HDP
HHH Ref Platform
Gateway
i.MX28
i.MX53 Tablet
With Medical User
Interface
Physician
Social Networking
Monitoring Center
Loved Ones
Social Network
Home Health Hub Ref Platform Expansion Capabilities Smart Plugs
Smart Appliances
Safety/Security
Lighting Control
Local Display
HOME AUTOMATION
Ethernet
Blood Pressure
Monitors
USB
PHDC
HealthCare
TM
© 2014 Freescale Semiconductor, Inc. | External Use
www.Freescale.com