Featured Medical Application - Telehealth System
Enabling patients to monitor their own health status from home and then relay that data to a remote medical
center is a concept that has seen the
telehealth
industry, though still in its infancy, grow at an exciting rate.
By providing frequent and consistent health monitoring, the frequency of required visits to a clinic or hospital
can be significantly reduced. This may be exceptionally helpful for patients who require non-local care, such as
from a medical specialist.
Simply stated, a telehealth manager is a hub for portable health devices. It interfaces with one or more
personal health monitors allowing a patient to both store the measurement data and send it to the patient’s
physician.
Major subsystems include:
User I/O, such as a display and keypad or touchscreen
MCU
Connectivity: A telehealth manager exchanges data with both a remote medical center and one or more
health measurement devices.
Power Management
As with most Machine-to-Machine (M2M) related technology, the connectivity aspect of
telehealth
design is an important consideration. The Continua Health Alliance has an established set of design
guidelines for creating interoperable personal health solutions, and also offers product certification to
that end.
Microphone
RTC
PMIC
Wireless
Audio Codec
Processor
LED Driver
Ethernet
AMP
Touch Screen
ESD
ESD
RJ-45
Audio Jack
Telehealth System Block Diagram
View Product List
This design is for reference only. The design, as well as the products suggested, has not been tested
for compatibility or interoperability.
Microphones for Telehealth System
microphone
is the device which captures sound waves as they are emitted from their source and passes them on to
be converted into electrical signals for a variety of uses. A MEMS microphone is an extremely small
microphone that operates directly within the semiconductor circuit, acting as a hybrid function of a
microphone and a semiconductor.
Real Time Clocks for Telehealth System
Real Time Clocks
(
RTC
s) are IC devices that keep track of time. A typical RTC can provide the time of day as well as the
date via a serial bus such as I
2
C or SPI. Although similar in many ways, RTCs should not be confused with clock generators, which
are used to synchronize various parts of a circuit.
Power Management ICs for Telehealth System
Power Management Integrated Circuit
(
PMIC
) is a special-purpose IC that provides one or more power management related functions. These can
include voltage regulation, DC/DC conversion, battery management capability and more. Many PMICs
offer an I
2
C and/or SPI bus interface, and some might provide additional features such as an integrated touch
screen interface.
Wireless for Telehealth System
Wireless
technology enables the transfer of information over short or very long distances without cables. The
term "wireless" most often refers to telecommunications. Wireless communication is possible using a
wireless transmitter
and corresponding receiver. A
wireless receiver
refers to the receiving end of the information transfer and requires less energy to operate than the
active transmitting portion where the transfer originates.
Audio Codecs for Telehealth System
codec
is a device that can encode and/or decode a digital data signal. A
codec
encodes data for transmission and/or decodes it for playback. Essentially, a codec has one or more
Digital-to-Analog data converters (DAC) and Analog-to-Digital converters (ADC) in a single package.
A codec is essential for the use of
Digital Signal Processors
(DSPs) in audio applications, since it can convert real-world analog signals (like sound) to digital
signals for the DSP, and back again from digital to analog for the human ear.
Processors for Telehealth System
processor
" refers to an electronic device that performs computational functions and carries out the
instructions of a stored program. Other terms for processor are microprocessor, central processing
unit, and digital signal processor. Essentially, the processor refers to "the brains of a computer."
LED Drivers for Telehealth System
LED drivers
are used in many applications, but in displays they are a constant-current source commonly used to
power LEDs for screen backlighting. LEDs are current-driven devices whose brightness is proportional
to the magnitude of forward current flow. Desirable features for an
LED driver
are tight regulation of current, high efficiency, PWM dimming, overvoltage protection, load
disconnect, small size, and ease of use.
Touch Screen Controls for Telehealth System
touch screen controller
interacts with the touch screen sensor (located between the display and a protective lens that the
user touches) to measure tiny changes in capacitance or resistance. The changes are then translated
into digital signals. The
touch screen controller
interfaces to the host processor to indicate finger/stylus positions, taps, and other useful input.
Some important considerations are the touch screen controller's accuracy, environmental compensation
techniques, ability to handle noise, and efficacy of algorithms.
USB Transceivers for Telehealth System
USB
is a standard connection interface between computers and digital devices. A
USB transceiver
is a physical layer device that prepares data for transmission and then sends to, and receives data
from, another transceiver. The transceiver detects connection and provides the low level USB
protocol and signaling. The term "transceiver" indicates an implementation of both transmit and
receive functions. It transmits and receives, encodes and decodes data, provides error indication,
implements buffers to stage data until it can be managed, and adjusts for the clock rate from the
serial stream on the USB SuperSpeed bus to match that of the "link layer" higher up on the
communication stack.
Ethernet for Telehealth System
Ethernet
is the most commonly used technology for non-wireless local area networks (LANs).
Ethernet controllers
perform the function of interfacing computers and other electronic devices in a network. Ethernet
itself only defines the physical (PHY) and datalink (MAC) layers of the OSI Model; however,
processors with integrated Ethernet controllers can provide additional functions such as a TCP/IP
protocol stack.
Amplifiers for Telehealth System
Amplifiers
have enormous voltage gain, use feedback to operate, and can be classified in different ways. They
can be identified by the device they are intended to drive (e.g., headphone amplifier, speaker
amplifier), the frequency range of the signal (e.g., RF, Audio), and by the function that they
perform (e.g., low noise amplifier, inverting amplifier, power amplifier.)
Touch Screens for Telehealth System
touchscreen
is an electronic visual display that can detect the presence and location of a touch within the
display area. A resistive touch screen works by applying a voltage across a resistor network and
measuring the change in resistance at a given point on the matrix where a screen is touched by an
input stylus, pen, or finger. The change in the resistance ratio marks the location on the touch
screen. With most
capacitive touchscreen panels
, touching the surface of the screen changes the screen's electrostatic field, which is measured as
a change in capacitance. There are different technologies to determine the location of the touch;
but in any case the location is then sent to the controller for processing. Unlike a resistive
touchscreen, most capacitive touchscreens cannot be used with electrically insulating material, such
as gloves.
USB ESD Protection for Telehealth System
Electrostatic Discharge
(
ESD
) is an instantaneous electric current that flows from a higher to a lower voltage potential without
warning. One of the more well-known causes of ESD is static electricity, which is created when
insulator surfaces rub together. Permanent damage can occur to semiconductor devices that are
exposed to
ESD
. An ESD current waveform has an extremely fast rise time. ESD protection chips can be very
effective but consume board space and add some amount of capacitance to an I/O line.
Ethernet ESD Protection for Telehealth System
Electrostatic Discharge
(
ESD
) is an instantaneous electric current that flows from a higher to a lower voltage potential without
warning. One of the more well-known causes of ESD is static electricity, which is created when
insulator surfaces rub together. Permanent damage can occur to semiconductor devices that are
exposed to
ESD
. An ESD current waveform has an extremely fast rise time. ESD protection chips can be very
effective but consume board space and add some amount of capacitance to an I/O line.
RJ-45 Connectors for Telehealth System
RJ-45 connectors
are a type of electrical connector commonly used for Ethernet jacks. The term "RJ-45" is something
of a misnomer, commonly referring to an 8P8C (eight position, eight contact) modular connector with
wiring pin-outs compatible with standard Ethernet.
USB Receptacles for Telehealth System
USB plugs and receptacles
are meant to reduce human error by their unique shape; they fit together in only one way. USB plugs
and receptacles come in Type A (typically connecting to hosts or hubs) or Type B (typically
connecting to devices) and 3 sizes: standard, mini, and micro. Type A plugs always face upstream,
Type B faces downstream.
Audio Jacks for Telehealth System
audio jack
is a
TRS-type
(tip, ring, sleeve) connector commonly used for analog audio signals. The cylindrically shaped
3.5mm jack
can have between two and four conductors to facilitate mono sound (TS), stereo sound (TRS), and
stereo sound with microphone input (TRRS). The sleeve is universally used for ground, and in the
case of a stereo jack, the tip and ring are used for left and right channels, respectively.
Application Notes and Resources
