How Can Something
So Small Be So Powerful?
By Sam Brusco, Associate Editor
It’s nothing new that medical devices are becoming more portable — the explosion of wearables has proven that. But making these technologies smaller and smarter is a challenge for power management.
A sophisticated set of functions requires quite a bit of processing
power, which must somehow be enclosed in devices that are constantly shrinking. Batteries typically
take up the most space in a portable device, so
what can be done within the limitations of space to
optimize power? To assess this, MDT spoke with
Kaushal Vora, senior manager of product marketing
at Renesas Electronics America. Here’s what he had
to say about powering portable healthcare:
Brusco: What steps is Renesas taking in power
source design for connected portable devices?
Vora: Renesas microcontrollers (MCUs) and
microprocessors (MPUs) have a flexible power
management architecture. The power source for a
connected portable/hand-held device is typically a battery – either a
single charge, rechargeable lithium-ion (Li-ion) or Li-poly. Our solutions make sure the power drawn from these sources is optimized,
resulting in extended battery life for the end product.
The customer’s goals are typically to minimize the cost and size
of the power source while making it last longer. Our MCUs and
MPUs support that with the ability to operate in multiple power
modes, dynamically switch between modes intelligently, and turn
on/off blocks individually as needed to minimize power draw. The
new Renesas Synergy Platform also adds complementary software
that makes it extremely easy and efficient to manage power.
Brusco: What are the challenges in powering microcontrollers?
Vora: The challenge is not so much with powering the MCU
itself but the overall system power. Because the MCU has a
flexible power architecture, it usually has the intelligence to
put itself in a very low-power state, which can be >90% of the
time in a battery-operated application. The biggest culprits are
sensors that must be on all the time, LCD displays, fuel-gauge/
battery management ICs, and high-brightness LEDs. The MCU
is responsible for turning these subsystems on and off to optimize
overall system power consumption.
Brusco: What are the challenges of powering smaller
and smarter devices?
Vora: More devices are becoming wearable, for instance
in fitness and tracking applications, or in cases where a device
continuously monitors a chronic/acute condition but is still small
enough to be tucked away under clothing.
The biggest challenge is the size and life of the battery. We ad-
dress that with a highly flexible and configurable hardware and soft-
ware power management architecture. As devices get smarter, more
performance is expected while still keeping size and
power in mind. Products that can efficiently manage
complex processing with both hardware and soft-
ware features are critical. Renesas offers embedded
solutions for this level of processing power, including
low-power, high-performance RX MCU devices
and our Synergy platform with features that support
complex multi-sensor processing and sensor fusion.
We have hardware blocks that can do complex math
functions more efficiently, a floating point unit to do
complex math efficiently, a DSP library, as well as a
highly efficient real-time operating system.
Brusco: What power considerations must be made
for different use cases?
Vora: This depends on the use case. In a blood glucose meter, for
example, there are typically three modes of operation: Measurement
Mode, User Mode, and Stand-by/Sleep Mode.
Measurement Mode is when the device makes the measurement and runs the algorithm. In this mode, the system is going
full blaze and the power consumption is the highest. This only
happens maybe four to five times a day, so efficient processing in
the MCU will help optimize the power consumption.
User Mode is an intermediate power mode, where processing
is not heavy but the HMI (human machine interaction) functions
like switch/button presses and LCD/LED display are consuming
power, for example when the user presses a button and views the
result or history on the LCD screen, which happens maybe six to
eight times a day. An intermediate power mode in the MCU helps
conserve power by operating the machine at a lower speed and
turning off subsystems that are not needed or used.
Systems typically spend >90% of their lifetime in Stand-by/Sleep
Mode. To extend battery life, it is important to have a very efficient
stand-by/sleep power mode that ensures very low leakage. Having
a good software and hardware power architecture centered around
the MCU is critical.
Brusco: What are the advantages of using Bluetooth Smart?
Vora: Bluetooth Smart (a.k.a. Bluetooth Low Energy) is the
most popular low-power, short-range wireless connectivity stan-