Page 20 - Issue 4 2023

ELECTRONICS

step is to develop a product prototype that takes learnings
from the initial prototype work and integrates this into the
end solution. Part of this would be to modify the existing
schematics from the boards used, to remove the superfluous
items (test points, connectors, etc.). The user could then get
started on the PCB development, which would then show off
the importance and usability of the resources we provide with
each of our devices. For example, the optimised demo board
layout is a freely available resource provided for each of our
devices. While the demo board generally looks to be quite
large in size, this is simply to aid the testability and usability of
Figure 7: A functional demo system.
the device. Closer inspection of the board layout reveals that
Demo Build the IC for which the board was developed and the enabling
From a build perspective, the hardware was standard, so circuitry (resistors, capacitors, inductor, etc.) are all designed
no electrical modifications were required beyond some into as small a space as possible to allow customers to bring
adjustments of the LTC4416 thresholds to ensure the correct this into their own layout. This will then provide confidence to
priority for the input power sources. In order to make it more the customer as they know that this is a tested design, which
visually appealing for the event, the boards were mounted they can verify on the bench before building their own version.
on a simple black Perspex sheet using some standard metal For the end application, a larger capacity battery with a
standoffs. higher voltage would help to optimise the amount of charge
The charge current that was being provided for the evening current provided to the USB ports.
was monitored by a simple USB meter. This device visually The CN0509 is a fantastic design and fulfills its
represented how much current was available to charge the requirements perfectly; however, for this particular application,
attendee’s phones. a more slimmed down design could be utilized to reduce the
overall battery bank cost. For example, the LTC7103 and input
How It Performed polarity protection circuitry would not be necessary for this
The demo performed its core function effectively; it design and the isolated flyback could be powered directly from
comfortably charged the battery pack from two alternate the output of the LTC4162 (either 12 V from the AC-to-DC
sources, the handover between sources was managed well by wall wart or the battery voltage once mains power has been
the power path prioritizer, and the CN0509 nicely provided removed).
charge to the connected USB devices. This particular power
bank has another useful feature that many power bank Conclusion
chargers do not have and that is the ability to simultaneously You can certainly prototype a power bank charger, or any
charge the battery pack and the connected USB device. other power supply design for that matter, using some readily
For example, my power bank, which many would consider available hardware and simple power sources. This highlights
reasonably high end, will not charge the phone and the bank that using available demo board hardware can quickly provide
itself at the same time, which is a frustrating limitation. a proof of concept for potential projects without spending
The charge current to the USB port is limited by the much on development. Furthermore, this relatively small but
capability of the LTC4162 with its internal FET design providing valuable step will provide the user with confidence before
a max of 3.2 A – the bulk of the current is sent to the battery committing to a more integrated design. Another point worth
during charging. The remaining current can be used through reiterating is that power supply design and, more specifically,
the USB charger ports. the layout of a power design can be challenging so it is
Any time the input power source is removed, the power worth utilizing the resources available to reduce the overall
path FET on the LTC4162 demo board ensures that the battery development time.
power is redirected to the output port and hence maintains
power to the CN0509 and USB ports. The available charge About the Author
current in this mode drops as per the graph in Figure 4 – since Diarmuid Carey is an applications engineer with the European
the input source to the CN0509 is now the battery voltage, Centralized Applications Center based in Limerick, Ireland.
which is a nominal 7.4 V. He has worked as an applications engineer since 2008 and
joined Analog Devices in 2017, providing design support for
Next Steps the Power by Linear™ portfolio for European broad market
Once the application has been proven to work using some customers. He holds a Bachelor of Engineering in computer
simple, readily available demo boards, the next reasonable engineering from University of Limerick.

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