IEEE Power Electronics Magazine - December 2019 - 88

White Hot

by Robert V. White

Programmable
Power Supply Controllers

S

ometime around 1986, I was
working in one of the power sup-
ply design groups at the Digital
Equipment Corporation ("Digital" or
"DEC"). One day I was working with
another engineer in the group, Gedaly
"Gedy" Levin. We were reviewing data
sheets for power supply control integrat-
ed circuits (ICs) to pick one for a new
project. We had several chips from
which to choose, but none did exactly
what we wanted. For example, the
UC3842 controller needs external cir-
cuitry to implement a soft start function.
During this process, Gedy noted that it
would not be difficult to make a control
chip with all of the various functions and
the ability to program how they were
connected and how they worked. He
wondered why this was not being done.
Today, we do have various digital
solutions. There are power supply con-
trol ICs that are basically fixed in their
architecture, but that can have operat-
ing parameters customized by pro-
gramming over a serial bus, such as
the PMBus. There are also full digital
control solutions ranging from simple
8-b microcontrollers to high perfor-
mance 32-b digital signal processors.
Those are not the topic of this column.
I will write about those after I have a
chance to see the latest and greatest at
the IEEE Applied Power Electronics
Conference and Exposition in New
Orleans, Louisiana, in March 2020.
Digital Object Identifier 10.1109/MPEL.2019.2947767
Date of current version: 17 December 2019

88

IEEE POWER ELECTRONICS MAGAZINE

Fast-forward several years and
Cypress Semiconductor introduced
its Programmable System on a Chip
(PSoC). This chip had a proprietary
8-b microcontroller surrounded by
programmable digital and analog
peripherals. In some ways this was
the fulfillment of Gedy's original
vision. The second generation of
PSoC changed the microcontroller
part to an 8051 core.
The early PSoCs could be used in
power supply control. While I did not
use them myself, I saw them being
used in the company at which I was
working at the time. The functionality,
for a power supply control application,
was limited, and the parts did not have
a good debug capability. To debug,
one wrote the code, programmed
("burned") it into the PSoC, and put
the PSoC into the circuit. If it did not
work as desired, one could not attach a
debugger to investigate the code as it
operated, such as running the code
step by step. One had to observe the
operation, and try to deduce the error
in the code. You then edited the code,
programmed the PSoC, and put it back
in the circuit in a cycle known as burn
and pray. This was obviously not an
efficient way to develop code.
The PSoC has evolved, adopting
ARM cores; but Cypress has moved
the PSoC in a direction that is aimed
at supporting the Internet of Things,
the human-machine interface, and
related applications. The peripherals
are aimed at sensors and high-speed

z	December 2019

communication, rather than those
that support making a custom power
supply controller. I do admit that this
is probably the right business deci-
sion for Cypress.
Along the way, field-programmable
analog arrays (FPAAs), modeled after
digital field-programmable gate
arrays (FPGAs), were created and are
available. These, however, have been
aimed more at signal processing and
signal conditioning applications than
control, and especially, power con-
verter control. These have failed to
gain any significant share in the mar-
ket. Signal processing is a fussy busi-
ness, and there are so many op-amps
and other signal processing chips
available that FPAAs never took off.
Bill Schweber, a well-known analog
IC and analog applications engi-
neer, recently explored this in a blog
entry on the Digi-Key website (https://
www.digikey.com/en/blog/whatever
-happened-to-programmable-analog).
Silego, now part of Dialog Semi-
conductor, developed a programmable
analog and digital chip called the
GreenPAK. This is an interesting prod-
uct, and it solves many problems for
customers that need to squeeze in
some custom functionality into a mini-
mum amount of board space. One
drawback of the GreenPAK product is
that it is only one-time-programmable.
That means you only get to program
the chip once. If you make a mistake
(continued on page 86)
https://www.digikey.com/en/blog/whatever-happened-to-programmable-analog https://www.digikey.com/en/blog/whatever-happened-to-programmable-analog https://www.digikey.com/en/blog/whatever-happened-to-programmable-analog
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