Embedded Power Supply for Low-

Abstract—The use of dynamically adjustable power supplies as
a method to lower power dissipation in DSP is analyzed. Power
can be reduced substantially without sacrificing performance in
fixed-throughput applications by slowing the clock and lowering
supply voltage instead of idling when computational workload
varies. This can yield a typical power savings of 30–50%. If
latency can be tolerated, buffering data and averaging processing
rate can yield power reductions of an order of magnitude in some
applications. Continuous variation of the supply voltage can be
approximated by very crude quantization and dithering: a four-
level controller is sufficient to get within a few percent of the
optimal power savings. Significant savings are possible only if the
voltage can be changed on the same time scale as the variations
in workload. A chip has been fabricated and tested to verify
the closed-loop functionality of a variable voltage system. The
controller takes only 0.4 mm2
and draws a maximum of 1 mW
at 2 V with a 40 MHz clock. The control framework developed
is applicable to generic DSP applications.