Project Files
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Obsolete Chip Replacement -- Synthesized Sine Wave Generator
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The Instrumentation Laboratory
product incorporated a sole-sourced component that had
become obsolete. Purchasing had located sufficient parts to
last for the product lifetime, but an unexpected contract
manufacturer shortage suddenly left them searching for
parts. The production line would be halted if a fix could
not be implemented quickly. Instrumentation Laboratory hired
Bolton Engineering to develop a small plug-in circuit board
to take the place of the obsoleted component. In less than
two weeks, Bolton Engineering delivered fully functional
boards that plugged into the original chip location,
duplicated the chip functionality, and successfully passed
all tests. |
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 System
Overview
The original system used a
Fairchild ML2036 programmable
sinewave generator. The chip was based on a
Numerically
Controlled Oscillator (NCO) that fed a sinewave lookup
table to an on-chip Digital to Analog (D/A) Converter.
Several dedicated outputs generated reference frequency
outputs for use elsewhere in the system. Bolton
duplicated this functionality in an Altera MAX-II series
240-macrocell Programmable Logic Device (PLD), and used
an external 10-bit serial D/A and op-amp to create the
bipolar analog output. A low-power linear regulator
generated the 3.3V logic supply. The PLD incorporated a
512-entry sinewave lookup table constructed out of a
simpler 128-entry quarter-wave sine wave lookup table
and “unfolding” logic. The PLD was synthesized and
simulated in Altera’s Quartus toolset and the first code
set programmed into the PLD worked without requiring
subsequent changes. The total board size was 1.3” x
2.1”. (including the cut-out region).
Project Scope
Bolton Engineering wrote the specification, designed the
schematics, designed the 4-layer circuit board, wrote
the PLD code, debugged the system, and delivered twelve
working prototypes.
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Consumer and Computer
