|
Examples of Typical Analog Circuit Design
Engagements
This
section describes some typical projects that we have been involved with
in the past. The examples include the background, what was done to
assist the project and the results.
Examples
of Projects
Design
Reveiw and Analysis of a Hot Insertion Circuit
Situation
Client was Designing a Hot Board Insertion circuit
and was concerned about the ability of the Power Supply to sustain the
"current spike" presented by this new circuit design. They lacked the
engineering capacity to create the appropriate Spice Simulation models
and verify them in the actual system.
Tasks
Performed
Created a model for the hot insertion portion of the
circuit that included a MOS FET, and its associated components. Ran
simulations. Ran tests in the Lab to verify how well the models
performed in relation to the actual circuitry. Updated the model until
it validated what was measured in the system.
Results
Client was able to be assured that the new design would
function adequately in mass production without manufacturing test and
field failures.
Analog
Design Interface for High Speed PCB
Situation
Client needed someone to follow the layout of a high
speed PCB design to assure that the High Speed signals would allow the
various ICs to communicate with each other both between and internal to
the boards.
Tasks
Performed
Worked with the client to identify the critical signals
on the schematics. Assistance was given to select the appropriate PC
Board material. Layout rules were generated for the layout person to
follow. Interfaced with the layout person to answer questions during
layout, and to check on progress.
Performed
checks of critical lines after layout was complete to assure that
layout rules were followed correctly.
After
board was fabricated, tests were run to assure the critical lines had
the correct impedance. Measurements were made on the Assembled board to
assure that signal integrity was maintained.
Results
There were very few problems areas related to layout on
the board when circuit functionality was tested. This prevented the
need for a massive relayout that would have seriously extended the
schedule.
Design
of a High Performance, Low Noise Amplifier Circuit
Situation
Client had insufficient knowledge of analog electronics
to create a special amplifier for very low level, wide bandwidth
signals for a high performance photodiode amplifier to feed a high
speed analog to digital converter.
Tasks
Performed
Worked with the client to identify the specifications
required for the new circuit. Created a model and block diagram for the
circuit architecture and did initial simulations for estimated
requirements.
Searched
through available operational amplifiers and their characteristics to
come up with suitable candidates for the design. Captured the
schematic. Indicated critical signal lines on the schematic for layout
person. Created a formal Spice model of the circuit and simulated it
before it was fabricated. Reviewed layout before fabrication. Tested
the circuit after the PCB was fabbed and assembled. Included validation
of Spice Model simulation.
Results
Created a design that met the circuit specifications
and that permitted the design to be available in rapid time.
Design
of a Special Purpose Driver Circuit
Situation
Client was doing a redesign of an existing PCB design
to expand the capabilities of a circuit, and at the same time shrink
its size. They wanted the circuit to be simple, and not to utilize a
microcontroller. This would keep development costs low. The circuit was
to take in a standard interface, and drive a number of digital outputs
using a standard Windows program as a driver.
Tasks
Performed
Created a specification and a plan to develop the PCB.
This included a block diagram and an initial selection of critical
components. Captured the schematic of the circuit. Interfaced with the
layout person to get PCB layed out properly, then checked results
before fab. Interfaced with Fab and assembly houses to make model PCBs.
Tested
PCBs and made them functional. Documented the entire design, and worked
with client to make it ready for production. Held the necessary Design
and Status Reviews throughout the project.
Results
A PCB that met all of the circuit specifications, and
that permitted the client to test a new approach to the system design
in record time. The design was largely ready for production, once proof
of concept was assured.
Design
of a Low Power, Battery Operated Analog Circuit
Situation
Client was creating a proof of concept model for a
mixed signal, battery powered very low power circuit. The circuit
received information via a photocell, that was encoded in the video of
a TV Raster.
Tasks
Performed
Created a specification and a plan to develop the
circuit. This included a block diagram and selection of low power
circuit techniques and components. Designed and captured the schematic
of the circuit. Interfaced with layout person to create a PCB model of
the circuit. Led and interfaced on the Fab and assembly of the circuit
board.
Tested
PCBs and made them functional. Documented the entire design, and worked
with client to make it ready for incorporation into the mixed signal
ASIC. Held the necessary Design and Status Reviews throughout the
project.
Results
A circuit was created that met all of the circuit
specifications, and that permitted the client to test o the system
design in record time. The final design was successfully incorporated
into the ASIC, once proof of concept was shown.
|
