Shmoo plot
Encyclopedia
In electrical engineering
, a shmoo plot is a graphical display of the response of a component or system varying over a range of conditions and inputs. Often used to represent the results of the testing of complex electronic systems such as computers, ASICs or microprocessors. The plot usually shows the range of conditions in which the device under test
will operate.
For example, when testing semiconductor
memory
: voltage
s, temperature
, and refresh rate
s can be varied over specified ranges and only certain combinations of these factors will allow the device to operate. Plotted on independent axes (voltage, temperature, refresh rates), the range of working values will enclose a three-dimensional, usually oddly-shaped volume. Other examples of conditions and inputs that can be varied include frequency
, temperature
, system- or component-specific variables, and even varying knobs tweakable during silicon chip fabrication producing parts of varying quality which are then used in the process.
Often one 'knob' or variable is plotted on one axis against another knob or variable on another axis, producing a two dimensional graph. This allows the test engineer to visually observe the operating ranges of the device under test. This process of varying the conditions and inputs to the component or system may sometimes be referred to as 'shmooing' but more officially known as electrical testing or qualification. Automatic test equipment
often contains software features that allow automated shmooing of a part.
s, the fictional species created by Al Capp
in the cartoon Lil' Abner. These small, blob-like creatures have shapes similar to the "working" volumes that would be enclosed by shmoo plots drawn against three independent variables (such as voltage, temperature, and response speed).
Electrical engineering
Electrical engineering is a field of engineering that generally deals with the study and application of electricity, electronics and electromagnetism. The field first became an identifiable occupation in the late nineteenth century after commercialization of the electric telegraph and electrical...
, a shmoo plot is a graphical display of the response of a component or system varying over a range of conditions and inputs. Often used to represent the results of the testing of complex electronic systems such as computers, ASICs or microprocessors. The plot usually shows the range of conditions in which the device under test
Device under test
Device under test , also known as unit under test , is a term commonly used to refer to a manufactured product undergoing testing.-In semiconductor testing:...
will operate.
For example, when testing semiconductor
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
memory
Memory
In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....
: voltage
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
s, temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
, and refresh rate
Refresh rate
The refresh rate is the number of times in a second that a display hardware draws the data...
s can be varied over specified ranges and only certain combinations of these factors will allow the device to operate. Plotted on independent axes (voltage, temperature, refresh rates), the range of working values will enclose a three-dimensional, usually oddly-shaped volume. Other examples of conditions and inputs that can be varied include frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
, temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
, system- or component-specific variables, and even varying knobs tweakable during silicon chip fabrication producing parts of varying quality which are then used in the process.
Often one 'knob' or variable is plotted on one axis against another knob or variable on another axis, producing a two dimensional graph. This allows the test engineer to visually observe the operating ranges of the device under test. This process of varying the conditions and inputs to the component or system may sometimes be referred to as 'shmooing' but more officially known as electrical testing or qualification. Automatic test equipment
Automatic test equipment
Automatic or Automated Test Equipment is any apparatus that performs tests on a device, known as the Device Under Test , using automation to quickly perform measurements and evaluate the test results...
often contains software features that allow automated shmooing of a part.
Etymology
The name of the plot is based on ShmooShmoo
A shmoo is a fictional cartoon creature. Created by Al Capp , it first appeared in his classic comic strip Li'l Abner on August 31, 1948, and quickly became a postwar national craze in the USA....
s, the fictional species created by Al Capp
Al Capp
Alfred Gerald Caplin , better known as Al Capp, was an American cartoonist and humorist best known for the satirical comic strip Li'l Abner. He also wrote the comic strips Abbie an' Slats and Long Sam...
in the cartoon Lil' Abner. These small, blob-like creatures have shapes similar to the "working" volumes that would be enclosed by shmoo plots drawn against three independent variables (such as voltage, temperature, and response speed).
External links
- Shmoo Plotting: The Black Art of IC Testing – a 1996 IEEE article by Keith Baker and Jos van Beers.
- Example shmoo plot.
- Shmoo Plot Inventor
