Shmoo Plots

The Shmoo plot will be illustrated by measuring the effect of power supply reduction on performance:
Nominally, a DUT operates at 1 Volt Vdd with 25 ns delay. A set of test patterns is applied repeatedly to the DUT while sweeping:

• the output delay measured using the compare strobe:
  sweeping variable Delay 1 from 20 ns to 30 ns (x-axis)
• the supply voltage Vdd:
  sweeping variable DUT Power 1 from 0.8 Volts to 1.2 Volts (y-axis)

The expected result of the measurement is:

1. For low supply voltages, the functional test will not pass.
2. At a certain voltage, the DUT will pass functional test at high delay times.
3. Increasing voltage further, the DUT will operate faster.

The DUT behaves as predicted illustrating the anticipated behaviour.
Faulty behaviour may result in other Shmoo shapes with their specific interpretation.

Who is Shmoo anyway?