26
®
ArC Instruments Ltd.
VolatilityRead
Apply a single pulse and then measure the
transient response of the device.
The VolatilityRead module begins by applying a
single square-wave pulse with parameters
specified by the ‘Pulse Amplitude’ and ‘Pulse
Width’ fields. Subsequently, the instrument starts
measuring the resistive state of the device at its
maximum sampling rate of 200 ksps. By default,
100 of these ‘spot reads’ are averaged to yield a
single assessment of the resistive state of the DUT,
although the user may change that value through
the ‘Average cycles/point’ field. Once B resistive
state assessments have been collected (user-
defined, ‘Read Batch Size’ field, max. 1000) the
system will interrupt its read-out sequence and
transmit data from the microcontroller to the PC,
following which the procedure will repeat for as
many batches as are required until a stopping
condition is met.
The volatile read module can be configured to use three possible stopping conditions:
a)
Fixed time: the system will continue reading batches of data until the ‘Stop time’ is reached.
Note: Once a data batch has started it will finish even if it ends after the prescribed stop time.
b)
Linear fit: The system will fit the resistive state of each batch with an affine relation. If the
absolute slope measured in % change of resistive state per batch drops below the value
specified by the ‘Stop Tol.’ field, the system considers the device to be at rest and the test run
ends.
c)
T-test: The first and last 25 data points in the batch are processed as two populations of
measurements on which the t-test is applied. The t-metric is then computed:
𝑡 =
µ
1
− µ
2
√
𝜎
1
2
𝑛
1
+
𝜎
2
2
𝑛
2
where t is the t-metric,
µ
are the means of the two populations,
σ
their variances and n the
number of samples in each population.
The test ends when a batch featuring a t-metric below the user-
defined threshold (‘Stop t
-
metric’ field) is obtained.
Note: Regardless of stop condition chosen the volatility module will always obey the ‘stop time’
condition as a safety precaution.
Note: When choosing a stopping condition from the drop-down menu the relevant stopping
condition text fields are highlighted in red.
Figure 30: Volatility module interface.