Variation-Aware Circuit Analysis
ChronoVA™/CA
ChronoVA™/CA is a tool to generate a response surface model using
SAP (Stochastic Analysis Process) technique. Given the input parameters
with variation, ChronoVA™/CA quickly and accurately find the response,
similarly as Monte Carlo simulation.
ChronoVA™/CA can be used for simulating the characteristics other
than timing, like the fluctuation of the current or the voltage of an analog
circuit node. As an example, a case is shown below, simulating input voltage
sensitivity of an analog comparator under process variation. The circuit
of this analog comparator consists of generic differential-input OP-amp
using 80 MOS transistors.
First simulation is done assuming the seven transistors in the circuit
have variation on the device characteristics, and others are at the nominal
condition. These seven transistors are known to impact most significantly
to the output. The result is compared with the Monte Carlo simulation with
iterations of 50 thousand times, and show almost perfect match. Using SAP
technology, the iteration count of ChronoVA™/CA is just 36, in other
words, ChronoVA™/CA is 80 times faster than the equivalent Monte
Carlo simulation in terms of the CPU time.
Second simulation is done assuming all 80 transistors have variation. While
it is very difficult to run Monte Carlo simulation with this complexity,
ChronoVA™/CA complete the analysis without significant cost penalty.
In traditional way supposing only seven transistors have variation results
in a little more optimistically.
|
Monte Carlo |
ChronoVA™/CA |
ChronoVA™/CA |
| Variation setting |
Vth on selected ７ Transistors |
Vth on selected ７ Transistors |
Vth and W-gate on all 80 Transistors |
| #Sampling |
50,000 |
36 |
161 |
Result
(Offset from the target) |
Mean |
1.80526E-05 |
3.41003E-06 |
-1.38278E05 |
| Sigma |
0.000942069 |
0.000936020 |
0.00134507 |
CPU Time
(Using 8CPU machine) |
24'52" |
19" |
26" |
|
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ChronoVA™ Family