Online proceedings - EDA Publishing Association

11-13
May 2011, Aix-en-Provence, France
V. Characterization results and Conclusions
References
The fabricated device exhibits two output voltages of 9V
and 6.8V, after an initial rise time of 50ms to reach its full
output voltages when excited at its resonant frequency
characterized at 8.32 kHz. There are some discrepancies
between the model results and the characterization. In order to
achieve output voltages of 6.8V and 9V, the distance d RS
between the fingers for C1 and C2 needs to be 7µm and 6µm
respectively. This can be explained, for the most part, by the fact
that the high quality factor Q and the resonant frequency of the
real device F res are slightly different from the ones from the
model (process variation), and we know that the performance is
highly dependent of the driving frequency through the effect this
has on the amplitude. Therefore the “pull-in effect” modeled for
the small rotor to stator spacing gap is not seen yet during
characterization.
Resonant Freq
F res
Output
V out
Analytical model 8.35 kHz 5.8 / 8.2 V
FEM 8.24 kHz NA
MEMS+ 8.26 kHz 5.8 / “pull-in effect”
Characterisation 8.32 kHz 6.8 / 9V
V. Conclusion
Table 3: Results summary.
This paper concerns the modeling and design of a
MEMS single-input, multiple-output DC/DC converter. The
proposed model is in good agreement with the characterization
results. It can be used very rapidly to study the effects of
geometrical and electrical parameters on the whole system
performance. Because of its high output impedance, the present
system is suitable only for purely capacitive loads. More works
need to be done in designing pump charge capacitors with
bigger C 0 values in order to achieve a generic DC-DC converter.
The driving frequency of the MEMS controls the output voltage
of the DC/DC converter. An adaptative and dynamic voltage
scaling can therefore be considered with such MEMS apparatus.
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