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3 – 14
Application notes
can be used to stabilize the 6 V filtered voltage to load independent
5 V.
The following output ripple measurements in figures 3.9 and 3.10
illustrate the enormous advantages of sinusoidal drive DC-DC con-
verters.
TDS 3034 7 Aug 2008 09:25:12
Figure 3.9: Noise measurement for 500 kHz square wave drive pro-
ducing an output voltage of
6 V at 100 mA load. At 10 mV per
division vertical oscilloscope gain the e ective scale is 400 V per di-
vision. Every edge on the driving voltage causes large transients with
a peak amplitude of 1.67 mV
and an RMS amplitude of 88 V
.
rms
peak
All measurements were taken with a SIM914 dual 350 MHz preamp
with both channels in series, giving an equivalent gain of x25 in
addition to the oscilloscope's vertical gain.
Most of the spectral energy in the ripple of the sinusoidal drive
converter is in the fundamental and second harmonic frequency.
Both components can be further reduced by carefully controlling
the current loops in the circuit and are by no means optimal. The
circuit at this point was so sensitive to wiring geometry that no
further reduction was attempted since the ultimate performance will
depend on the particular application of this converter. However, one
can estimate from the result that peak-peak ripple of 50 V
and
pp
RMS noise on the order of less than 10 V
is a realistic design goal.
rms
For improved common mode rejection, the transformer should be
SIM954 300 MHz Dual Inverting Driver Amplifier
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