SP3220B Ver la hoja de datos (PDF) - Signal Processing Technologies
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SP3220B Datasheet PDF : 18 Pages
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Phase 4
— V transfer — The fourth phase of the clock
DD
connects the negative terminal of C2 to GND,
and transfers this positive generated voltage
across C to C , the V storage capacitor. This
2
4
DD
voltage is regulated to +5.5V. At this voltage,
the internal oscillator is disabled. Simultaneous
with the transfer of the voltage to C4, the positive
side of capacitor C1 is switched to VCC and the
negative side is connected to GND, allowing the
charge pump cycle to begin again. The charge
pump cycle will continue as long as the
operational conditions for the internal oscillator
are present.
Since both V+ and V– are separately generated
from VCC; in a no–load condition V+ and V– will
be symmetrical. Older charge pump approaches
that generate V– from V+ will show a decrease in
the magnitude of V– compared to V+ due to the
inherent inefficiencies in the design.
The clock rate for the charge pump typically
operates at 250kHz. The external capacitors can
be as low as 0.1µF with a 16V breakdown
voltage rating.
ESD Tolerance
The SP3220B/U device incorporates ruggedized
ESD cells on all driver output and receiver
input pins. The ESD structure is improved over
our previous family for more rugged applications
and environments sensitive to electro-static
discharges and associated transients.
The Human Body Model has been the generally
accepted ESD testing method for semiconductors.
This method is also specified in MIL-STD-883,
Method 3015.7 for ESD testing. The premise of
this ESD test is to simulate the human body’s
potential to store electro-static energy and
discharge it to an integrated circuit. The
simulation is performed by using a test model as
shown in Figure 20. This method will test the
IC’s capability to withstand an ESD transient
during normal handling such as in manufacturing
areas where the ICs tend to be handled
frequently.
Rev. 7/8/03
SP3220B/U +3.0 to +5.0V RS-232 Transceivers
12
© Copyright 2003 Sipex Corporation
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