SP334CT Ver la hoja de datos (PDF) - Signal Processing Technologies
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Fabricante
SP334CT Datasheet PDF : 12 Pages
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VCC = +5V
+
C1 –
–5V
+5V
+
C2 –
–5V
C4
+ – VDD Storage Capacitor
– + VSS Storage Capacitor
C3
Figure 15. Charge Pump Phase 3.
VCC = +5V
+10V
+
C1 –
+
C2 –
C4
+ – VDD Storage Capacitor
– + VSS Storage Capacitor
C3
Figure 16. Charge Pump Phase 4.
operation the relative position and functionality
of the drivers are set up to accommodate the
selected interface mode. As the mode of the
drivers is changed, the electrical characteristics
will change to support the requirements of clock,
data, and control line signal levels. Unused
driver inputs can be left floating; however, to
ensure a desired state with no input signal,
pull–up resistors to +5V or pull–down resistors
to ground are suggested. Since the driver inputs
are both TTL or CMOS compatible, any value
resistor less than 100kΩ will suffice.
When in RS-232 mode, the single-ended RS-
232 drivers produce compliant RS-232E and
ITU V.28 signals. Each of the three drivers
output single-ended bipolar signals in excess of
±5V with a full load of 3kΩ and 2500pF applied
as specified. These drivers can also operate at
least 120kbps.
When programmed to RS-485 mode, the
differential RS-485 drivers produce complaint
RS-485 signals. Each RS-485 driver outputs
a unipolar signal on each output pin with a
magnitude of at least 1.5V while loaded with
a worst case of 54Ω between the driver's two
output pins. The signal levels and drive
capability of the RS-485 drivers allow the
drivers to also comply with RS-422 levels. The
transmission rate for the differential drivers is
10Mbps.
Receivers
The SP334 has five single-ended receivers
when programmed for RS-232 mode and two
differential receivers when programmed for
RS-485 mode.
Control for the mode selection is done by the
same select pin as the drivers. As the operating
mode of the receivers is changed, the electrical
characteristics will change to support the
requirements of the appropriate serial standard.
Unused receiver inputs can be left floating
without causing oscillation. To ensure a desired
state of the receiver output, a pull–up resistor of
100kΩ to +5V should be connected to the
inverting input for a logic low, or the
non–inverting input for a logic high. For
single-ended receivers, a pull–down resistor to
ground of 5kΩ is internally connected, which
will ensure a logic high output.
+10V
a) C +
2
GND
GND
b) C2-
-10V
Figure 17. Charge Pump Waveforms
SP334DS/10
Programmable RS-232/RS-485 Transceiver
9
© Copyright 2000 Sipex Corporation
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