SP503 Datasheet, PDF (9/29 Pages) Sipex Corporation – Multiprotocol Transceiver

V_CC = +5V
+
C_{1 –}
+
C_{2 –}
–10V
C₄
+ – _{VDD Storage Capacitor}
– + _{VSS Storage Capacitor}
C₃
Figure 2. Charge Pump Phase 2.
simultaneously with this, the positive side of
capacitor C₁ is switched to +5V and the negative
side is connected to ground, and the cycle begins
again.
Since both V+ and V^– are separately generated
from V_CC 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 15kHz. The external capacitors must
be 22µF with a 16V breakdown rating.
External Power Supplies
For applications that do not require +5V only,
external supplies can be applied at the V+ and
V^– pins. The value of the external supply volt-
ages must be no greater than ±l0V. The current
drain for the ±10V supplies is used for RS-232,
and RS-423 drivers. For the RS-232 driver, the
current requirement will be 3.5mA per driver,
and for the RS-423 driver, the worst case current
drain will be 11mA per driver. The external
power supplies should provide a power supply
sequence of : +l0V, then +5V, followed by –l0V.
Drivers
The SP503 has seven (7) independent drivers,
two of which have separate active–low tri–state
controls. If a half-duplex channel is required,
this can be achieved with external connections.
Control for the mode selection is done via a
four–bit control word. The SP503 does not have
a latch; the control word must be externally
latched either high or low to write the appropri-
ate code into the SP503. The drivers are pre-
arranged such that for each mode of 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. Table 1 shows a sum-
mary of the electrical characteristics of the driv-
ers in the different interface modes. 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.
+10V
C₂₊
GND
GND
C_2–
–10V
Figure 3. Charge Pump Waveforms
Date: 7/29/04
SP503 Multiprotocol Transceiver
9
a)
b)
© Copyright 2004 Sipex Corporation