SP504 Ver la hoja de datos (PDF) - Signal Processing Technologies
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SP504 Datasheet PDF : 31 Pages
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Since both VDD and VSS are separately gener-
ated from VCC in a no–load condition, VDD and
aVpSpSrowaicllhebsethsaytmgmeneetrriactaelV. O– flrdoemr
charge
V+ will
pump
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 a minimum of 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 ±l0.5V. The toler-
ance should be ±5% from ±10V. The current
drain for the supplies is used for RS-232 and
RS-423 drivers. For the RS-232 driver, the cur-
rent requirement will be 3.5mA per driver. The
RS-423 driver worst case current drain will be
11mA per driver. Power sequencing is required
for the SP504. The supplies must be sequenced
accordingly: +10V, +5V and –10V. An external
circuit would be needed for proper power sup-
ply sequencing. Consult factory for application
circuitry.
Drivers
The SP504 has seven (7) enhanced independent
drivers. Control for the mode selection is done
via a four–bit control word. 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 the
mode of each driver in the different interface
modes that can be selected.
There are four basic types of driver circuits —
RS-232, RS-423, RS-485 and V.35.
The RS-232 drivers output single–ended signals
with a minimum of ±5V (with 3kΩ and 2500pF
loading), and can operate up to 120kbps.
The RS-232 drivers are used in RS-232 mode
for all signals, and also in V.35 mode where they
are used as the control line signals such as DTR
and RTS.
The RS-423 drivers are also single–ended sig-
nals with a minimum voltage output of ±3.6V
(with 450Ω loading) and can operate up to
120kbps. Open circuit VOL and VOH measure-
ments are ±4.0V to ±6.0V. The RS-423 drivers
are used in RS-449, EIA-530, EIA-530A and
V.36 modes as Category II signals from each of
their corresponding specifications.
The third type of driver produces a differential
signal that can maintain RS-485, ±1.5V differ-
ential output levels with a worst case load of
54Ω. The signal levels and drive capability of
the RS-485 drivers allow the drivers to also
support RS-422 (V.11) requirements of ±2V
differential output levels with 100Ω loads. The
RS-422 drivers are used in RS-449, EIA-530,
EIA-530A and V.36 modes as Category I sig-
nals which are used for clock and data.
The fourth type of driver is the V.35 driver.
V.35 levels require ±0.55V driver output sig-
nals with a load of 100Ω. The SP504 drivers
simplify existing V.35 implementations that use
external termination schemes. The drivers were
specifically designed to comply with the re-
quirements of V.35 as well as the driver output
impedance values of V.35. The drivers achieve
the 50Ω to 150Ω source impedance. However,
an external 150Ω resistor to ground must be
connected to the non-inverting outputs; SD(b),
ST(b), and TT(b), in order to comply with the
135Ω to 165Ω short-circuit impedance for V.35.
The V.35 driver itself is disabled and transpar-
ent when the decoder is in all other modes. All
of the differential drivers; RS-485, RS-422, and
V.35, can operate up to 10Mbps.
The driver inputs are both TTL or CMOS com-
patible. Since there are no pull-up or pull-down
resistors on the driver inputs, they should be tied
to a known logic state in order to define the
driver output.
Rev: A Date:1/27/04
SP504 Multi–Mode Serial Transceivers
15
© Copyright 2004 Sipex Corporation
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