SP3508EB Datasheet, PDF (8/13 Pages) Sipex Corporation – Evaluation Board Manual

USING THE EVALUATION BOARD
Recommended Equipment
• Oscilloscope
• Digital multimeter
• Signal Generator capable of >40MHz
• Communications Analyzer (such as
Firebird 6000)
Parametric Evaluation
Located on the board are two pins identified
as VCC and SIGNAL GND. Connect VCC
to a +3.3V DC supply. If possible limit the
supply current to 0.5 to 1.0 Amps. Be sure
to have power off when connecting the
supply to the board.
SP3508 Decoder
The SP3508 uses a 3 bit decoder to desig-
nate the protocol selected. There is also a
decoder latch pin available. Table 2 and
Table 3 show the decoder modes for the
driver and receiver. Upon power up the
latch pin needs to be in a transparent state
(logic low or floating) or the SP3508 will be
in an unknown state. Note that D0, D1, and
D2 set as logic high will put the device
shutdown overriding all individual enable/
disable lines and the drivers outputs and
receiver inputs will tri-state. In shutdown
mode the termination resistors also discon-
nect.
Driver Evaluation
Each driver has an internal pull-up; there-
fore, it is in a defined state when the input is
open. Connect a system clock or a signal
generator with a TTL-level output and the
appropriate frequency within the accept-
able range of the driver to the input BNC
connector. Set the jumper to the desired
driver input to be evaluated. There is an
individual enable line for each driver that
can be used to tri-state the driver. Each
enable line has an internal pull up or pull
down to insure the driver is enabled if the
enable pin is not connected or floating. Set
the appropriate jumper to enable the driver
under test. Once the power is on and the
driver input receives a signal, the driver
outputs can be analyzed with an oscillo-
scope or a digital multimeter. Mode selec-
tion can be performed at any time by chang-
ing the jumper settings for the 3 bit decoder
(D0-D2). The appropriate termination for
the driver under test can be added to driver
output and tied to the ground bus.
Receiver Evaluation
The SP3508 receivers have internal termi-
nation appropriate for V.35 and RS-422
modes (refer to the SP3508 datasheet for
more detail on the receiver termination).
This is activated when the receiver is set to
act as a V.11 receiver (see Table 3) and the
TERM_OFF pin is logic “0”. Each receiver
has a fail-safe feature that outputs a logic “1”
when the receiver is open, terminated but
open, or shorted together. There is an indi-
vidual enable line for each receiver that can
be used to tri-state the driver. Each enable
line has an internal pull up or pull down to
insure the receiver is enabled if the enable
pin is not connected or floating. Set the
appropriate jumper to enable the receiver
under test. The mode selection can be
performed at any time after power up by
changing the state of the 3 bit decoder (D0-
D2). To evaluate the receiver the appropri-
ate input signal needs to be applied. This
can be accomplished by providing a signal
from an external source or use the SP3508
driver output and jumper it to the receiver
input. For single ended receivers, tie the
active driver output to the active receiver
input. For differential drivers, tie the “A”
driver output to the “A” receiver input and the
“B” driver output to the “B” receiver input.
Using the TTL signal on the driver input will
allow the user to analyze receiver levels and
timing characteristics.
Rev. 8/28/03
SP3508 Evaluation Board Manual
8
© Copyright 2003 Sipex Corporation