Rev. 8/28/03

SP3508 Evaluation Board Manual

© Copyright 2003 Sipex Corporation

8

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

USING THE EVALUATION BOARD

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.