SP3508CF datasheet(29/33 Pages) SIPEX

29 / 33 page

Date: 06/14/04

SP3508 Enhanced WAN Multi–Mode Serial Transceiver

TERM_OFF FUNCTION

The SP3508 contains a TERM_OFF pin that dis-

ables all three receiver input termination networks

regardless of mode. This allows the device to be

used in monitor mode applications typically found

in networking test equipment.

The TERM_OFF pin internally contains a pull-

down device with an impedance of over 500k

Ω,

which will default in a "ON" condition during

power-up if V.35 receivers enable line and the

SHUTDOWN mode from the decoder will disable

the termination regardless of TERM_OFF.

LOOPBACK FUNCTION

The SP3508 contains a LOOPBACK pin that

invokes a loopback path. This loopback path is

illustrated in Figure 50. LOOPBACK has an inter-

nal pull-up resistor that defaults to normal mode

during power up or if the pin is left floating. During

loopback, the driver output and receiver input

characteristics will still adhere to its appropriate

specifications.

DECODER AND D_LATCH FUNCTION

The SP3508 contains a D_LATCH pin that latches

the data into the D0, D1 and D2 decoder inputs. If

tied to a logic LOW ("0"), the latch is transparent,

allowing the data at the decoder inputs to propa-

gate through and program the SP3508 accord-

ingly. If tied to a logic HIGH ("1"), the latch locks

out the data and prevents the mode from changing

until this pin is brought to a logic LOW.

FEATURES

There are internal pull-up devices on D0, D1 and

D2, which allow the device to be in SHUTDOWN

mode ("111") upon power up. However, if the

device is powered-up with the D_LATCH at a

logic HIGH, the decoder state of the SP3508 will

be undefined.

CTR1/CTR2 EUROPEAN COMPLIANCY

As with all of Sipex's previous multi-protocol

serial transceiver IC's the drivers and receivers

have been designed to meet all the requirements to

NET1/NET2 and TBR2 in order to meet CTR1/

CTR2 compliancy. The SP3508 is also tested in-

house at Sipex and adheres to all the NET1/2

physical layer testing and the ITU Series V speci-

fications before shipment. Please note that al-

though the SP3508, as with its predecessors, ad-

here to CRT1/CTR2 compliancy testing, any com-

plex or usual configuration should be double-

checked to ensure CTR1/CTR2 compliance. Con-

sult the factory for details.

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