HC55180 Datasheet, PDF (15/19 Pages) Intersil Corporation – Extended Reach Ringing SLIC Family

HC55180, HC55181, HC55182, HC55183, HC55184
Uncommitted Switch
Overview
The uncommitted switch is a three terminal device designed
for flexibility. The independent logic control input, SWC,
allows switch operation regardless of device operating
mode. The switch is activated by a logic low. The positive
and negative terminals of the device are labeled SW+ and
SW- respectively.
Relay Driver
The uncommitted switch may be used as a relay driver by
connecting SW+ to the relay coil and SW- to ground. The
switch is designed to have a maximum on voltage of 0.6V
with a load current of 45mA.
+5V
RELAY
SW+
SW-
SWC
FIGURE 12. EXTERNAL RELAY SWITCHING
Since the device provides the ringing waveform, the relay
functions which may be supported include subscriber
disconnect, test access or line interface bypass. An external
snubber diode is not required when using the uncommitted
switch as a relay driver.
Test Load
The switch may be used to connect test loads across Tip
and Ring. The test loads can provide external test
termination for the device. Proper connection of the
uncommitted switch to Tip and Ring is shown below.
TIP
RING
TEST
LOAD
SW+
SW-
SWC
FIGURE 13. TEST LOAD SWITCHING
The diode in series with the test load blocks current from
flowing through the uncommitted switch when the polarity of
the Tip and Ring terminals are reversed. In addition to the
reverse active state, the polarity of Tip and Ring are reversed
for half of the ringing cycle. With independent logic control
and the blocking diode, the uncommitted switch may be
continuously connected to the Tip and Ring terminals.
42