HC55185_06 Datasheet, PDF (16/20 Pages) Intersil Corporation – VoIP Ringing SLIC Family

HC55185
High Voltage Decoupling
The 100V rating of the device will require a capacitor of
higher voltage rating for decoupling. Suggested decoupling
values for all device pins are 0.1μF. Standard surface mount
ceramic capacitors are rated at 100V. For applications driven
at low cost and small size, the decoupling scheme shown
below could be implemented.
+5V
RELAY
SW+
SW-
SWC
0.22μ 0.22μ
VBL VBH
HC5518X
FIGURE 12. ALTERNATE DECOUPLING SCHEME
It is important to place the external diode between the VBH
pin and the decoupling capacitor. Attaching the decoupling
capacitor directly to the VBH pin will degrade the reliability of
the device. Refer to Figure 12 for the proper arrangement.
This applies to both single and stacked and decoupling
arrangements.
If VBL and VBH are tied together to override the battery
switch function, then the external diode is not needed and
the decoupling may be attached directly to VBH.
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.
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.
FIGURE 13. EXTERNAL RELAY SWITCHING
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 in Figure 14.
TIP
RING
TEST
LOAD
SW+
SW-
SWC
FIGURE 14. 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.
16
FN4831.14
December 18, 2006