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| 型號： | HC-5502A |
| 廠商： | Intersil Corporation |
| 英文描述： | () |
| 中文描述： | （） |
| 文件頁數： | 1/3頁 |
| 文件大小： | 53K |
| 代理商： | HC-5502A |
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1-888-INTERSIL or 321-724-7143
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Copyright
Intersil Corporation 2000.
Using Ring Sync with HC-5502A and
HC-5504 SLICs
Introduction
The ring synchronization (sync) input pin is a TTL compati-
ble clock input in both the HC-5502A and HC-5504 SLICs.
It’s purpose is to insure that the ring relay is activated or
deactivated only when the instantaneous AC ring voltage,
which may be as high as 150V peak, is at or near AC zero
crossing.
If ring sync is not used, it must be tied high to insure proper
ring trip. When used, it is important to consider at which zero
crossing of the AC ring voltage, positive or negative, the ring
sync signal must be synchronized with. Subsequent illustra-
tions and equations highlight this consideration.
For detailed description of the ring trip sequence of events,
refer to Application Note 549 by P. G. Phillips. Excerpts from
the pertinent section are included below.
Ring Trip Sequence
The Ring Command (RC) input is taken low during ringing.
This activates the ring relay driver (RD) output providing the
telephone is not off-hook or the line is not in a power denial
state. The ring relay connects the ring generator to the sub-
scriber loop. The ring generator output is usually an
80V
RMS
, 20Hz signal. For use with the Intersil SLIC, the ring
signal should not exceed 150V peak. Since the telephone
ringer is AC coupled, only ring current will flow. For the HC-
5502A SLIC, the ring current is sunk by the ring feed ampli-
fier output stage whereas for the HC-5504 the ring path
flows directly into V
B
- via a set of relay contacts. The high
impedance terminal RFS exists on the HC-5504 so that the
low impedance RF node can be isolated from the hot end of
the ring path in the battery referenced ring scheme.
The AC ring current flowing in the subscriber circuit will be
sensed across RB4, and will give rise to an AC voltage at the
output of the longitudinal amplifier. R19 and C4 attenuate
this signal before it reaches the ring trip detector to prevent
false ring trip. C4 is nominally set at 0.47
μ
F but can be
increased towards 1
μ
F for short lines or if several tele-
phones are connected in parallel across the line in order to
prevent false or intermittent ring trip.
When the subscriber goes off-hook, a DC path is established
between the output winding of the ring generator and the
battery ground or V
B
- terminal. A DC longitudinal imbalance
is established since no tip feed current is flowing through the
tip feed resistors. The longitudinal amplifier output is driven
negative. Once it exceeds the ring trip threshold of the ring
trip detector, the logic circuitry is driven by GK to trip the ring
relay establishing an off-hook condition such that SHD will
become active as loop metallic current starts to flow.
Figure 1 illustrates the sequence of events during ring trip
with ring synchronization. Note, that owing to the 90
o
phase
shift introduced by the low pass filter (R19, C4) the RS pulse
will occur at the most negative point of the attenuated ring
signal that is fed into the ring trip detector. Hence, when DC
conditions are established for RTD, the AC component actu-
ally assists ring trip taking place. If ring synchronization is
not used, then the RS pin should be held permanently to a
logic high of 5V nominally: ring trip will occur asynchronously
with respect to the ring voltage. Ring trip is guaranteed to
take place within three ring cycles after the telephone going
off-hook.
FIGURE 1. RING TRIP SEQUENCE
Application Note
January 1997
AN571.1
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| HC5502A3 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Telecommunication IC |
| HC5502A4P | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Telecommunication IC |
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| HC-5502B1 | 制造商:INTERSIL 制造商全稱:Intersil Corporation 功能描述:SLIC Subscriber Line Interface Circuit |
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