HC55120CM INTERSIL [Intersil Corporation], HC55120CM Datasheet - Page 13

• Manufacturer Part Number: HC55120CM
• Description: Low Power Universal SLIC Family
• Manufacturer: INTERSIL [Intersil Corporation]

The UniSLIC14 family of SLICs are voltage feed current
sense Subscriber Line Interface Circuits (SLIC). For short
loop applications, the voltage between the tip and ring
terminals varies to maintain a constant loop current. For long
loop applications, the voltage between the tip and ring
terminals are relatively constant and the loop current varies
in proportion to the load.
The tip and ring voltages for various loop resistances are
shown in Figure 13. The tip voltage remains relatively
constant as the ring voltage moves to limit the loop current
for short loops.
The loop current for various loop resistances are shown in
Figure 14. For short loops, the loop current is limited to the
programmed current limit, set by RILIM. For long loop
applications, the loop current varies in accordance with
Ohms law for the given tip to ring voltage and the loop
resistance.
HC55120, HC55121, HC55130, HC55131, HC55140, HC55141, HC55142, HC55143, HC55150, HC55151
23. Four-Wire to Two-Wire Gain Tracking - The 4-wire to 2-wire
24. Two-Wire Idle Channel Noise - The 2-wire idle channel noise
25. Four-Wire Idle Channel Noise - The 4-wire idle channel noise
FIGURE 13. TIP AND RING VOLTAGES vs LOOP RESISTANCE
-10
-15
-20
-25
-30
-35
-40
-45
-50
gain tracking is referenced to measurements taken for
E
R
G
or -55dBm to -40dBm and compare to -10dBm reading.
V
the 4-wire receive port and referenced to a 600 impedance level.
at V
and with the 4-wire receive port (VTX) floating (Reference
Figure 9).
at V
The noise specification is with respect to a 600 impedance
level at V
Figure 9).
-5
0
RX
L
TR
4-2
= 600 and is computed using the following equation:
TR
TX
, R
= -10dBm, 1.0kHz signal, E
CONSTANT
LOOP CURRENT
200
REGION
= 20 log (V
L
is specified with the 2-wire port terminated in 600 (R
is specified with the 2-wire port terminated in 600 (R
TIP
and E
TX
600 1000 1400 1800 2000
. The 4-wire receive port (VTX) floating (Reference
RING
RX
are defined in Figure 8. The level is specified at
TR
Circuit Operation and Design Information
/E
LOOP RESISTANCE ( )
RX
4-13
) vary amplitude -40dBm to +3dBm,
G
CONSTANT TIP TO RING
source removed from circuit,
VOLTAGE REGION
VBH = -48V
RD = 41.2k
ROH = 38.3k
RDC_RAC = 19.6k
RILim = 33.2k
4K
6K
8K
-44.5V
-2.5V
10K
L
L
)
).
26. Harmonic Distortion (2-Wire to 4-Wire) - The harmonic
27. Harmonic Distortion (4-Wire to 2-Wire) - The harmonic
28. Constant Loop Current - The constant loop current is
29. Ground Key Detector - (TRIGGER) Ground the Ring pin
30. Electrical Test - Not tested in production at -40
.
The following discussion separates the SLIC’s operation into
its DC and AC paths, then follows up with additional circuit
and design information.
DC Feed Curve
The DC feed curve for the UniSLIC14 family is user
programmable. The user defines the on hook and off hook
overhead voltages (including the overhead voltage for off
hook pulse metering if applicable), the maximum and
minimum loop current limits, the switch hook detect
threshold and the battery voltage. From these requirements,
the DC feed curve is customized for optimum operation in
any given application. An Excel spread sheet to calculate the
external components can be downloaded off our web site
www.intersil.com/telecom/unislic14.xls.
distortion is measured within the voice band with the following
conditions. E
taken at V
distortion is measured within the voice band with the following
conditions. E
3.4kHz, R
Figure 8).
calculated using the following equation:
I
through a 2.5k resistor and verify that GKD goes low.
(RESET) Disconnect the Ring pin and verify that GKD goes
high.
(Hysteresis) Compare difference between trigger and reset.
L
35
30
25
20
15
10
FIGURE 14. LOOP CURRENT vs LOOP RESISTANCE
5
0
= 1000/R
200
CONSTANT
LOOP CURRENT
REGION
L
TX
600
= 600 . Measurement taken at V
LIM
. (Reference Figure 7).
G
RX
= 0dBm at 1kHz, R
= V
= 0dBm0. Vary frequency between 300Hz and
1K
TR
/600 (Reference Figure 10).
1.4K 1.8K 2.2K 2.6K
LOOP RESISTANCE ( )
VBH = -48V
RD = 41.2k
ROH = 38.3k
RDC_RAC = 19.6k
RILim = 33.2k
CONSTANT TIP TO RING
VOLTAGE REGION
L
= 600 . Measurement
TR
3.0K 3.4K
. (Reference
o
C.
3.8K