hc5523 Intersil Corporation, hc5523 Datasheet - Page 10

• Manufacturer Part Number: hc5523
• Description: Lssgr/tr57 Co/loop Carrier Slic With Low Power Standby
• Manufacturer: Intersil Corporation

The value of R
loop length operation. This requires that the saturation guard
reference voltage be set as high as possible without clipping
the incoming or outgoing VF signal. A voltage margin of -4V
on tip and -4V on ring, for a total of -8V margin, is
recommended as a general guideline. The value of R
calculated using Equation 6:
where:
V
V
allow a maximum overload level of 3.1V peak.
For on-hook transmission R
SLIC in the Standby Mode
Overall system power is saved by configuring the SLIC in the
standby state when not in use. In the standby state the tip and
ring amplifiers are disabled and internal resistors are connected
between tip to ground and ring to V
enables a loop current to flow when the phone goes off-hook.
The loop current detector then detects this current and the SLIC
is configured in the active mode for voice transmission. The
loop current in standby state is calculated as follows:
where:
I
R
V
R
R
L
I
L
BAT
MAR
L
BAT
SG
SG
= Loop current in the standby state.
≈
= Loop resistance.
------------------------------- -
R
=
V
=
= Battery voltage.
L
= Battery voltage.
V







BAT
= Voltage Margin. Recommended value of -8V to
--------------------------------------------------------------------------------------------------------------------------------------------- - 17300
(
+
TR
----------------------------------------------------------------- - 17300
V
V
1800Ω
BAT
BAT
+
–
-
3V
–
Z
–
SG
V
L
5 10
V
MAR
MAR
•
+
-
E
should be calculated to allow maximum
G
Z
TR
)
5
×
–
RING
TIP



16.66V
1
5 10
+
•
(
--------------------------------------------- -
L
R
10
DC1
= ∞, Equation 6 reduces to:
R
R
5
I
I
–
M
M
F
F
600R L
+
BAT
V
R
TX
+
-
DC2
. This connection
FIGURE 16. SIMPLIFIED AC TRANSMISSION CIRCUIT
)



–
HC5523
16.66V
–
SG
+
-
(EQ. 6)
(EQ. 7)
(EQ. 8)
1







is
HC5523
A = 250
A = 250
(AC) Transmission Path
SLIC in the Active Mode
Figure 16 shows a simplified AC transmission model. Circuit
analysis yields the following design equations:
where:
V
including the voltage drop across the fuse resistors R
V
referenced 4-wire side or the SLIC tip and ring terminals.
I
R
Z
V
Z
E
Z
(AC) 2-Wire Impedance
The AC 2-wire impedance (Z
into the SLIC, including the fuse resistors, and is calculated
as follows:
Let V
V
V
---------- -
V
M
V
Z
T
RX
L
TR
TX
RX
G
TR
TR
F
TX
TX
T
= Is the AC metallic current.
= Is the line impedance.
= Is used to set the SLIC’s 2-wire impedance.
= Is a fuse resistor.
= Is the AC open circuit voltage.
+
= Is the AC metallic voltage. Either at the ground
= Is the AC metallic voltage between tip and ring,
= Is the analog ground referenced receive signal.
= Is used to set the 4-wire to 2-wire gain.
=
=
RX
=
V
-----------
Z
V
E
RX
RX
Z
TX
G
= 0. Then from Equation 10
T
–
•
=
+
I
------------ -
1000
M
I
I
------------ -
1000
M
M
I
•
M
•
Z
2R
L
A = 4
F
TR
V
RSN
TX
1000
) is the impedance looking
I
M
Z
T
Z
RX
V
TX
+
-
V
RX
(EQ. 10)
(EQ. 11)
(EQ. 12)
+
-
F
(EQ. 9)
.