hc5523 Intersil Corporation, hc5523 Datasheet - Page 8

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

Electrical Specifications
Circuit Operation and Design Information
The HC5523 is a current feed voltage sense Subscriber Line
Interface Circuit (SLIC). This means that for short loop
applications the SLIC provides a programed constant current to
the tip and ring terminals while sensing the tip to ring voltage.
The following discussion separates the SLIC’s operation into
its DC and AC paths, then follows up with additional circuit
and design information.
Constant Loop Current (DC) Path
SLIC in the Active Mode
The DC path establishes a constant loop current that flows
out of tip and into the ring terminal. The loop current is
programmed by resistors R
the R
the voltage across R
constant current feed conditions, the voltage drop across R
sets the R
flows through R
establishes a current (I
+R
current circuit, to become the tip and ring loop currents.
For the purpose of the following discussion, the saturation
guard voltage is defined as the maximum tip to ring voltage
at which the SLIC can provide a constant current for a given
battery and overhead voltage.
Active State (C1, 2 = 0, 1)
On-Hook
PSRR
V
V
V
CC
EE
BAT
DC2
to 2 or 4-Wire Port
to 2 or 4-Wire Port
DC
to 2 or 4-Wire Port
). This current is then multiplied by 1000, in the loop
pin (Figure 13). The R
DC
voltage to -2.5V. This occurs when current
1
PARAMETER
into the current source I
1
in the saturation guard circuit. Under
RSN
DC1
) that is equal to V
8
DC
, R
T
R
number references in the figures refer to the 28 lead PLCC package. (Continued)
-48V SUPPLY
+5V SUPPLY
A
D
-5V SUPPLY
R
600Ω
DC2
= -40
voltage is determined by
= 39kΩ, R
L
o
and the voltage on
C to 85
2
FIGURE 12. POWER SUPPLY REJECTION RATIO
. The R
SG
I
I
I
(Note 30, Figure 12)
(Note 30, Figure 12)
(Note 30, Figure 12)
RDC
CC
EE
BAT
o
= 0Ω, R
C, V
TIP
27
RING
28
DC
/(R
CC
voltage
DC1
F1
= +5V ±5%, V
RSN
= R
V
100mV
19
16
TX
CONDITIONS
F2
1
HC5523
= 0Ω, C
RMS
600kΩ
R
300kΩ
EE
T
, 50Hz TO 4kHz
R
RX
HP
= -5V ±5%, V
For loop resistances that result in a tip to ring voltage less
than the saturation guard voltage the loop current is defined
as:
where: I
R
Capacitor C
signals from the battery feed control loop. The value of C
is determined by Equation 2:
where T = 30ms
NOTE: The minimum C
Figure 14 illustrates the relationship between the tip to ring
voltage and the loop resistance. For a 0Ω loop resistance both
tip and ring are at V
so does the voltage differential between tip and ring. When
this differential voltage becomes equal to the saturation guard
voltage, the operation of the SLIC’s loop feed changes from a
constant current feed to a resistive feed. The loop current in
the resistive feed region is no longer constant but varies as a
function of the loop resistance.
I
C
L
= 10nF, C
DC1
DC
=
------------------------------------- -
R
V
=
TX
and R
DC1
T
L
PSRR = 20 log (V
2.5V
×
BAT
DC
= Constant loop current.
+


DC
---------------
R
DC2
R
= 1.5µF, Z
DC1
= -48V, AGND = BGND = 0V, R
DC2
1
between R
= Loop current programming resistors.
+
×
BAT
---------------
R
MIN
1000
DC2
-
-
-
-
-
-
DC
L
1
= 600Ω, Unless Otherwise Specified. All pin
T X
/2. As the loop resistance increases,
value is obtained if R


/V
DC1
IN
)
TYP
and R
3.7
1.1
2.2
40
40
40
DC2
DC1
MAX
removes the VF
5.8
1.8
3.7
DC1
-
-
-
= R
DC2
= R
DC2
= 41.2kΩ,
UNITS
mA
mA
mA
dB
dB
dB
(EQ. 1)
(EQ. 2)
DC