le79555 Zarlink Semiconductor, le79555 Datasheet - Page 12

• Manufacturer Part Number: le79555
• Description: Subscriber Line Interface Circuit
• Manufacturer: Zarlink Semiconductor

Note:
Ring ground detection in Tip Open is automatic. If longitudinal current is greater than IGK in Active, Standby, or Tip Open, the DET will go low.
Therefore, if in Active or Standby, DET may be an indication of off hook, ground fault, or both.
Table 1. SLIC Device Decoding
Table 2. User-Programmable Components
(I
Z
Z
R
C
I
C
I
T
STANDBY
Threshold on to off hook
T
RX
DC1
DC
CAS
OFF
=
=
State
=
=
250 Z
+
0
1
2
3
4
5
6
7
=
------------ - •
G
R
1.5 ms
414
--------- - ,
Z
R
42L
------------------------------------------ -
170 kΩ 2π f
DC2
(
L
D
=
2WIN
------------------------------- -
400 Ω
V
=
•
BAT
--------------------------------------------------- -
Z
1
---------------
I
R
---------------------------------- -
T
R
•
–
LOOP
) (I
625
+
DC1
DC1
2R
–
250 Z
C3
+
I
Threshold off to on hook
0
0
0
0
1
1
1
1
T
3 V
F
•
500Z
R
ON
+
•
)
L
c
(
R
R
=
DC2
DC2
L
T
368
--------- - ,
R
+
D
2R
C2
0
0
1
1
0
0
1
1
F
)
C
D
)
=
Zarlink Semiconductor Inc.
0.5 ms
------------------ -
C1
0
1
0
1
0
1
0
1
R
D
12
Reserved
Reserved
Active Reverse Polarity (-1, 2 devices)
Tip Open
Open Circuit
Ringing
Active
Standby
Z
R
computing Z
capacitance between VTX and RSN must be taken into account.
Z
desired receive gain. Z
R
and R
the constant-current region.
R
is the threshold current between on-hook and
off-hook.
C
frequency.
Standby loop current (resistive region).
T
RX
F
DC1
D
CAS
, and Z
is connected between the VTX and RSN pins. The fuse resistors are
and C
is connected from VRX to RSN. Z
, R
DC2
is the regulator filter capacitor and f
DC2
D
2WIN
are approximately equal. I
form the network connected from R
, and C
Two-Wire Status
T
, the internal current amplifier pole and any external stray
is the desired 2-wire AC input impedance. When
DC
form the network connected to the R
L
= Load Impedance, AD to BD.
LOOP
T
is defined above, and G
c
is the desired loop current in
is the desired filter cut-off
X
X
Loop detector
Ring Ground (see note)
Ring trip
Ring trip
Loop detector
Loop detector
D
to AGND/DGND and I
DET Output
DC
pin. R
42L
is the
DC1
T