Le79555
Table 1. SLIC Device Decoding
State
0
1
2
3
4
5
6
7
Note:
C3
0
0
0
0
1
1
1
1
C2
0
0
1
1
0
0
1
1
C1
0
1
0
1
0
1
0
1
Reserved
Reserved
Active Reverse Polarity (-1, 2 devices)
Tip Open
Open Circuit
Ringing
Active
Standby
Two-Wire Status
X
X
Data Sheet
DET Output
Loop detector
Ring Ground (see note)
Ring trip
Ring trip
Loop detector
Loop detector
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 2. User-Programmable Components
Z
T
= 250
(
Z
2WIN
–
2R
F
)
Z
L
500Z
T
-
-
Z
RX
=
------------
•
---------------------------------------------------
G
42L
Z
T
+ 250
(
Z
L
+ 2R
F
)
625
R
DC1
+ R
DC2
= ---------------
I
LOOP
R
DC1
+ R
DC2
-
C
DC
=
1.5 ms
•
----------------------------------
R
DC1
•
R
DC2
I
T
OFF
Z
T
is connected between the VTX and RSN pins. The fuse resistors are
R
F
, and Z
2WIN
is the desired 2-wire AC input impedance. When
computing Z
T
, the internal current amplifier pole and any external stray
capacitance between VTX and RSN must be taken into account.
Z
RX
is connected from VRX to RSN. Z
T
is defined above, and G
42L
is the
desired receive gain. Z
L
= Load Impedance, AD to BD.
R
DC1
, R
DC2
, and C
DC
form the network connected to the R
DC
pin. R
DC1
and R
DC2
are approximately equal. I
LOOP
is the desired loop current in
the constant-current region.
414
=
---------
,
-
R
D
I
T
ON
368
= ---------
,
-
R
D
0.5 ms
C
D
= ------------------
R
D
and C
D
form the network connected from R
D
to AGND/DGND and I
T
-
R
D
is the threshold current between on-hook and
off-hook.
(I
Threshold on to off hook
) (I
Threshold off to on hook
)
1
-
C
CAS
= ------------------------------------------
170 kΩ
•
2π
•
f
c
V
BAT
–
3 V
-
I
STANDBY
= -------------------------------
400
Ω
+
R
L
C
CAS
is the regulator filter capacitor and f
c
is the desired filter cut-off
frequency.
Standby loop current (resistive region).
12
Zarlink Semiconductor Inc.
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
