HC55171 Datasheet, PDF (5/18 Pages) Intersil Corporation – 5 REN Ringing SLIC for ISDN Modem/TA and WLL

HC55171
Functional Diagram
R
TF
25
TF
+^-
14
TIP
SENSE
R
R
R
R
4.5K
R
R
R/2
R/20
2R
V_RX
17
OUT 1
12
+2V
-IN 1
13
V_RING
24
+^- OP AMP
+^{- TA}
2R
SHD
15
RING
SENSE 1
RING ¹⁶
SENSE 2
100K
100K
100K
100K
4.5K
25K
RA
+^-
25K
90K
90K
RTD
FAULT
DET
RF
26
RF _+-
90K
VB/2
REF
GM
+^-
R = 108kΩ
3
V_REF
18
NU
28
RTI
V_TX
19
V_CC
AGND
2
BIAS
NETWORK
1
22
BGND
27 _VBAT
THERM
LTD
SH
TSD
4
F1
5
F0
6
RS
9
TST
GK
RF2
11
I_LMT
RFC
20
RDI
7
SHD
8
RTD
10
ALM
21
RDO
HC55171 DEVICE TRUTH TABLE
F1
F0
STATE
0
0
Loop power Denial Active
0
1
Power Down Latch RESET, Power on
RESET
1
0
RD Active
1
1
Normal Loop feed
The truth table for the internal logic of the HC55171 is pro-
vided in the above table. This family of ringing SLICS can be
configured to support traditional unbalanced ringing and thru
SLIC balanced ringing. Refer to the HC5509A1R3060 for
unbalanced ringing application information. The device oper-
ating states used by thru SLIC ringing applications are loop
power denial and normal feed. During loop power denial, the
tip and ring amplifiers are disabled (high impedance) and the
DC voltage of each amplifier approaches ground. The SLIC
will not provide current to the subscriber loop during this mode
and will not detect loop closure. Voice transmission occurs
during the normal loop feed mode. During normal loop feed
the SLIC is completely operational and performs all transmis-
sion and supervisory functions.
Power Dissipation
Careful thermal design is required to guarantee that the
maximum junction temperature of 150^oC of the device is not
exceeded. The junction temperature of the SLIC can be cal-
culated using:
T_J = T_A + θ_JA(I_CC V_CC + I_BAT V_BAT – ((I_LOOP)² • R_LOOP))
(EQ. 1)
Where T_A is maximum ambient temperature and θ_JA is junc-
tion to air thermal resistance (and is package dependent).
The entire term in parentheses yields the SLIC power dissi-
pation. The power dissipation of the subscriber loop does
not contribute to device junction temperature and is sub-
tracted from the power dissipation term. Operating at 85^oC,
the maximum PLCC SLIC power dissipation is 1.18W. Like-
wise, the maximum SOIC SLIC power dissipation is 0.92W.
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