HC55171B Datasheet, PDF (5/11 Pages) Intersil Corporation – Low Cost 5 REN Ringing SLIC for ISDN Modem/TA and WL

HC55171B
R
TF
25
TF
+^-
TIP
14
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
16
RING
SENSE 2
100K
100K
100K
100K
4.5K
25K
RA
+^-
25K
90K
90K
RTD
FAULT
DET
26
RF
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_LIMIT
RFC
20
RDI
7
SHD
8
RTD
10
ALM
21
RDO
HC55171B 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 (unbalanced ringing)
1
1
Normal Loop feed
The truth table for the internal logic of the HC55171B is
provided in the above table. This family of ringing SLICs can be
configured to support traditional unbalanced ringing and
through SLIC balanced ringing. The device operating states
used by through 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 volt-
age 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 transmission 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
calculated 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
junction to air thermal resistance (and is package
dependent). The entire term in parentheses yields the SLIC
power dissipation. The power dissipation of the subscriber
loop does not contribute to device junction temperature and
is subtracted from the power dissipation term. Operating at
85^oC, the maximum PLCC SLIC power dissipation is 1.18W.
Likewise, the maximum SOIC SLIC power dissipation is
0.92W.
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