HC55171_03 Datasheet, PDF (7/20 Pages) Intersil Corporation – 5 REN Ringing SLIC for ISDN Modem/TA and WLL

Functional Diagram
HC55171
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
16
RING
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
provided 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
operating 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
transmission and supervisory functions.
7
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.