
10
Am79R79 Data Sheet
Notes:
1. Unless otherwise noted, test conditions are BAT1 =
–
75 V, BAT2 =
–
24 V, V
CC
= +5 V, V
NEG
=
–
5 V, R
L
= 600
,
R
DC1
= 80 k
, R
DC2
= 20 k
, R
D
= 75 k
, no fuse resistors, C
HP
= 0.018 μF, C
DC
= 1.2 μF, D
1
= D
2
= 1N400x,
two-wire AC input impedance (ZSL) is a 600
resistance synthesized by the programming network shown below.
R
SGL
= open, R
SGH
= open, R
DCR
= 2 k
, R
RT1
= 430 k
, R
RT2
= 12 k
, C
RT
= 1.5 μF, R
SLEW
= 100 k
, C
SLEW
= 0.33 μF.
2. a. Overload level is defined when THD = 1%.
b. Overload level is defined when THD = 1.5%.
3. Balance return signal is the signal generated at V
TX
by V
RX
. This specification assumes that the two-wire AC load impedance
matches the programmed impedance.
4. Not tested in production. This parameter is guaranteed by characterization or correlation to other tests.
5. This parameter is tested at 1 kHz in production. Performance at other frequencies is guaranteed by characterization.
6. Group delay can be greatly reduced by using a Z
T
network such as that shown in Note 1 above. The network reduces the
group delay to less than 2 μs and increases 2WRL. The effect of group delay on linecard performance may also be compensated
for by synthesizing complex impedance with the QSLAC or DSLAC device.
7. 70 Vpk provides 50 Vrms with a crest factor of 1.25 to a load of 1400
with 2
Rf = 100, and Rline = 70
(1570
).
8. Open Circuit V
AB
can be modified using RSGH.
9. R
D
must be greater than 56 k
. Refer to Table 2 for typical value of R
LTH
.
10. Lower power is achieved by switching into low-battery state in standby. Standby loop current is returned to V
BAT1
regardless
of the battery selected.
Notes:
* Only
–
1 and
–
2 performance grade devices support polarity reversal.
** For correct ground-start operation using Tip Open, V
BAT1
on-hook battery must be used.
Table 1. SLIC Decoding
(DET) Output
State
C3 C2 C1
2-Wire Status
E1 = 1
E1 = 0
Battery Selection
0
0 0 0
Open Circuit
Ring trip
Ring trip
B2EN
1
0 0 1
Ringing
Ring trip
Ring trip
2
0 1 0
Active
Loop detector
Ground key
3
0 1 1
On-hook TX (OHT)
Loop detector
Ground key
4
1 0 0
Tip Open
Loop detector
Ground key
B2EN = 1**
5
1 0 1
Standby
Loop detector
Ground key
V
BAT1
6*
1 1 0
Active Polarity Reversal
Loop detector
Ground key
B2EN
7*
1 1 1
OHT Polarity Reversal
Loop detector
Ground key
RT2 = 150 k
CT1 = 60 pF
RT1 = 150 k
VTX
RSN
V
RX
RRX = 300 k
~