Table 2.
Z
T
= 510
(
Z
2WIN
– 2R
F
)
User-Programmable Components
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 V
RX
to the RSN pin, Z
T
is defined
above, and G
42L
is the desired receive gain.
R
DC1
, R
DC2
, and C
DC
form the network connected to the
RDC pin. R
DC1
and R
DC2
are approximately equal.
Z
L
1000
•
Z
T
-
Z
RX
=
----------
•
-------------------------------------------------
G
42L
Z
T
+ 510
(
Z
L
+ 2R
F
)
2500
-
R
DCI
+ R
DC2
=
------------
I
FEED
R
DC1
+ R
DC2
-
C
DC
= 1.5 ms
•
-------------------------------
R
DC1
•
R
DC2
365
-
R
D
=
--------
,
I
T
Z
M
0.5 ms
-
C
D
=
----------------
R
D
R
D
and C
D
form the network connected from RD to –5 V and
I
T
is the threshold current between on hook and off hook.
Z
M
is connected from V
MG
(metering source) to the RSN pin,
V
M2W
is the desired magnitude of the metering signal at the
2-wire output (usually 2.2 Vrms) and K
1
(
ω
) is defined below.
V
MG
K
1
( ω ) •
Z
L
•
Z
T
-
-
=
--------------
•
------------------------------------------------------------------------
V
M2W
Z
T
+ 0.51
•
K
1
( ω ) (
2R
F
+ Z
L
)
1000
-
K
1
( ω )
=
-------------------------------------------------------------------------------------------------------------
–9
1 + j
ω (
11.5
•
10 + CX
⁄
2
) (
36 + Z
L
+ 2R
F
)
where: CX = The values of the identical capacitors from
A and B to GND
ω
= 2
π •
metering frequency
12
Am79M535 Data Sheet
AMD [ ADVANCED MICRO DEVICES ]
