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參數(shù)資料
| 型號： | LM1893 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | LM1893/LM2893 Carrier-Current Transceiver |
| 中文描述： | LM1893/LM2893載波電流收發(fā)器 |
| 文件頁數(shù)： | 16/24頁 |
| 文件大?。?/td> | 576K |
| 代理商： | LM1893 |
Power Line Impedance
(Continued)
TL/H/6750–29
TL/H/6750–30
TL/H/6750–31
FIGURE 27. Complex-plane plots of measured 115V, 60 Hz line impedance where Z
L
e
R
L
a
jX
L
Power Line Attenuation
The wiring in most US buildings is a flat 3 conductor cable
called Amerflex, BX, or Romex. All referenced line imped-
ances refer to hot-to-neutral impedances with a grounded
center conductor. The cable has a 100
X
characteristic im-
pedance, a 125 kHz quarter-wavelength of 600 m (250 m at
300 kHz), and a measured 7 dB attenuation for a 50 m run
with a 10
X
termination. Generally, line loads may be treat-
ed as lumped impedances. Instrument line cords exhibit
about 0.7
m
H and 30 pF per meter.
Limited tests of CCT link range using this chip show exten-
sive coverage while remaining on one phase of a distribu-
tion transformer (100’s of m), with link failure often occuring
across transformer phases or through transformers unless
coupling networks are utilized. Total line attenuation allowed
from full signal to limiting sensitivity is more than 70 dB.
Typically, signal is coupled across transformer phases by
parasitic winding capacitance, typically giving 40 dB attenu-
ation between phased 115 V windings. Coupling capacitors
may be installed for improved link operation across phases.
Power factor correcting capacitor banks on industrial lines
or filter capacitors across the power lines of some electronic
gear short carrier signal and should be isolated with induc-
tors. Increasing range is sometimes accomplished by elect-
ing to install the isolating inductors (Figure 28) and coupling
capacitors, as well as by electing to use the boost option.
Frequency translating or time division multiplexed repeaters
will also increase range.
TL/H/6750–40
FIGURE 28. An isolation network to prevent: 1) noise
from some device from polluting the AC line, and 2) to
stop some low impedance device (measured at F
o
)
from shorting carrier signal. Component values given
as an example for F
o
e
125 kHz on
residential power lines
The Coupling Transformer
The design arrived at for T
1
is the result of an unhappy
compromise - but a workable one. The goals of 1) building
T
1
with a stable resonant frequency, F
Q
, that is little affect-
ed by the de-tuning effect of the line impedance Z
L
, and of
2) building a tightly line-coupled transformer for transmitted
carrier with loose coupling for transients, are somewhat mu-
tually exclusive. The tradeoffs are exposed in the following
example for the CCT designer attempting a new boost-ca-
pable, or different core, transformer design.
The compromises are eased by separating the TX output
and RX input in the LM2893. An untuned TX coupling trans-
former with only core coupling (not air-coupled solenoid
windings) would employ a high permeability, high magnetic
field, low loss, square saturating, toroidal core. The reso-
nant RX path would be isolated from line-pull problems by a
unilateral amplifier that operates at line voltages with much
more than 110 dB of dynamic range, or by a capacitively
coupled pulse transformer driving a unilateral amplifier and
filter, for increased selectivity. See the LM2893-specific ap-
plications section.
For a LM1893-style transformer application, first, choose
the turns ratio N based on an estimated lowest Z
L
likely
encountered, Z
LN
. Figure 29 shows graphically how N af-
fects line signal. N should be as large as possible to drive
Z
LN
with full signal. If T
1
has an unloaded Q, Q
U
, of well less
than 35, a guess of N somewhat high should be used and
later checked for accuracy. The recommended transformers
have secondary taps giving a choice of N
e
7.07, 10, and
14.1 (nominally) for driving Z
’s of 14, 7.0, and 3.5
X
re-
spectively (at T
J
e
25
§
C, V
a e
18V, and Q
U
e
35).
The resonating inductance of the tuned primary, L
1
, is
sought. Note that, while standard transformer design gives a
transformer self-inductance with an impedance at operating
frequency well above load impedance, the tuned transform-
er requires a low L
1
for adequate Q
U
and minimum line pull.
Result: relatively poor mutual coupling.
L
1
e
R
2
q
F
O
Q
(3)
It is known that resonant frequency F
Q
e
F
O
and some
minimum bandwidth, or maximum Q, will be required to pass
signal under full load conditions.
L
1
e
R
Q
ll l
Z
LN
l
ê
2
q
F
O
Q
L
l
Z
LN
l
ê
is the reflected Z
LN
, Q
L
is the loaded Q, and parallel
resistance R
Q
models all transformer losses and sets Q
O
.
R
Q
ll l
Z
LN
l
ê
is found knowing that it absorbs full rated power.
(4)
16
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| LM1893N | RES 250K-OHM 1% 0.125W THICK-FILM SMD-0805 5K/REEL-7IN-PA |
| LM2893M | LM1893/LM2893 Carrier-Current Transceiver |
| LM2893N | LM1893/LM2893 Carrier-Current Transceiver |
| LM2895 | AUDIO POWE RAMPLIFIER |
| LM1895 | AUDIO POWE RAMPLIFIER |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM1893 WAF | 制造商:Texas Instruments 功能描述: |
| LM1893N | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:LM1893/LM2893 Carrier-Current Transceiver |
| LM1893N/A+ | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Carrier/Multi-Wire Interface |
| LM1893N/B+ | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Carrier/Multi-Wire Interface |
| LM1894 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Dynamic Noise Reduction System DNR |
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