- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄385479 > LM2893M (NATIONAL SEMICONDUCTOR CORP) LM1893/LM2893 Carrier-Current Transceiver PDF資料下載
參數(shù)資料
| 型號： | LM2893M |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 通信及網(wǎng)絡(luò) |
| 英文描述： | LM1893/LM2893 Carrier-Current Transceiver |
| 中文描述： | SPECIALTY TELECOM CIRCUIT, PDSO20 |
| 封裝： | 0.300 INCH, PLASTIC, SOP-20 |
| 文件頁數(shù)： | 17/24頁 |
| 文件大?。?/td> | 576K |
| 代理商： | LM2893M |
The Coupling Transformer
(Continued)
TL/H/6750–32
FIGURE 29. Impressed line voltage for a given Z
L
for each of the 3 taps available
on the recommended transformers
P
O
e
I
O
V
O
e
I
OPP
2
0
2
D
2(
b
V
ALC
a
V
a
)
2
0
2
(
e
(
b
4.7
a
V
a
)I
O
4
(5)
where I
O
is in amps peak-to-peak at an elevated T
J
P
O
e
(18
b
4.7) 0.06
4
R
Q
ll l
Z
LN
l
ê
e
V
O2
P
O
R
Q
is found using Z
LN
and the value for N found when as-
suming Q
U
e
35.
l
Z
LN
l
ê
e
N
2
Z
LN
e
(7.07)
2
13.9
e
695
X
1
e
e
0.200 W
e
(
b
V
ALC
a
V
a
)
0
2
(6)
I
O
e
442
X
(7)
(8)
R
Q
e
1
R
Q
ll l
Z
LN
l
ê
R
Q
1
a
Q
U2
e
b
1
l
Z
LN
l
ê
1210
1
a
35
2
e
1
X
1
1
442
b
1
695
e
1210
X
(9)
R
QS
e
(10)
Only Q
L
remains to be found to calculate L
1
. Q
L
is related to
the
b
3 dB (half-power) bandwidth by
1
Q
L
e
BW (% of F
O
)
An iterative solution is forced where line pull,
D
F
Q
, must be
guessed to find Q
L
and L
1
. L
1
is then used to check the line
pull guess; a large error requires a new guess. Try a BW of
8.7% - that is 4.4% for deviation, 1% for TC of F
O
, and
3.3% for
D
F
Q
- giving Q
L
e
11.5.
442
2
q
c
125 000
c
11.5
Knowing the core inductance per turn, L, and L
1
, the num-
ber of turns is found.
(11)
L
1
e
T
1
e
0
e
49.0
m
H
(12)
L
1
L
e
49.0
m
H
20 nH/T
e
49
(/2
turns
(13)
T is normally an integer, but these transformers require so
few turns that half-turns are specified, remembering that the
remaining
(/2
turn is completed on the P.C. board and is
loosely coupled. The secondary turns are calculated
T
2
e
T
1
N
e
49.5
7.07
e
7.00
e
7 turns
(15)
giving an L
2
of 0.98
m
H. Note that the recommended 125
kHz transformer mirrors these specifications. The resonat-
ing capacitor is
C
Q
e
1
(2
q
F
Q
)
2
L
1
e
33.1
c
10
b
9
e
33 nF
(16)
Line pull
D
F
Q
was calculated (reference 3) for a Z
L
magni-
tude of 14
X
and up with any phase angle from
b
90
§
to 90
§
.
D
F
Q
was 6.4% - well above the 3.3% estimate. Referring to
(11), an 11.8% bandwidth is required, forcing L
1
to be re-
duced to reduce Q. That fix was not implemented; some
signal attenuation under worst-case drift and
D
F
Q
is al-
lowed. L
1
is already so small that the 31 gauge winding
conducts a
(/4
A
RMS
circulating current.
Line Carrier Detection
While the addition of a carrier detection circuit (for a mute or
squelch function) will only decrease receiver ultimate sensi-
tivity, there is sometimes good reason to employ it to free
the controller from watching for RX signal when no carrier is
incoming, or to employ it to reduce the probability of line
collisions (when multiple transmitters operate simultaneous-
ly to cause one or more transmissions to fail). Unless the
detector is heavily filtered or uses a high carrier amplitude
threshold, there will be false outputs that force the controller
to have Data Out data checking capability just as is required
when using no carrier detector. If false triggering is mini-
mized, the probability of line collisions is increased due to
the inability to sense low carrier amplitudes and because of
sense delay. The property of the LM1893 to change output
state infrequently (although the polarity is undefined) when
in the RX mode, with no incoming carrier, reduces the desire
to implement carrier detection and preserves the full ulti-
mate sensitivity. Also, many impulse-noise insensitive trans-
mission schemes, like handshaking, are easily modified to
recover from line collisions.
Regarding this, it should be stated that for very complicated
industrial systems with long signal runs and high line noise
levels, it is probably wise to use a protocol which is inherent-
ly collision free so that no carrier detect hardware or soft-
ware is needed. A token passing protocol is an example of
such a system.
Figure 30 shows a low cost carrier amplitude detection cir-
cuit.
Audio Transmission
The LM1893 is designed to allow analog data transmission
and reception. Base-band audio-bandwidth signals FM
modulate the carrier passing through the tuned transformer
(placing a limit on the usable percent modulation) onto the
power line to be linearly demodulated by the receiver PLL.
Because the receiver data path beyond the phase detector
will pass only digital signal, external audio filtering and am-
plification is required.Figure 31 shows a simple audio trans-
mitter and receiver circuit utilizing a carrier detection mute
circuit. A single LM339 quad. comparator may be used to
build the carrier detect and mute. Filter bandwidth is held to
a minimum to minimize noise, especially line-related corre-
lated noise.
Communication and System
Protocols
The development of communication and system protocols
has historically been the single most time consuming ele-
ment in design of carrier current systems. The protocols are
defined as the following:
1.Communication protocol: a software method of encoding
and decoding data that remains constant for every transmis-
17
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM2893N | LM1893/LM2893 Carrier-Current Transceiver |
| LM2895 | AUDIO POWE RAMPLIFIER |
| LM1895 | AUDIO POWE RAMPLIFIER |
| LM1895N | AUDIO POWE RAMPLIFIER |
| LM2895P | AUDIO POWE RAMPLIFIER |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM2893MX | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| LM2893N | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| LM28A WAF | 制造商:Texas Instruments 功能描述: |
| LM28SM2.5 | 制造商:Texas Instruments 功能描述: |
| LM28W | 制造商:BEAVERSWOOD 功能描述:MARKER MAG WHITE 20X80MM PK100 制造商:BEAVERSWOOD 功能描述:MARKER, MAG, WHITE, 20X80MM, PK100 |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。