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參數(shù)資料
| 型號： | LM1893N |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 通信及網(wǎng)絡(luò) |
| 英文描述： | RES 250K-OHM 1% 0.125W THICK-FILM SMD-0805 5K/REEL-7IN-PA |
| 中文描述： | SPECIALTY TELECOM CIRCUIT, PDIP18 |
| 封裝： | PLASTIC, DIP-18 |
| 文件頁數(shù)： | 10/24頁 |
| 文件大?。?/td> | 576K |
| 代理商： | LM1893N |
Component Selection
(Continued)
C
C
Capacitor C
C
’s primary function is to block the power line
voltage from T
1
’s line-side winding. Also, C
C
and T
1
’s line-
side winding comprise a LC highpass filter. The self-induc-
tance of T
1
is far too low to support a direct line connection.
C
C
must have a low enough impedance at F
O
to allow T
1
to
drive transmitted energy onto the line. To drive a 14
X
power
line, the impedance of C
C
should be below 14
X
.
UseFigure 9 to find the reactive impedance of C
C
to check
that it is less than the line impedance. Then checkFigure 10
to see that the power line current is small enough to keep
T
1
well out of saturation; the recommended transformers
can withstand a 10 Amp-turn magnetizing force (1 Amp
through the worst-case 10 turn line-side winding).
Caution is required when choosing C
C
to avoid series reso-
nance of the series combination of C
C
, the transformer in-
ductance, and the reflected tank impedance. The low resist-
ance of the network under series resonance will load the
line, possibly decreasing range. For your particular line cou-
pling circuit, measure for series resonance using some ex-
pected line impedance load.
R
B
This base-bleed resistor turns Q
B
off quickly - important
since the amplifier output swing is about 200V/
m
s. An R
B
below about 24
X
will conduct excessive current and over-
load the chip amplifier and is not recommended.
TL/H/6750–11
FIGURE 9. C
C
’s impedance should be,
as a rule-of-thumb, smaller than the lowest
expected line impedance
R
G
This resistor, in parallel with the internal 10
X
resistor, fixes
the current gain of the output amplifier, and so the output
current amplitude. Figure 11 gives output current and mini-
mum AC current gain h
fe
for Q
B
when R
G
is used to boost
output current.
Q
B
The boost gain transistor Q
B
must be fast. Double-diffused
devices with 50 MHz F
T
’s work, slower transistors (epi-base
types) do not preserve a sinusoidal waveform when F
O
is
high or will cause the output amp. to oscillate. Q
B
must have
a certain minimum h
fe
for given boost levels, as shown in
Figure 11. Figure 12 shows the power Q
B
must dissipate
continuously operating with a shorted output. BV
CER
(R
e
R
B
) must be 60V or greater and Q
B
must have adequate
SOA for transient survival.
Z
T
Unfortunately, potentially damaging transient energy passes
through transformer T
1
onto the Carrier I/O pin (instanta-
neous power of greater than 1 kW has been measured us-
ing the recommended transformers). For self protection, the
Carrier I/O has an internal 44V voltage clamp with a 20
X
series resistance. A parallel low impedance 44V external
transient suppression diode will then conduct the lion’s
share of any current when transients force the Carrier I/O to
a high voltage.
TL/H/6750–12
FIGURE 10. The AC line-induced current passed by C
C
TL/H/6750–13
FIGURE 11. Output amplifier current and required min.
Q
B
h
fe
versus gain-setting resistor R
G
TL/H/6750–14
FIGURE 12. Boost transistor power dissipation versus
amplifier output current
Z
T
must be used unless some precaution is taken to protect
the Carrier I/O pin from line transients or transients caused
when stored line energy in C
C
is discharged by the random
phase of power line connection and disconnection. Worst
case, C
C
may discharge a full peak-to-peak line voltage into
the tuned circuit. Another way to reduce the need for Z
T
is
by placing another magnetic circuit in the signal path that
relies on a high, but easily saturated, permeability to couple
a primary and secondary winding - a toroidal transformer for
example. Toroids cost more than Z
T
.
Use an avalanche diode designed specifically for transient
suppression D they have orders of magnitude higher pulse
10
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM2893M | LM1893/LM2893 Carrier-Current Transceiver |
| LM2893N | LM1893/LM2893 Carrier-Current Transceiver |
| LM2895 | AUDIO POWE RAMPLIFIER |
| LM1895 | AUDIO POWE RAMPLIFIER |
| LM1895N | AUDIO POWE RAMPLIFIER |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| 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 |
| LM1894M | 制造商:Panasonic Industrial Company 功能描述:IC |
| LM1894M/NOPB | 功能描述:IC DYNAM NOISE REDUCT SYS 14SOIC RoHS:是 類別:集成電路 (IC) >> 線性 - 音頻處理 系列:- 其它有關(guān)文件:STA321 View All Specifications 標(biāo)準(zhǔn)包裝:1 系列:Sound Terminal™ 類型:音頻處理器 應(yīng)用:數(shù)字音頻 安裝類型:表面貼裝 封裝/外殼:64-LQFP 裸露焊盤 供應(yīng)商設(shè)備封裝:64-LQFP EP（10x10） 包裝:Digi-Reel® 其它名稱:497-11050-6 |
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