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參數(shù)資料
| 型號： | LM2893M |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 通信及網(wǎng)絡 |
| 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)： | 8/24頁 |
| 文件大?。?/td> | 576K |
| 代理商： | LM2893M |
Application Information
(Continued)
Y
Recommended
Value
Purpose
Effect of making the component value:
Notes
Smaller
Larger
C
O
560 pF
R
O
6.2 k
X
Together, C
O
and R
O
Increases F
O
set ICO F
O
.
Decreases F
O
Decreases F
O
l
7.6 k not recommended. Poor F
O
TC with
k
5.6 k R
O
.
g
5% NPO ceramic. Use low TC
Increases F
O
k
5.6 k not recommended.
C
F
0.047
m
F
PLL loop filter pole
Less noise immune, higher More noise immune, lower Depending on R
F
value and
f
DATA
, more PLL stability.
f
DATA
, less PLL stability.
PLL less stable, allows
PLL more stable, allows
less C
F
. Less ringing.
more C
F
. More ringing.
Low TX line amplitude.
Drives lower line Z.
Less 60 Hz T
1
current.
More 60 Hz T
1
current.
Less stored charge.
More stored charge.
F
O
, PLL unstable with large
C
F
. See Apps. Info. C
F
and R
F
values not critical.
t
250 V non-polar. Use 2C
C
on hot and neutral for max.
line isolation, safety.
R
F
3.3 k
X
PLL loop filter zero
C
C
0.22
m
F
Couples F
O
to line,
C
C
and T
1
low-pass
attenuates 60 Hz.
C
Q
0.033
m
F
Tank matches line Z, Tank F
O
up or increase
bandpass filters,
L of T
1
for constant F
O
.
isolates from line,
Smaller L: higher F
O
or
and attenuates
increase C
C
; decreased F
O
decrease C
C
; increased F
O
pull with control of F
O
TC
transients.
line pull.
line pull.
Tank F
O
down or decrease 100 V nonpolar, low TC,
g
10%
L of T
1
for constant F
O
.
High large-signal Q needed.
Larger L: lower F
O
or
Optimize for low F
O
line
T
1
Use
recommended
XFMR
and Q.
C
A
0.1
m
F
R
A
10 k
X
C
L
0.047
m
F
ALC pole
ALC zero
Noise spikes turn ALC off.
Less stable ALC.
Slower ALC response.
More stable ALC.
R
A
optional. ALC stable
for C
A
t
100 pF.
Any reasonably low TC cap.
300 pF guarantees stability.
Limiter 50 kHz pole,
60 Hz rejection.
Higher pole F, more 60 Hz
reject. F
O
attenuation
Less noise immune, shorter More noise immune, longer Low leakage
g
20% cap.
V
OS
hold, faster V
OS
aqui-
V
OS
hold, slower V
OS
aqui- Scale with f
DATA
.
sition, shorter preamble.
sition, longer preamble.
Lower pole F, less 60 Hz
reject, more noise BW.
C
M
0.47
m
F
Holds RX path V
OS
C
I
0.047
m
F
Rejects short pulses Less impulse reject, less
like impulse noise.
delay, more pulse jitter.
More impulse reject, more
delay, less pulse jitter.
C
I
charge time
(/2
bit nom.
Must be
k
1 bit worst-case.
R
C
10 k
X
R
Z
12 k
X
Open-col. pull-up
Less available sink I.
Less available source I.
R
C
t
1.5 k
X
on 5.6 V
1
k
I
Z
k
30 mA recommended.
(Chip power-up needs 5.6 V)
5.6 V Zener bias
Larger shunt current,
more chip dissipation.
Smaller shunt current,
less V
a
current draw.
Z
T
t
44 V BV
k
60 V peak
Transient clamp
Z
T
failure, higher series
R-excess peak V, Zener
and chip damage,
less ruggedness.
Damage Z
T
, pull up V
a
.
Failure on Transient
Z
T
costly, lower series
R gives enhanced
transient clamp,
more ruggedness.
Excessive TX attenuation.
Costly
Recommend Zener rated
for
t
500 W for 1 ms.
R
T
4.7
X
D
T
t
44V BV
R
B
180
X
Q
B
Power NPN
R
G
1.1
X
C
B
t
47
m
F
Z
A
5.1V
Transient I limit
Over-drive Clamp
Carbon comp. recommended.
IRF 11DQ05 or 1N5819
Base bleed
Boost gain device
Current setting R
Faster, lower THD I
O
.
Excessive T
J
and V
SAT
.
More I
O
, need higher h
fe
.
Transients destroy chip.
Inadequate turn-off speed. Boost optional. Q
B
F(
b
3 dB)
More rugged, but costly.
of
l
200 MHz. R
B
l
24 Ohm.
Less I
O
, lower min. h
fe
.
I
O
e
70
[
(10
a
R
G
)/R
G
]
mApp.
Less supply spike.
V
a
never over abs. max.
Supply bypass
Stop ALC charge
in RX mode
Excess ALC
current flow
ALC RX charging
not inhibited over T
J
Z
A
optional - 5.1V
g
20% low leakage type
FIGURE 5. A quick explanation of the external component function using the circuit ofFigure 4. Values given are for V
a
e
18 V, F
O
e
125 kHz, f
DATA
e
360 Baud (180 Hz), using a 115 V 60 Hz power line
Component Selection
Assuming the circuit ofFigure 4 is used with something oth-
er than the nominal 125 kHz carrier frequency, 180 Hz data
rate, 18V supply voltage, etcetera, the component values
listed in Figure 5 will need changing. This section will help
direct the CCT designer in finding the required component
values with emphasis placed on look-up tables and charts. It
is assumed that the designer has selected values for carrier
center frequency, F
O
; data rate, f
DATA
; supply voltage, V
a
;
power line voltage, V
L
; and power line frequency, F
L
. If one
or more of those parameters is not defined, one may read
the data sheet and make an educated guess.
Maxims to keep in mind, based on CCT electrical perform-
ance considerations only, are: 1) the higher the F
O
the bet-
ter, 2) the lower the maximum data rate the better, and 3)
the more time and frequency filtering the better.
Use Figure 5 as a quick reference to the external compo-
nent function.
THE TRANSMITTER
C
O
Central to chip operation is the low TC of F
O
emitter-cou-
pled oscillator. With proper C
O
, the F
O
of the 2V
BE
ampli-
tude triangle-wave oscillator output may vary from near DC
to above 300 kHz. While C
O
may have any value, C
O
should
8
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