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參數(shù)資料
| 型號(hào)： | DM74LS123SJX |
| 廠商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分類： | 諧振器 |
| 英文描述： | Monostable Multivibrator |
| 中文描述： | LS SERIES, DUAL MONOSTABLE MULTIVIBRATOR, PDSO16 |
| 封裝： | 5.30 MM, EIAJ TYPE2, SOP-16 |
| 文件頁數(shù)： | 2/8頁 |
| 文件大小： | 96K |
| 代理商： | DM74LS123SJX |
www.fairchildsemi.com
2
D
Functional Description
The basic output pulse width is determined by selection of
an external resistor (R
X
) and capacitor (C
X
). Once trig-
gered, the basic pulse width may be extended by retrigger-
ing the gated active-LOW transition or active-HIGH
transition inputs or be reduced by use of the active-LOW or
CLEAR input. Retriggering to 100% duty cycle is possible
by application of an input pulse train whose cycle time is
shorter than the output cycle time such that a continuous
“
HIGH
”
logic state is maintained at the
“
Q
”
output.
Operating Rules
1. An external resistor (R
X
) and an external capacitor (C
X
)
are required for proper operation. The value of C
X
may
vary from 0 to any necessary value. For small time con-
stants high-grade mica, glass, polypropylene, polycar-
bonate, or polystyrene material capacitors may be
used. For large time constants use tantalum or special
aluminum capacitors. If the timing capacitors have
leakages approaching 100 nA or if stray capacitance
from either terminal to ground is greater than 50 pF the
timing equations may not represent the pulse width the
device generates.
2. When an electrolytic capacitor is used for C
X
a switch-
ing diode is often required for standard TTL one-shots
to prevent high inverse leakage current. This switching
diode is not needed for the DM74LS123 one-shot and
should not be used. In general the use of the switching
diode is not recommended with retriggerable operation.
Furthermore, if a polarized timing capacitor is used on
the DM74LS123 the negative terminal of the capacitor
should be connected to the
“
C
EXT
”
pin of the device
(Figure 1).
FIGURE 1.
3. For C
X
>>
1000 pF the output pulse width (t
W
) is
defined as follows:
t
W
=
KR
X
C
X
where [R
X
is in k
]
[C
X
is in pF]
[t
W
is in ns]
K
≈
0.37
4. The multiplicative factor K is plotted as a function of C
X
below for design considerations:
FIGURE 2.
5. For C
X
<
1000 pF see Figure 3 for t
W
vs. C
X
family
curves with R
X
as a parameter:
FIGURE 3.
6. To obtain variable pulse widths by remote trimming, the
following circuit is recommended:
FIGURE 4.
“R
remote
” should be as close to the device pin as possible.
7. The retriggerable pulse width is calculated as shown
below:
T
=
t
W
+
t
PLH
=
K
×
R
X
×
C
X
+
t
PLH
The retriggered pulse width is equal to the pulse width
plus a delay time period (Figure 5).
FIGURE 5.
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| DM74LS125 WAF | 制造商:Fairchild Semiconductor Corporation 功能描述: |
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| DM74LS125AM | 功能描述:緩沖器和線路驅(qū)動(dòng)器 Quad 3-STATE Buffer RoHS:否 制造商:Micrel 輸入線路數(shù)量:1 輸出線路數(shù)量:2 極性:Non-Inverting 電源電壓-最大:+/- 5.5 V 電源電壓-最小:+/- 2.37 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Reel |
| DM74LS125AMX | 功能描述:緩沖器和線路驅(qū)動(dòng)器 Quad 3-STATE Buffer RoHS:否 制造商:Micrel 輸入線路數(shù)量:1 輸出線路數(shù)量:2 極性:Non-Inverting 電源電壓-最大:+/- 5.5 V 電源電壓-最小:+/- 2.37 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Reel |
| DM74LS125AN | 功能描述:緩沖器和線路驅(qū)動(dòng)器 Quad 3-STATE Buffer RoHS:否 制造商:Micrel 輸入線路數(shù)量:1 輸出線路數(shù)量:2 極性:Non-Inverting 電源電壓-最大:+/- 5.5 V 電源電壓-最小:+/- 2.37 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Reel |
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