- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄358839 > LM122H-MIL Analog Timer Circuit PDF資料下載
參數(shù)資料
| 型號： | LM122H-MIL |
| 英文描述： | Analog Timer Circuit |
| 中文描述： | 模擬定時器電路 |
| 文件頁數(shù)： | 9/14頁 |
| 文件大小： | 281K |
| 代理商： | LM122H-MIL |
Typical Applications
(Continued)
The average charging current through R
t
is about 30 nA, so
some attention must be paid to parts layout to prevent stray
leakage paths. The suggested timing capacitor has a typical
self time constant of 300 hours and a guaranteed minimum
of 25 hours at
a
25
§
C. Other capacitor types may be used if
sufficient data is available on their leakage characteristics.
Two Terminal Time Delay Switch
The LM122 can be used as a two terminal time delay switch
if an ‘‘on’’ voltage drop of 2V to 3V can be tolerated. In
Figure 9, the timer is used to drive a relay ‘‘on’’ R
t
#
C
t
seconds after application of power. ‘‘Off’’ current of the
switch is 4 mA maximum, and ‘‘on’’ current can be as high
as 50 mA.
Zero Power Dissipation Between Timing Intervals
In some applications it is desirable to reduce supply current
drain to zero between timing cycles. In Figure 10 this is
accomplished by using an external PNP as a latch to drive
the V
a
pin of the timer.
Between timing periods Q1 is off and no supply current is
drawn. When a trigger pulse of 5V minimum amplitude is
received, the LM122 output transistor and Q1 latch for the
duration of the timing period. D1 prevents the step on the
V
a
pin from coupling back into the trigger pin. If the trigger
input is a short pulse, C1 and R2 may be eliminated. R
L
must have a minimum value of (V
CC
)/(2.5 mA).
TL/H/7768–20
FIGURE 9. 2-Terminal Time Delay Switch
Frequency to Voltage Converter
An accurate frequency to voltage converter can be made
with the LM122 by averaging output pulses with a simple
one pole filter as shown inFigure 11. Pulse width is adjusted
with R2 to provide initial calibration at 10 kHz. The collector
of the output transistor is tied to V
REF
, giving constant am-
plitude pulses equal to V
REF
at the emitter output. R4 and
C1 filter the pulses to give a dc output equal to,
(R
t
)(C
t
)(V
REF
)(f). Linearity is about 0.2% for a 0V to 1V out-
put. If better linearity is desired R5 can be tied to the sum-
ming node of an op amp which has the filter in the feedback
path. If a low output impedance is desired, a unity gain buff-
er such as the LM110 can be tied to the output. An analog
meter can be driven directly by placing it in series with R5 to
ground. A series RC network across the meter to provide
damping will improve response at very low frequencies.
Pulse Width Detector
By driving the logic terminal of the LM122 simultaneous to
the trigger input, a simple, accurate pulse width detector can
be made (Figure 12).
TL/H/7768–21
FIGURE 10. Zero Power Dissipation
Between Timing Intervals
TL/H/7768–22
FIGURE 11. Frequency to Voltage Converter.
(Tachometer) Output Independent of Supply Voltage.
TL/H/7768–23
*
V
OUT
e
0 for W R
1
C
1
Pulse Out
e
W
b
R
1
C
1
for W R
1
C
1
FIGURE 12. Pulse Width Detector
9
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM322 | Precision Timers |
| LM323A | 5.0 AMP POSITIVE VOLTAGE REGULATOR |
| LM323H | THREE-TERMINAL POSITIVE FIXED VOLTAGE REGULATORS |
| LM323KSTEEL | THREE-TERMINAL POSITIVE FIXED VOLTAGE REGULATORS |
| LM123KSTEEL-MIL | THREE-TERMINAL POSITIVE FIXED VOLTAGE REGULATORS |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM122M/IA-MIL | 制造商:QP Semiconductor 功能描述:LM122 883 LEVEL CAN-NSC |
| LM123 | 制造商:SEME-LAB 制造商全稱:Seme LAB 功能描述:3 AMP POSITIVE VOLTAGE REGULATORS |
| LM123-05 | 制造商:SEME-LAB 制造商全稱:Seme LAB 功能描述:3 AMP POSITIVE VOLTAGE REGULATORS |
| LM123-12 | 制造商:SEME-LAB 制造商全稱:Seme LAB 功能描述:3 AMP POSITIVE VOLTAGE REGULATORS |
| LM123-15 | 制造商:SEME-LAB 制造商全稱:Seme LAB 功能描述:3 AMP POSITIVE VOLTAGE REGULATORS |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。