- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄358839 > LM322N (NATIONAL SEMICONDUCTOR CORP) Precision Timers PDF資料下載
參數(shù)資料
| 型號： | LM322N |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 模擬波形發(fā)生器 |
| 英文描述： | Precision Timers |
| 中文描述： | RECTANGULAR, TIMER, PDIP14 |
| 封裝： | 0.300 INCH, PLASTIC, DIP-14 |
| 文件頁數(shù)： | 10/14頁 |
| 文件大?。?/td> | 281K |
| 代理商： | LM322N |
Typical Applications
(Continued)
In this application the logic terminal is normally held high by
R3. When a trigger pulse is received, Q1 is turned on, driv-
ing the logic terminal to ground. The result of triggering the
timer and reversing the logic at the same time is that the
output does not change from its initial low condition. The
only time the output will change states is when the trigger
input stays high longer than one time period set by R
t
and
C
t
. The output pulse width is equal to the input trigger width
minus R
t
#
C
t
. C2 insures no output pulse for short (
k
RC)
trigger pulses by prematurely resetting the timing capacitor
when the trigger pulse drops. C
L
filters the narrow spikes
which would occur at the output due to propagation delays
during switching.
5V Switching Regulator
Figure 13 is an application where the LM122 does not use
its timing function. A switching regulator is made using the
internal reference and comparator to drive a PNP transistor
switch. Features of this circuit include a 5.5V minimum input
voltage at 1A output current, low part count, and good effi-
ciency (
l
75%) for input voltages to 10V. Line and load
regulation are less than 0.5% and output ripple at the
switching frequency is only 30 mV. Q1 is an inexpensive
plastic device which does not need a heatsink for ambient
temperature up to 50
§
C. D1 should be a fast switching di-
ode. Output voltage can be adjusted between 1V and 30V
by choosing proper values for R2, R3, R4, and R5. For out-
puts less than 2V, a divider with 250
X
Thevinin resistance
must be connected between V
REF
and ground with its tap
point tied to V
ADJ
.
*
No. 22 Wire Wound on Molybdenum Permalloy Core
FIGURE 13. 5V Switching Regulator with
1 Amp Output and 5.5V Minimum Input
TL/H/7768–24
Application Hints
Aborting a Timing Cycle
The LM122 does not have an input specifically allocated to
a stop-timing function. If such a function is desired, it may be
accomplished several ways:
#
Ground V
ADJ
#
Raise R/C more positive than V
ADJ
#
Wire ‘‘OR’’ the output
Grounding V
ADJ
will end the timing cycle just as if the timing
capacitor had reached its normal discharge point. A new
timing cycle can be started by the trigger terminal as soon
as the ground is released. A switching transistor is best for
driving V
ADJ
to as near ground as possible. Worst case sink
current is about 300
m
A.
A timing cycle may also be ended by a positive pulse to a
resistor (R
s
R
t
/100) in series with the timing capacitor.
The pulse amplitude must be at least equal to V
ADJ
(2.0V),
but should not exceed 5.0V. When the timing capacitor dis-
charges, a negative spike of up to 2.0V will occur across the
resistor, so some caution must be used if the drive pulse is
used for other circuitry.
TL/H/7768–25
FIGURE 14. Cycle Interrupt
The output of the timer can be wire ORed with a discrete
transistor or an open collector logic gate output. This allows
overriding of the timer output, but does not cause the timer
to be reset until its normal cycle time has elapsed.
Using the LM122 as a Comparator
A built-in reference and zero volt common mode limit make
the LM122 very useful as a comparator. Threshold may be
adjusted from zero to three volts by driving the V
ADJ
termi-
nal with a divider tied to V
REF
. Stability of the reference
voltage is typically
g
1% over a temperature range of
b
55
§
C to
a
125
§
C. Offset voltage drift in the comparator is
typically 25
m
V/
§
C in the boosted mode and 50
m
V/
§
C un-
boosted. A resistor can be inserted in series with the input
to allow overdrives up to
g
50V as shown in Figure 15.
There is actually no limit on input voltage as long as current
is limited to
g
1 mA. The resistor shown contributes a worst
case of 5 mV to initial offset. In the unboosted mode, the
error drops to 0.25 mV maximum. The capability of operat-
ing off a single 5V supply with internal reference should
make this comparator very useful.
10
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM122H-MIL | Analog Timer Circuit |
| LM322 | Precision Timers |
| LM323A | 5.0 AMP POSITIVE VOLTAGE REGULATOR |
| LM323H | THREE-TERMINAL POSITIVE FIXED VOLTAGE REGULATORS |
| LM323KSTEEL | THREE-TERMINAL POSITIVE FIXED VOLTAGE REGULATORS |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM322N/B+ | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Analog Timer Circuit |
| LM323 | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Three-terminal 3 A adjustable voltage regulators |
| LM323/D | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Positive Voltage Regulators |
| LM323_02 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:3.0 A Positive Voltage Regulators |
| LM323_08 | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Three-terminal 3 A adjustable voltage regulators |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。