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參數(shù)資料
| 型號： | LMV7291MGX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 比較器 |
| 英文描述： | Single 1.8V Low Power Comparator with Rail-to-Rail Input |
| 中文描述： | COMPARATOR, 6000 uV OFFSET-MAX, PDSO5 |
| 封裝： | SC-70, 5 PIN |
| 文件頁數(shù)： | 10/14頁 |
| 文件大小： | 400K |
| 代理商： | LMV7291MGX |
Application Notes
BASIC COMPARATOR
A comparator is often used to convert an analog signal to a
digital signal. As shown in
Figure 2
, the comparator com-
pares an input voltage (V
IN
) to a reference voltage (V
REF
). If
V
is less than V
REF
, the output (V
) is low. However, if V
IN
is greater than V
REF
, the output voltage (V
O
) is high.
RAIL-TO-RAIL INPUT STAGE
The LMV7291 has an input common mode voltage range
(V
) of 0.1V below the V
to 0.1V above V
+
. This is
achieved by using paralleled PNP and NPN differential input
pairs. When the V
CM
is near V
+
, the NPN pair is on and the
PNP pair is off. When the V
CM
is near V
, the NPN pair is off
and the PNP pair is on. The crossover point between the
NPN and PNP input stages is around 950mV from V
+
. Since
each input stage has its own offset voltage (V
OS
), the V
OS
of
the comparator becomes a function of the V
CM
. See curves
for V
OS
vs. V
CM
in Typical Performance Characteristics sec-
tion. In application design, it is recommended to keep the
V
CM
away from the crossover point to avoid problems. The
wide input voltage range makes LMV7291 ideal in power
supply monitoring circuits, where the comparators are used
to sense signals close to gnd and power supplies.
OUTPUT STAGE
The LMV7291 has a push-pull output stage. This output
stage keeps the total system power consumption to the
absolute minimum. The only current consumed is the low
supply current and the current going directly into the load.
When output switches, both PMOS and NMOS at the output
stage are on at the same time for a very short time. This
allows current to flow directly between V
+
and V
through
output transistors. The result is a short spike of current
(shoot-through current) drawn from the supply and glitches
in the supply voltages. The glitches can spread to other parts
of the board as noise. To prevent the glitches in supply lines,
power supply bypass capacitors must be installed. See sec-
tion for supply bypassing in the Application Notes for details.
HYSTERESIS
It is a standard procedure to use hysteresis (positive feed-
back) around a comparator, to prevent oscillation, and to
avoid excessive noise on the output because the comparator
is a good amplifier of its own noise.
Inverting Comparator with Hysteresis
The inverting comparator with hysteresis requires a three
resistor network that are referenced to the supply voltage
V
CC
of the comparator (
Figure 3
). When V
IN
at the inverting
input is less than V
A
, the voltage at the non-inverting node of
the comparator (V
IN
<
V
A
), the output voltage is high (for
simplicity assume V
O
switches as high as V
CC
). The three
network resistors can be represented as R
||R
in series with
R
2
. The lower input trip voltage V
A1
is defined as
When V
is greater than V
(V
>
V
), the output voltage is
low and very close to ground. In this case the three network
resistors can be presented as R
//R
3
in series with R
1
. The
upper trip voltage V
A2
is defined as
The total hysteresis provided by the network is defined as
V
A
= V
A1
- V
A2
A good typical value of
V
would be in the range of 5 to 50
mV. This is easily obtained by choosing R
as 1000 to 100
times (R
||R
) for 5V operation, or as 300 to 30 times
(R
1
||R
2
) for 1.8V operation.
LMV7291
20080025
20080017
FIGURE 2. LMV7291 Basic Comparator
L
www.national.com
10
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LMV7291MGX/NOPB | 功能描述:校驗(yàn)器 IC RoHS:否 制造商:STMicroelectronics 產(chǎn)品: 比較器類型: 通道數(shù)量: 輸出類型:Push-Pull 電源電壓-最大:5.5 V 電源電壓-最小:1.1 V 補(bǔ)償電壓（最大值）:6 mV 電源電流（最大值）:1350 nA 響應(yīng)時(shí)間: 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SC-70-5 封裝:Reel |
| LMV751 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Low Noise, Low Vos, Single Op Amp |
| LMV751M5 | 功能描述:運(yùn)算放大器 - 運(yùn)放 RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LMV751M5/NOPB | 功能描述:運(yùn)算放大器 - 運(yùn)放 Ultra Low Noise Sgl Op Amp RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LMV751M5/NOPB | 制造商:Texas Instruments 功能描述:Operational Amplifier (Op-Amp) IC |
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