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參數(shù)資料
| 型號： | REF19xGP |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Precision Micropower, Low Dropout, Voltage References |
| 中文描述： | 精密微功耗，低壓差，電壓基準(zhǔn) |
| 文件頁數(shù)： | 22/23頁 |
| 文件大?。?/td> | 238K |
| 代理商： | REF19XGP |
REF19x Series
–22–
REV. D
conditions, two REF195 devices are used for U1 and U2, with
their ON/OFF switching controlled by the presence or absence
of the primary dc supply source, V
S
. V
BAT
is a 6 V battery
backup source that supplies power to the load only when V
S
fails. For normal (V
S
present) power conditions, V
BAT
sees only
the 15
μ
A (max) standby current drain of U1 in its OFF state.
In operation, it is assumed that for all conditions either U1 or
U2 is ON and a 5 V reference output is available. With this
voltage constant, a scaled down version is applied to the com-
parator IC U3, providing a fixed 0.5 V input to the (–) input for
all power conditions. The R1–R2
divider provides a signal to
the U3 (+) input proportional to V
S
, which switches U3 and
U1/U2 dependent upon the absolute level of V
S
. Op amp U3 is
configured here as a comparator with hysteresis, which provides
for clean, noise free output switching. This hysteresis is impor-
tant to eliminate rapid switching at the threshold due to V
S
ripple. Further, the device chosen is the AD820, a rail-rail
output device, which provides HI and LO output states within a
few mV of V
S
and ground for accurate thresholds and compat-
ible drive for U2 for all V
S
conditions. R3 provides positive
feedback for circuit hysteresis, changing the threshold at the (+)
input as a function of U3’s output.
For V
S
levels lower than the LOWER threshold, U3’s output is
low, thus U2 and Q1 are OFF, while U1 is ON. For V
S
levels
higher than the UPPER threshold, the situation reverses, with
U1 OFF and both U2 and Q1 ON. In the interest of battery
power conservation, all of the comparison switching circuitry is
powered from V
S
and is so arranged that when V
S
fails the de-
fault output comes from U1.
For the R1–R3
values as shown, the LOWER/UPPER V
S
switching thresholds are approximately 5.5V and 6 V, respec-
tively. These can obviously be changed to suit other V
S
sup-
plies, as can the REF19x devices used for U1 and U2, over a
range of 2.5 V to 5 V of output. U3 can operate down to a V
S
of 3.3 V, which is generally compatible with all family devices.
A Low Power, Strain Gage Circuit
As shown in Figure 25, the REF19x family of references can
be used in conjunction with low supply voltage operational
amplifiers, such as the OP492 and the OP283, in a self-con-
tained strain gage circuit. In this circuit, the REF195 was used
as the core of this low power, strain gage circuit. Other refer-
ences can be easily accommodated by changing circuit element
values. The references play a dual role as the voltage regulator
to provide the supply voltage requirements of the strain gage
and the operational amplifiers as well as a precision voltage
reference for the current source used to stimulate the bridge. A
distinct feature of the circuit is that it can be remotely controlled
ON or OFF by digital means via the SLEEP pin.
500
V
0.1%
57k
V
1%
0.1
m
F
10k
V
1%
0.1
m
F
1/4
OP492
10
m
F
1
m
F
REF195
1/4
OP492
1/4
OP492
1/4
OP492
2.21k
V
20k
V
1%
10k
V
1%
20k
V
1%
20k
V
1%
0.01
m
F
10
m
F
100
V
OUTPUT
2N2222
20k
V
1%
10k
V
1%
Figure 25. A Low Power, Strain Gage Circuit
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| REF19xGRU | Precision Micropower, Low Dropout, Voltage References |
| REF19xGS | Precision Micropower, Low Dropout, Voltage References |
| REF194GRU | Precision Micropower, Low Dropout, Voltage References |
| REF195GRU | Precision Micropower, Low Dropout, Voltage References |
| REF191GP | Precision Micropower, Low Dropout, Voltage References |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| REF19XGRU | 制造商:AD 制造商全稱:Analog Devices 功能描述:Precision Micropower, Low Dropout, Voltage References |
| REF19XGRU4 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Precision Micropower, Low Dropout Voltage References |
| REF19XGS | 制造商:AD 制造商全稱:Analog Devices 功能描述:Precision Micropower, Low Dropout, Voltage References |
| REF19XSERIES | 制造商:AD 制造商全稱:Analog Devices 功能描述:Precision Micropower, Low Dropout, Voltage References |
| REF200 | 制造商:BB 制造商全稱:BB 功能描述:DUAL CURRENT SOURCE/CURRENT SINK |
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