ref195gru-reel Analog Devices, Inc., ref195gru-reel Datasheet - Page 24

• Manufacturer Part Number: ref195gru-reel
• Description: Precision Micropower, Low Dropout Voltage References
• Manufacturer: Analog Devices, Inc.

REF19x Series
For V
thus, U2 and Q1 are off while U1 is on. For V
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
default output comes from U1.
For the R1 to R3 values, as shown in Figure 30, lower/upper V
switching thresholds are approximately 5.5 V and 6 V, respectively.
These can be changed to suit other V
devices used for U1 and U2, over a range of 2.5 V to5 V of output.
U3 can operate down to a V
compatible with all REF19x family devices.
LOW POWER, STRAIN GAGE CIRCUIT
As shown in Figure 31, the REF19x family of references can be
used in conjunction with low supply voltage operational amplifiers,
such as the OP492 or the OP283, in a self-contained strain gage
circuit in which the REF195 is used as the core. Other
references can be easily accommodated by changing circuit
element values. The references play a dual role, first as the
voltage regulator to provide the supply voltage requirements of
the strain gage and the operational amplifiers, and second 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.
S
levels lower than the lower threshold, U3 output is low;
S
and is arranged so that when V
S
of 3.3 V, which is generally
S
supplies, as can the REF19x
S
levels higher
S
fails, the
S
Rev. I | Page 24 of 28
10µF
2.21kΩ
+
0.1µF
2
REF195
4
13
12
10
9
Figure 31. A Low Power, Strain Gage Circuit
10kΩ
1%
OP492
OP492
–
+
–
+
1/4
1/4
10kΩ
10kΩ
6
57kΩ
1%
1%
1%
3
2
+
1µF
+
OP492
–
14
1/4
8
11
4
0.1µF
100Ω
20kΩ
20kΩ
1%
1%
1
20kΩ
1%
2N2222
0.01µF
6
5
500Ω
0.1%
OP492
+
–
1/4
10µF
20kΩ
1%
7
OUTPUT