REF193 AD [Analog Devices], REF193 Datasheet - Page 22

• Manufacturer Part Number: REF193
• Description: Precision Micropower, Low Dropout Voltage References
• Manufacturer: AD [Analog Devices]

REF19x Series
For V
low, thus U2 and Q1 are OFF, while U1 is ON. For V
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
default output comes from U1.
For the R1–R3 values as shown, the LOWER/UPPER V
thresholds are approximately 5.5 V and 6 V, respectively. These
can obviously be changed to suit other V
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
generally compatible with all family devices.
A Low Power, Strain Gage Circuit
As shown in Figure 12, the REF19x family of references can be
used in conjunction with low supply voltage operational amplifi-
ers, such as the OP492 and the OP283, in a self-contained strain
gage circuit. In this circuit, the REF195 was used as the core of
this low power, strain gage circuit. Other references 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.
S
levels lower than the LOWER threshold, U3’s output is
S
and is arranged so that when V
S
supplies, as can the
S
of 3.3 V, which is
S
fails, the
S
switching
S
levels
–22–
10 F
0.1 F
2.21k
Figure 12. A Low Power, Strain Gage Circuit
REF195
10k
1%
OP492
OP492
1/4
57k
1/4
1%
10k
10k
1%
1%
OP492
1 F
1/4
0.1 F
20k
20k
1%
1%
100
20k
1%
2N2222
500
0.1%
0.01 F
OP492
1/4
10 F
20k
1%
OUTPUT
REV. E