參數(shù)資料
型號: ADR370BRT-R2
廠商: ANALOG DEVICES INC
元件分類: 基準(zhǔn)電壓源/電流源
英文描述: Precision Low Power 2.048 V SOT-23 Voltage Reference
中文描述: 1-OUTPUT THREE TERM VOLTAGE REFERENCE, 2.048 V, PDSO3
封裝: TO-236AB, SOT-23-3
文件頁數(shù): 7/12頁
文件大?。?/td> 182K
代理商: ADR370BRT-R2
REV. A
ADR370
–7–
APPLICATIONS
Low Cost Negative Reference
A low cost negative reference can be obtained by leveraging the
current sinking capability of the ADR370. Simply tying the V
OUT
terminal to ground and adding a bias resistor, R
SET
, to the GND
pin of the device, a negative voltage reference can be obtained
as shown in Figure 3. R
SET
should be chosen such that I
SET
remains between 1 mA to 5 mA.
V
IN
V
DD
V
SS
R
SET
I
SET
ADR370
V
OUT
GND
–VREF
Figure 3. Low Cost Negative Reference
Precision Negative Reference
Without using any matching resistors, a precision negative reference
can be obtained using the configuration shown in Figure 4. The
voltage difference between V
OUT
and GND of the ADR370 is
2.048 V. Since V
OUT
is at virtual ground, U2 will close the loop by
forcing the GND pin to be the negative reference node. U2 should
be a low offset voltage precision op amp, such as the OP1177.
V
IN
+15V
U2
U1
2.3V TO 12V
OP1177
–15V
ADR370
V
OUT
GND
–VREF
Figure 4. Precision Negative Reference
Low Cost Current Source
Figure 5 illustrates how a simple, low cost current source can be
configured using the ADR370. The load current, I
L
, is simply
the sum of I
SET
and the quiescent current, I
q
. I
SET
is simply the
reference voltage generated by the ADR370 divided by R
SET
.
V
R
SET
The quiescent current, I
q
, varies slightly with load. The variation
in I
q
limits the use of this circuit to general-purpose applications.
I
SET
=
2 048
.
(4)
V
IN
V
L
+ 2.5V < V
DD
< V
L
+ 12V
ADR370
V
OUT
GND
I
SET
=
R
SET
R
SET
V
L
R
L
I
L
I
q
= 65 A
2.048V
Figure 5. Low Cost Current Source
Precision Current Source with Adjustable Output
A precision current source can be implemented with the circuit
shown in Figure 6. By adding a mechanical or digital potenti-
ometer, this circuit becomes an adjustable current source. If a
digital potentiometer like the AD5201 is used, the load current
is simply the voltage across terminals B-to-W of the digital
potentiometer divided by R
SET
.
V
D
R
SET
×
256
where
D
is the decimal equivalent of the digital potentiometer
input code.
I
L
REF
=
×
(5)
V
IN
+12V
A
B
W
–2.048V TO V
L
0V TO (2.048V + V
L
)
12V
OP1177
AD5201
–12V
ADR370
V
OUT
GND
V
L
R
L
R
SET
I
L
Figure 6. Programmable 0 mA to 5 mA Current Source
To optimize the resolution of this circuit, dual supply op amps
should be used because the ground potential of ADR370 can
swing from
2.048 V at zero scale to V
L
at full scale of the
potentiometer setting.
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