ADR370 Analog Devices, Inc., ADR370 Datasheet - Page 9

• Manufacturer Part Number: ADR370
• Description: Precision Low Power 2.048 V Sot-23 Voltage Reference
• Manufacturer: Analog Devices, Inc.

APPLICATIONS INFORMATION
LOW COST NEGATIVE REFERENCE
A low cost negative reference can be obtained by leveraging the
current sinking capability of the ADR370. By simply tying the
V
GND pin of the device, a negative voltage reference can be
obtained as shown in Figure 14. R
I
PRECISION NEGATIVE REFERENCE
Without using any matching resistors, a precision negative
reference can be obtained using the configuration shown in
Figure 15. The voltage difference between V
ADR370 is 2.048 V. Because V
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
LOW COST CURRENT SOURCE
Figure 16 illustrates how a simple, low cost current source can
be configured using the ADR370. The load current, I
the sum of I
reference voltage generated by the ADR370 divided by R
The quiescent current, I
in I
SET
OUT
q
remains between 1 mA to 5 mA.
limits the use of this circuit to general-purpose applications.
I
terminal to ground and adding a bias resistor (R
OP1177.
SET
=
2.3V TO 12V
SET
. 2
R
048
–VREF
V
and the quiescent current, I
SET
DD
Figure 14. Low Cost Negative Reference
Figure 15. Precision Negative Reference
V
U1
V
V
q
IN
IN
R
, varies slightly with load. The variation
ADR370
ADR370
SET
GND
GND
V
SS
OUT
OP1177
V
V
I
OUT
SET
OUT
SET
is at virtual ground, U2 closes
should be chosen such that
U2
+15V
–15V
q
. I
OUT
–VREF
SET
and GND of the
is simply the
L
SET
, is simply
) to the
SET
.
Rev. B | Page 9 of 12
(4)
PRECISION CURRENT SOURCE WITH ADJUSTABLE
OUTPUT
A precision current source can be implemented with the circuit
shown in Figure 17. By adding a mechanical or digital potenti-
ometer, this circuit becomes an adjustable current source. If a
digital potentiometer, such as the
current is simply the voltage across terminals B-to-W of the
digital potentiometer divided by R
where D is the decimal equivalent of the digital potentiometer
input code.
To optimize the resolution of this circuit, dual-supply op amps
should be used because the ground potential of the ADR370
can swing from −2.048 V at zero scale to V
potentiometer setting.
V
L
+ 2.5V < V
I
L
12V
=
Figure 17. Programmable 0 mA to 5 mA Current Source
R
DD
V
SET
REF
< V
×
–2.048V TO V
V
L
×
IN
+ 12V
256
Figure 16. Low Cost Current Source
ADR370
D
GND
V
V
IN
L
OUT
ADR370
I
OP1177
q
GND
= 65µA
AD5201
V
0V TO (2.048V + V
OUT
AD5201
SET
.
+12V
–12V
B
A
is used, the load
L
W
at full scale of the
R
SET
R
L
)
R
L
L
V
R
ADR370
L
SET
I
I
L
SET
I
L
V
L
=
2.048V
R
SET
(5)