REF01/REF02/REF03
Rev. K | Page 16 of 20
APPLICATIONS INFORMATION
BASIC REFERENCE APPLICATION
Figure 38 shows the basic configuration for any REF0x device.
Input and output capacitance values can be tailored for
performance, provided they follow the guidelines described
in the Input and Output Capacitors section.
U1
REF01/
REF02/
REF03
V
O
C2
0.1µF
C1
0.1µF
IN
V
IN
V
OUT
TEMP
TRIM
GND
00375-038
Figure 38. Basic Reference Application
LOW COST CURRENT SOURCE
Unlike most references, the quiescent current of the REF0x
series remains constant with respect to the load current (refer to
Figure 22)
. As a result, a simple, low cost current source can be
constructed by configuring the reference as shown in Figure 39.
REF01/
REF02/
REF03
V
OUT
GND
IN
I
IN
I
SET
= (V
OUT
– V
L
)/R
SET
R
SET
I
Q
≈ 0.6mA
I
L
= I
SET
+ I
Q
V
L
R
L
00375-040
Figure 39. Simple Current Source
In this configuration, the current through the resistor R
SET
(I
SET
)
is equal to (V
OUT
− V
L
)/R
SET
. I
L
is simply the sum of I
SET
and I
Q
.
However, since I
Q
typically varies from 0.55 mA to 0.65 mA,
this circuit should be limited to low precision, general-purpose
applications.
PRECISION CURRENT SOURCE WITH ADJUSTABLE
OUTPUT
A higher-precision current source can be implemented with the
circuit shown in Figure 40.
U2
+12V
–12V
W
B
A
U1
REF02
V
IN
V
OUT
TEMP
TRIM
GND
V–
V+
OP1177
–5V TO V
L
AD5201
0V TO (5V + V
L
)
+12
R
SET
1kΩ
R
L
I
L
V
L
1kΩ
100kΩ
00375-041
Figure 40. Programmable 0 mA to 5 mA Current Source
By adding a mechanical or digital potentiometer, this circuit
becomes an adjustable current source. If a digital potentiometer
is used, the load current is simply the voltage across terminal B
to terminal W of the digital potentiometer divided by the value
of the resistor R
SET
.
[]
A
SET
REF
L
R
D
I
×
=
where
D is the decimal equivalent of the digital potentiometer
input code.
A dual-supply op amp should be used since the ground
potential of REF02 can swing from −5.0 V to V
L
while the
potentiometer is swung from zero-scale to full-scale.
PRECISION BOOSTED OUTPUT REGULATOR
The output current sourcing capability of the REF0x series can
be boosted by using an external op amp and MOSFET, as shown
in Figure 41.
U2
15V
N1
200Ω
U1
REF01/
REF02/
REF03
V
IN
V
OUT
TEMP
TRIM
GND
V–
V+
OP1177
2N7002
IN
V
O
R
L
1µF
C
L
00375-042
C
1
1000pF
R
2
100Ω
R
1
100Ω
Figure 41. Precision Boosted Output Regulator
In this circuit, U2 forces V
O
to V
REF
by regulating the current
through N1, thereby sourcing the load current directly from the
input voltage source connected at V
IN
. Using the components
shown, this circuit can source up to 50 mA with an input volt-
age of 15.0 V. The circuit’s current sourcing capability can be
further increased by replacing N1 with a higher-power MOSFET.
