Datasheet

REF01/REF02/REF03 Data Sheet
Rev. M | Page 16 of 20
APPLICATIONS INFORMATION
BASIC REFERENCE APPLICATION
Figure 38 shows the basic configuration for any
REF01/REF02/REF03 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
V
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
REF01/REF02/REF03 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
V
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
TEM
P
TRIM
GND
V
–
V+
OP
1
177
–5V TO V
L
AD5201
0V TO (5V + V
L
)
+12V
R
SET
1kΩ
R
L
I
L
V
L
1kΩ
100k
Ω
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
DV
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
REF01/REF02/REF03 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
V
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.