ADR280
Rev. C | Page 8 of 12
APPLICATIONS INFORMATION
The ADR280 should be decoupled with a 0.1 μF ceramic
capacitor at the output for optimum stability. It is also good
practice to include 0.1 μF ceramic capacitors at the IC supply
pin. These capacitors should be mounted close to their
respective pins (see
Figure 12).
V+
V–
ADR280
V
OUT
0.1µF
0.1µF
03065-014
Figure 12. Basic Configuration
The low supply voltage input pin V− can be elevated above
ground; a 1.2 V differential voltage can therefore be established
above V− (see
Figure 13).
V+
V–
ADR280
5V
1.2V + V–
2.5V
V
OUT
0.1µF
0.1µF
03065-015
Figure 13. Floating References
The ADR280 provides the core 1.2 V band gap voltage and is
able to drive a maximum load of only 100 μA. Users can simply
buffer the output for high current or sink/source current applica-
tions, such as ADC or LCD driver references (see
Figure 14).
V+
ADR280
U1
U2
V
OUT
V–
0.1µF
OUT
0.1µF
U2 = AD8541, SC70
AD8601, SOT-23-5
03065-016
Figure 14. Buffered Output
Users can also tailor any specific need for voltage and dynamics
with an external op amp and discrete components (see
Figure 14
and
Figure 15). Depending on the specific op amp and PCB
layout, it may be necessary to add a compensation capacitor, C2,
to prevent gain peaking and oscillation. The exact value of C2
needed requires some trial and error but usually falls in the
range of a few picofarads.
V+
V–
ADR280
U1
5V
5V
1.2V
U2
1.8V
C2
2.2pF
V+
V–
AD8541
C1
0.1µF
V
OUT
+
–
V
O
R2
60kΩ ± 0.1%
R1
120kΩ ± 0.1%
03065-017
Figure 15. 1.8 V Reference
LOW COST, LOW POWER CURRENT SOURCE
Because of its low power characteristics, the ADR280 can be
converted to a current source with just a setting resistor. In
addition to the ADR280 current capability, the supply voltage
and the load limit the maximum current. The circuit in
Figure 16
produces 100 μA with 2 V compliance at a 5 V supply. The load
current is the sum of I
SET
and I
GND
. I
GND
increases slightly with
load; a R
SET
of 13.6 kΩ yields 100 μA of load current.
V+
V–
ADR280
U1
5V
C1
0.1µF
RL
1kΩ
+
–
I
SET
V
OUT
13.6kΩ
R
SET
1.2V
I
GND
I
L
=I
SET
+I
GND
I
L
100µA
03065-018
Figure 16. Low Cost Current Source
Precision Low Power Current Source
By adding a buffer to redirect the I
GND
in Figure 17, a current
can be precisely set by R
SET
with the equation I
L
= 1.2 V/R
SET
.
V+
V–
ADR280
U1
5V
V+
V–
5V
U2
AD8541
–
+
V
OUT
C2
0.1µF
R
SET
12kΩ
RL
1kΩ
I
L
100µA
I
L
=1.2V/R
SET
03065-019
Figure 17. Precision Low Power Current Source
