Datasheet

Data Sheet ADR4520/ADR4525/ADR4530/ADR4533/ADR4540/ADR4550
Rev. B | Page 31 of 37
APPLICATIONS INFORMATION
BASIC VOLTAGE REFERENCE CONNECTION
The circuit shown in Figure 82 shows the basic configuration
for the ADR4520/ADR4525/ADR4530/ADR4533/ADR4540/
ADR4550 family of voltage references.
10203-054
V
IN
GND
V
REF
BAND GAP
Figure 83. ADR4520/ADR4525/ADR4530/ADR4533/ADR4540/ADR4550
Simplified Schematic
INPUT AND OUTPUT CAPACITORS
Input Capacitors
A 1 μF to 10 μF electrolytic or ceramic capacitor can be connected
to the input to improve transient response in applications where
the supply voltage may fluctuate. It is recommended to connect
an additional 0.1 μF ceramic capacitor in parallel to reduce supply
noise.
Output Capacitors
An output capacitor is required for stability and to filter out low
level voltage noise. The minimum value of the output capacitor
is shown in Table 12.
Table 12. Minimum C
OUT
Value
Part Number Minimum C
OUT
Value
ADR4520, ADR4525
1.0 µF
ADR4530, ADR4533,
ADR4540, ADR4550
0.1 µF
An additional 1 μF to 10 μF electrolytic or ceramic capacitor can be
added in parallel to improve transient performance in response to
sudden changes in load current; however, doing so increases the
turn-on time of the device.
LOCATION OF REFERENCE IN SYSTEM
It is recommended to place the ADR4520/ADR4525/ADR4530/
ADR4533/ADR4540/ADR4550 reference as close to the load as
possible to minimize the length of the output traces and, therefore,
the error introduced by the voltage drop. Current flowing through
a PCB trace produces a voltage drop; with longer traces, this
drop can reach several millivolts or more, introducing considerable
error into the output voltage of the reference. A 1 inch long, 5 mm
wide trace of 1 ounce copper has a resistance of approximately
100 mΩ at room temperature; at a load current of 10 mA, this
resistance can introduce a full millivolt of error.
POWER DISSIPATION
The ADR4520/ADR4525/ADR4530/ADR4533/ADR4540/
ADR4550 voltage references are capable of sourcing and sinking
up to 10 mA of load current at room temperature across the rated
input voltage range. However, when used in applications subject
to high ambient temperatures, the input voltage and load current
must be carefully monitored to ensure that the device does not
exceeded its maximum power dissipation rating. The maximum
power dissipation of the device can be calculated via the following
equation:
JA
A
J
D
TT
P
θ
−
=
where:
P
D
is the device power dissipation.
T
J
is the device junction temperature.
T
A
is the ambient temperature.
θ
JA
is the package (junction to air) thermal resistance.
Due to this relationship, acceptable load current in high
temperature conditions can be less than the maximum current
sourcing capability of the device. Do not operate the device
outside of its maximum power rating, because doing so can
result in premature failure or permanent damage to the device.
SAMPLE APPLICATIONS
Bipolar Output Reference
Figure 83 shows a bipolar reference configuration. By connecting
the output of the ADR4550 to the inverting terminal of an
operational amplifier, it is possible to obtain both positive and
negative reference voltages. R1 and R2 must be matched as closely
as possible to ensure minimal difference between the negative
and positive outputs. Resistors with low temperature coefficients
must also be used if the circuit is used in environments with large
temperature swings; otherwise, a voltage difference develops
between the two outputs as the ambient temperature changes.
V
IN
+15V
–15V
–5V
+5V
ADA4000-1
0.1µF1µF
0.1µF
R1
10kΩ
R2
10kΩ
R3
5kΩ
ADR4550
V
IN
V
OUT
GND
2 6
4
10203-055
Figure 84. ADR4550 Bipolar Output Reference
Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.