ADR03 AD [Analog Devices], ADR03 Datasheet - Page 31

• Manufacturer Part Number: ADR03
• Description: Ultralow Noise, High Accuracy
• Manufacturer: AD [Analog Devices]

Data Sheet
APPLICATIONS INFORMATION
BASIC VOLTAGE REFERENCE CONNECTION
The circuit shown in Figure 94 illustrates the basic configuration
for the
ADR4550
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. An additional 0.1 μF ceramic
capacitor should be connected 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
Part Number
ADR4520, ADR4525
ADR4530, ADR4533,
ADR4540, ADR4550
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, the designer should keep
in mind that doing so will increase the turn-on time of the device.
LOCATION OF REFERENCE IN SYSTEM
The
ADR4550
to minimize the length of the output traces and, therefore, the error
introduced by the voltage drop. Current flowing through a PCB
trace produces an IR 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
can introduce a full millivolt of error.
Figure 94.
ADR4520/ADR4525/ADR4530/ADR4533/ADR4540/
ADR4520/ADR4525/ADR4530/ADR4533/ADR4540/
reference should be placed as close to the load as possible
family of voltage references.
ADR4520/ADR4525/ADR4530/ADR4533/ADR4540/ADR4550
BAND GAP
OUT
Simplified Schematic
Value
GND
Minimum C
1.0 µF
0.1 µF
V
IN
OUT
ADR4520/ADR4525/ADR4530/ADR4533/ADR4540/ADR4550
V
Value
REF
Rev. 0 | Page 31 of 32
SAMPLE APPLICATIONS
Bipolar Output Reference
Figure 95 shows a bipolar reference configuration. By connecting
the output of the
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.
Boosted Output Current Reference
Figure 96 shows a configuration for obtaining higher current
drive capability from the
ADR4533/ADR4540/ADR4550
accuracy. The op amp regulates the current flow through the
MOSFET until V
current is then drawn directly from V
reference itself, allowing increased current drive capability.
Because the current-sourcing capability of this circuit depends only
on the I
be adjusted to the application simply by choosing an appropriate
MOSFET. In all cases, the V
load device to maintain maximum output voltage accuracy.
V
IN
1µF
1µF
0.1µF
D
2
rating of the MOSFET, the output drive capability can
ADR4520/ADR4525/
ADR4530/ADR4533/
0.1µF
ADR4540/ADR4550
V
IN
Figure 95.
Figure 96. Boosted Output Current Reference
2
ADR4550
OUT
V
IN
U6
equals the output voltage of the reference;
ADR4550
ADR4550
V
ADR4520/ADR4525/ADR4530/
GND
OUT
OUT
to the inverting terminal of an
V
6
4
pin should be tied directly to the
Bipolar Output Reference
IN
V
GND
references without sacrificing
OUT
C
L
6
4
PART
NUMBER
ADR4520,
ADR4525
ADR4530,
ADR4533,
ADR4540,
ADR4550
IN
0.1µF
+16V
ADA4000-1
instead of from the
AD8663
100Ω
R1
5kΩ
R3
MINIMUM
C
1.0µF
0.1µF
L
R1
10kΩ
2N7002
10kΩ
R2
–15V
+15V
200Ω
R
L
+5V
–5V
V
C
0.1µF
OUT
L