ADR4520ARZ-R7 datasheet(31/32 Pages) AD

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Data Sheet

ADR4520/ADR4525/ADR4530/ADR4533/ADR4540/ADR4550

Rev. 0 | Page 31 of 32

APPLICATIONS INFORMATION

BASIC VOLTAGE REFERENCE CONNECTION

The circuit shown in Figure 94 illustrates the basic configuration

for the ADR4520/ADR4525/ADR4530/ADR4533/ADR4540/

ADR4550 family of voltage references.

Figure 94. 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. 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 COUT Value

Part Number

Minimum COUT 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, the designer should keep

in mind that doing so will increase the turn-on time of the device.

LOCATION OF REFERENCE IN SYSTEM

The ADR4520/ADR4525/ADR4530/ADR4533/ADR4540/

ADR4550 reference should be placed 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 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.

SAMPLE APPLICATIONS

Bipolar Output Reference

Figure 95 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.

Figure 95. ADR4550 Bipolar Output Reference

Boosted Output Current Reference

Figure 96 shows a configuration for obtaining higher current

drive capability from the ADR4520/ADR4525/ADR4530/

ADR4533/ADR4540/ADR4550 references without sacrificing

accuracy. The op amp regulates the current flow through the

MOSFET until VOUT equals the output voltage of the reference;

current is then drawn directly from VIN instead of from the

reference itself, allowing increased current drive capability.

Figure 96. Boosted Output Current Reference

Because the current-sourcing capability of this circuit depends only

on the ID rating of the MOSFET, the output drive capability can

be adjusted to the application simply by choosing an appropriate

MOSFET. In all cases, the VOUT pin should be tied directly to the

load device to maintain maximum output voltage accuracy.

VIN

GND

VREF

BAND GAP

VIN

+15V

–15V

–5V

+5V

ADA4000-1

0.1µF

1µF

0.1µF

10kΩ

5kΩ

ADR4550

VIN

VOUT

GND

0.1µF

2N7002

AD8663

VIN

VOUT

+16V

0.1µF

1µF

100Ω

200Ω

ADR4520/ADR4525/

ADR4530/ADR4533/

ADR4540/ADR4550

VIN

VOUT

GND

PART

NUMBER

MINIMUM

ADR4520,

ADR4525

1.0µF

ADR4530,

ADR4533,

ADR4540,

ADR4550

0.1µF

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