ADR4520ARZ-R7 datasheet(34/40 Pages) AD

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ADR4520/ADR4525/ADR4530/ADR4533/ADR4540/ADR4550

Data Sheet

Rev. D | Page 34 of 40

APPLICATIONS INFORMATION

BASIC VOLTAGE REFERENCE CONNECTION

The circuit shown in Figure 107 shows the basic configuration

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

ADR4550 family of voltage references.

VIN

GND

VREF

BAND GAP

Figure 107. 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 (COUT) is shown in Table 13.

Table 13. 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, 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 monitored carefully to ensure that the

device does not exceeded its maximum power dissipation rating.

The maximum power dissipation of the device can be calculated

using the following equation:

−

where:

PD is the device power dissipation.

TJ is the device junction temperature.

TA is the ambient temperature.

θJA is the package (junction to air) thermal resistance.

This relationship can cause acceptable load current in high

temperature conditions to 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 108 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 deployed in

environments with large temperature swings; otherwise, a voltage

difference develops between the two outputs as the ambient

temperature changes.

VIN

+15V

–15V

–5V

+5V

ADA4000-1

0.1µF

1µF

0.1µF

10kΩ

5kΩ

ADR4550

VIN

VOUT

GND

Figure 108. ADR4550 Bipolar Output Reference

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