ADR3412/ADR3420/ADR3425/ADR3430/ADR3433/ADR3440/ADR3450

Rev. B | Page 21 of 24

SAMPLE APPLICATIONS

Negative Reference

Figure 42 shows how to connect the ADR3450 and a standard

CMOS op amp, such as the AD8663, to provide a negative

reference voltage. This configuration provides two main

advantages: first, it only requires two devices and, therefore,

does not require excessive board space; second, and more

importantly, it does not require any external resistors, meaning

that the performance of this circuit does not rely on choosing

expensive parts with low temperature coefficients to ensure

accuracy.

AD8663

0.1µF

1µF

+VDD

–VDD

0.1µF

0.1µF

–5V

ADR3450

ENABLE

GND FORCE

GND SENSE

4

3

6

5

2

1

Figure 42. ADR3450 Negative Reference

ground, and the negative reference voltage and load current are

taken directly from the output of the operational amplifier. Note

that in applications where the negative supply voltage is close to

the reference output voltage, a dual-supply, low offset, rail-to-

rail output amplifier must be used to ensure an accurate output

voltage. The operational amplifier must also be able to source or

sink an appropriate amount of current for the application.

Bipolar Output Reference

Figure 43 shows a bipolar reference configuration. By connecting

the output of the ADR3450 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.

+15V

–15V

–5V

+5V

ADA4000-1

0.1µF

1µF

0.1µF

R1

10kΩ

R2

10kΩ

R3

5kΩ

ADR3450

ENABLE

GND FORCE

GND SENSE

4

3

6

5

2

1

Figure 43. ADR3450 Bipolar Output Reference

Boosted Output Current Reference

Figure 44 shows a configuration for obtaining higher current

drive capability from the ADR34xx references without

sacrificing accuracy. The op amp regulates the current flow

from the reference itself, allowing increased current drive

capability.

0.1µF

0.1µF

2N7002

AD8663

U6

+16V

0.1µF

1µF

R1

100Ω

200Ω

ADR34xx

ENABLE

GND FORCE

GND SENSE

4

3

6

5

2

1

Figure 44. Boosted Output Current Reference

Because the current-sourcing capability of this circuit depends

can be adjusted to the application simply by choosing an

be tied directly to the load device to maintain maximum output

voltage accuracy.