ADR3425/ADR3450

Rev. 0 | Page 16 of 20

SAMPLE APPLICATIONS

Negative Reference

Figure 42 shows how to connect the ADR3425/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 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 ADR3425/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.

VIN

+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. Bipolar Output Reference

Boosted Output Current Reference

Figure 44 shows a configuration for obtaining higher current

drive capability from the ADR3425/ADR3450 references

without sacrificing accuracy. The op amp regulates the current

of from the reference itself, allowing increased current drive

capability.

0.1µF

0.1µF

2N7002

AD8663

VIN

U6

VOUT

+16V

0.1µF

1µF

R1

100Ω

200Ω

ADR3450

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.