ADR440/ADR441/ADR443/ADR444/ADR445

Rev. A | Page 15 of 20

APPLICATIONS

OUTPUT ADJUSTMENT

The ADR44x family features a TRIM pin that allows the user to

adjust the output voltage of the part over a limited range. This

allows errors from the reference and overall system errors to be

trimmed out by connecting a potentiometer between the output

and the ground, with the wiper connected to the TRIM pin.

Figure 35 shows the optimal trim configuration. R1 allows fine

be sufficiently large so that the maximum output current from

the ADR44x is not exceeded.

TRIM

0.1µF

0.1µF

GND

R2

1kΩ

10kΩ

2

5

4

R1

100kΩ

ADR440/

ADR441/

ADR443/

ADR444/

ADR445

Figure 35. ADR44x Trim Function

Using the trim function has a negligible effect on the temperature

performance of the ADR44x. However, all resistors need to be

low temperature coefficient resistors, or errors can occur.

BIPOLAR OUTPUTS

By connecting the output of the ADR44x to the inverting

terminal of an operational amplifier, it is possible to obtain both

positive and negative reference voltages. Care must be taken

when choosing Resistor R1 and Resistor R2 (see Figure 36).

They must be matched as closely as possible to ensure minimal

differences between the negative and positive outputs. In

addition, care must be taken to ensure performance over

temperature. Use low temperature coefficient resistors if the

circuit is used over temperature; otherwise, differences exist

between the two outputs.

ADR440/

ADR441/

ADR443/

ADR444/

ADR445

6

2

4

GND

R1

10kΩ

R2

10kΩ

R3

5kΩ

–10V

+10V

–5V

+5V

0.1µF

0.1µF

Figure 36. ADR44x Bipolar Outputs

NEGATIVE REFERENCE

Figure 37 shows how to connect the ADR44x and a standard

operational amplifier, such as the OP1177, to provide negative

voltage. This configuration provides two main advantages. First,

it only requires two devices; therefore, it does not require

excessive board space. Second, and more importantly, it does

not require any external resistors. This means the performance

of this circuit does not rely on choosing low temperature

coefficient resistors to ensure accuracy.

ADR440/

ADR441/

ADR443/

ADR444/

ADR445

GND

2

6

4

Figure 37. ADR44x Negative Reference

directly from the output of the operational amplifier. If the

negative supply voltage is close to the reference output, the

operational amplifier must be dual supply and have low offset

and rail-to-rail capability.