REF3112, 3120, 3125, 3130, 3133, 3140

8

SBVS046A

www.ti.com

NOISE PERFORMANCE

Typical 0.1Hz to 10Hz voltage noise can be seen in the

Typical Characteristic Curve,

0.1 to 10Hz Voltage Noise. The

noise voltage of the REF31xx increases with output voltage

and operating temperature. Additional filtering may be used

to improve output noise levels, although care should be

taken to ensure the output impedance does not degrade the

AC performance.

LONG-TERM STABILITY

Long-term stability refers to the change of the output voltage

of a reference over a period of months or years. This effect

lessens as time progresses, as is shown by the long-term

stability curves. The typical drift value for the REF31xx is

70ppm from 0-1000 hours. This parameter is characterized

by measuring 30 units at regular intervals for a period of 1000

hours.

LOAD REGULATION

Load regulation is defined as the change in output voltage

due to changes in load current. The load regulation of the

REF31xx is measured using force and sense contacts as

pictured in Figure 4. The force and sense lines reduce the

impact of contact and trace resistance, resulting in accurate

measurement of the load regulation contributed solely by the

REF31xx. For applications requiring improved load regula-

tion, force and sense lines should be used.

Output Pin

Meter

V

OUT

+

–

Sense Line

Force Line

Load

I

L

Contact and

Trace Resistance

FIGURE 4. Accurate Load Regulation of REF31xx.

APPLICATION CIRCUITS

Negative Reference Voltage

For applications requiring a negative and positive reference

voltage, the REF31xx and OPA703 can be used to provide

a dual supply reference from a

±5V supply. Figure 5 shows

the REF3125 used to provide a

±2.5V supply reference

voltage. The low drift performance of the REF31xx

complement the low offset voltage and low drift of the

OPA703 to provide an accurate solution for split-supply

applications.

OPA703

REF3125

+5V

–5V

+5V

10k

Ω

10k

Ω

+2.5V

–2.5V

FIGURE 5. REF3125 Combined with OPA703 to Create

Positive and Negative Reference Voltages.

DATA ACQUISITION

Data acquisition systems often require stable voltage

references to maintain accuracy. The REF31xx family features

stability and a wide range of voltages suitable for most micro-

controllers and data converters. Figure 6, Figure 7, and

Figure 8 show basic data acquisition systems.