REF3212,REF3220

REF3225,REF3230

REF3233,REF3240

SBVS058 −JUNE 2005

www.ti.com

10

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 Typical Characteristic curves. The

typical drift value for the REF32xx is 55ppm from 0 to 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

as a result of changes in load current. The load regulation

of the REF32xx is measured using force and sense

contacts, as shown in Figure 4. The force and sense lines

can be used to effectively eliminate the impact of contact

and trace resistance, resulting in accurate voltage at the

load. By connecting the force and sense lines at the load,

the REF32xx compensates for the contact and trace

resistances because it measures and adjusts the voltage

actually delivered at the load.

1

2

3

6

5

4

R

LOAD

0.47

µF

+5V

GND_F

Contact and Trace Resistance

GND_S

SHDN

OUT_F

OUT_S

IN

REF32xx

Figure 4. Accurate Load Regulation of REF32xx

APPLICATION CIRCUITS

NEGATIVE REFERENCE VOLTAGE

For applications requiring a negative and positive

reference voltage, the REF32xx and OPA735 can be used

to provide a dual-supply reference from a

±5V supply.

Figure 5 shows the REF3225 used to provide a

±2.5V

supply reference voltage. The low drift performance of the

REF32xx complements the low offset voltage and zero

drift of the OPA735 to provide an accurate solution for

split-supply applications. Care must be taken to match the

−2.5V

+2.5V

+5V

1

2

5

6

34

NOTE: Bypass capacitor is not shown.

R

1

10k

Ω R

2

10k

Ω

−5V

+5V

OPA735

REF3225

Figure 5. REF3225 Combined with OPA735 to

Create Positive and Negative Reference Voltages

DATA ACQUISITION

Data acquisition systems often require stable voltage

references to maintain accuracy. The REF32xx family

features stability and a wide range of voltages suitable for

most microcontrollers and data converters. Figure 6,

Figure 7, and Figure 8 show basic data acquisition

systems.