REF3212,REF3220

REF3225,REF3230

REF3233,REF3240

SBVS058 −JUNE 2005

www.ti.com

8

TYPICAL CHARACTERISTICS (continued)

LONG−TERM STABILITY

(32 Units)

200

150

100

50

0

−50

−100

−150

−200

0400

200

600

800

1000

1200

Time (Hours)

THEORY OF OPERATION

The REF32xx is a family of CMOS, precision bandgap

voltage references. Figure 1 shows the basic bandgap

has a positive temperature coefficient and is forced across

temperature coefficient. The resulting output voltage is

virtually independent of temperature.

V

BANDGAP

Vbe

1

−

+

Vbe

2

−

+

R

1

Q

2

N

Q

Figure 1. Simplified Schematic of Bandgap

Reference

APPLICATION INFORMATION

The REF32xx does not require a load capacitor and is

stable with any capacitive load. Figure 2 shows typical

connections required for operation of the REF32xx. A

supply bypass capacitor of 0.47

µF is recommended.

1

2

3

6

5

4

+2.5V

0.47

µF

+5V

Figure 2. Typical Operating Connections for the

REF3225

SUPPLY VOLTAGE

The REF32xx family of references features an extremely

low dropout voltage. With the exception of the REF3212,

which has a minimum supply requirement of 1.8V, these

references can be operated with a supply of only 5mV

above the output voltage in an unloaded condition. For

loaded conditions, a typical dropout voltage versus load is

shown in the Typical Characteristic curves.