1

2

3

6

5

4

+2.5V

0.47

F

µ

+5V

110

108

106

104

102

100

98

96

94

1.5

2.0

3.0

4.0

2.5

3.5

4.5

6.0

5.0

5.5

Power Supply (V)

REF3212-EP, REF3220-EP, REF3225-EP

REF3230-EP, REF3233-EP, REF3240-EP

www.ti.com

SBVS078B

– OCTOBER 2006 – REVISED AUGUST 2011

APPLICATION INFORMATION

The REF32xx does not require a load capacitor and is stable with most capacitive loads, see Load Capacitance

Guidelines. Figure 4 shows typical connections required for operation of the REF32xx. A supply bypass capacitor

of 0.47

μF is recommended.

Figure 4. 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 1.8 V, these references can be operated with a supply of

only 5 mV above the output voltage in an unloaded condition. For loaded conditions, a typical dropout voltage

versus load is shown in the Typical Characteristic curves.

The REF32xx also features a low quiescent current of 100

μA, with a maximum quiescent current over

temperature of just 135

μA. The quiescent current typically changes less than 2 μA over the entire supply range,

as shown in Figure 5.

Figure 5. Supply Current vs Supply Voltage

Supply voltages below the specified levels can cause the REF32xx to momentarily draw currents greater than

the typical quiescent current. This momentary current draw can be prevented by using a power supply with a fast

rising edge and low output impedance.

For optimal startup when the IN pin and ENABLE pin are tied together, keep the input voltage rise time less than

or equal to 2ms. For rise times greater than 2ms, the ENABLE pin must be kept below 0.7V until the voltage at

the IN pin has reached the minimum operating voltage. One way to control the voltage at the ENABLE pin is with

an additional RC filter, such as that shown in Figure 6. The RC filter must hold the voltage at the ENABLE pin

below the threshold voltage until the voltage at the input pin has reached the minimum operating voltage.

Copyright

© 2006–2011, Texas Instruments Incorporated

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Product Folder Link(s): REF3212-EP, REF3220-EP, REF3225-EP REF3230-EP, REF3233-EP, REF3240-EP