LM4431 datasheet(4/8 Pages) NSC

4 / 8 page

Functional Block Diagram

Applications Information

The LM4431 is a micro-power curvature-corrected 2.5V

bandgap shunt voltage reference. For space critical applica-

tions, the LM4431 is available in the sub-miniature SOT-23

surface-mount package. The LM4431 has been designed for

stable operation without the need of an external capacitor

connected between the “+” pin and the “−” pin. If, however, a

bypass capacitor is used, the LM4431 remains stable. The

operating current range is 100 µA to 15 mA.

The LM4431’s SOT-23 package has a parasitic Schottky di-

ode between pin 2 (−) and pin 3 (Die attach interface con-

tact). Therefore, pin 3 of the SOT-23 package must be left

floating or connected to pin 2.

In a conventional shunt regulator application (

Figure 1),an

external series resistor (R

S) is connected between the sup-

ply voltage and the LM4431. R

S determines the current that

flows through the load (I

L) and the LM4431 (IQ). Since load

current and supply voltage may vary, R

S should be small

enough to supply at least the minimum acceptable I

Q to the

LM4431 even when the supply voltage is at its minimum and

the load current is at its maximum value. When the supply

voltage is at its maximum and I

L is at its minimum, RS should

be large enough so that the current flowing through the

LM4431 is less than 15 mA.

S is determined by the supply voltage, (VS), the load and

operating current, (I

L and IQ), and the LM4431’s reverse

breakdown voltage, V

Typical Applications

DS011374-8

DS011374-9

FIGURE 1. Shunt Regulator

LM4431 Datasheet(PDF) 4 Page - National Semiconductor (TI)