September 2, 2010

Adjustable Precision Zener Shunt Regulator

General Description

The LM431 is a 3-terminal adjustable shunt regulator with

guaranteed temperature stability over the entire temperature

range of operation. The output voltage may be set at any level

greater than 2.5V (VREF) up to 36V merely by selecting two

external resistors that act as a voltage divided network. Due

Connection Diagrams

TO-92: Plastic Package

Top View

SO-8: 8-Pin Surface Mount

Top view

0.5% 1% 2%

If Military/Aerospace specified devices are required,

Distributors for availability and specifications.

Wave Soldering (10 sec.) 260°C (lead temp.)

Cathode Voltage 37V

Continuous Cathode Current −10 mA to +150 mA

Reference Voltage −0.5V

Reference Input Current 10 mA

Internal Power Dissipation (Note 2,

Note 3)

TO-92 Package

SO-8 Package

SOT-23 Package

LM431A (Figure 1 )

VZ = VREF, II = 10 mA 2.470 2.495 2.520 V

LM431B (Figure 1 )

VZ = VREF, II = 10 mA 2.485 2.500 2.510 V

LM431C (Figure 1 )

Temperature (Note 4) TA = Full Range (Figure 1 )

Ratio of the Change in Reference Voltage IZ = 10 mA VZ from VREF to 10V −1.4 −2.7 mV/V

to the Change in Cathode Voltage (Figure 2 ) VZ from 10V to 36V −1.0 −2.0

Frequency = 0 Hz (Figure 1 )

VZ = VREF, LM431B, LM431C 0.50 Ω

Frequency = 0 Hz (Figure 1 )

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Electrical specifications do not apply when operating the device

beyond its rated operating conditions.

Note 2: TJ Max = 150°C.

Note 3: Ratings apply to ambient temperature at 25°C. Above this temperature, derate the TO-92 at 6.2 mW/°C, the SO-8 at 6.5 mW/°C, the SOT-23 at 2.2 mW/

Example: VDEV = 8.0 mV, VREF = 2495 mV, T2 − T1 = 70°C, slope is positive.

Note 5: The dynamic output impedance, rZ, is defined as:

When the device is programmed with two external resistors, R1 and R2, (see Figure 2 ), the dynamic output impedance of the overall circuit, rZ, is defined as:

Equivalent Circuit

termine the ranges of stability.

Test Circuit for Curve A Above

Typical Applications

Single Supply Comparator with

Temperature Compensated Threshold