LM4040C30ILPR datasheet(28/51 Pages) VISHAY

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Cathode and Load Currents

* VZ

) IZ)

(1)

LM4040

IZ + IL

LM4040

PRECISION MICROPOWER SHUNT VOLTAGE REFERENCE

SLOS456J – JANUARY 2005 – REVISED SEPTEMBER 2006

APPLICATION INFORMATION (continued)

In a typical shunt-regulator configuration (see Figure 9), an external resistor, RS, is connected between the

supply and the cathode of the LM4040. RS must be set properly, as it sets the total current available to supply

the load (IL) and bias the LM4040 (IZ). In all cases, IZ must stay within a specified range for proper operation of

the reference. Taking into consideration one extreme in the variation of the load and supply voltage (maximum IL

and minimum VS), RS must be small enough to supply the minimum IZ required for operation of the regulator, as

given by data-sheet parameters. At the other extreme, maximum VS and minimum IL, RS must be large enough

to limit IZ to less than its maximum-rated value of 15 mA.

RS is calculated according to Equation 1:

Figure 9. Shunt Regulator

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