TL4051_15 datasheet(13/24 Pages) TI

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Adjustable Version

TL4051x (Adj)

V = V

(1 + R2/R1)

REF

Cathode and Load Currents

* VZ

) IZ)

(1)

TL4051x12

I + I

TL4051

PRECISION MICROPOWER SHUNT VOLTAGE REFERENCE

SLOS487 – JUNE 2007

APPLICATION INFORMATION (continued)

The adjustable version allows VZ to be set by a user-defined resistor divider. The output voltage, VZ, is set

according to the equation shown in Figure 3.

Figure 3. Adjustable Shunt Regulator

In a typical shunt regulator configuration (see Figure 4), an external resistor, RS, is connected between the

supply and the cathode of the TL4051. RS must be set properly, as it sets the total current available to supply

the load (IL) and bias the TL4051 (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 recommended rating of 12 mA.

RS is calculated as shown in Equation 1.

Figure 4. Shunt Regulator

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