7.3 Adjustable Version

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 7-3.

RS

LM4041

(Adjustable)

VS

R1

R2

VZ = VREF 1 )

R2

R1

+

VREF

−

Figure 7-3. Adjustable Shunt Regulator

When the output voltage, VZ, is set below 2.5V on adjustable versions of LM4041, the device can experience

increased reference voltage change with output voltage change (ΔVREF/ΔVKA) when compared to output

voltages set equal to or above 2.5V.

7.4 Cathode and Load Currents

In a typical shunt regulator configuration (see Figure 7-4), an external resistor, RS, is connected between the

supply and the cathode of the LM4041. RS must be set properly, this sets the total current available to supply

the load (IL) and bias the LM4041 (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 the maximum recommended rating of 12mA.

RS is calculated as shown in Equation 1.

R

S

+

V

S

* VZ

(I

L

) IZ)

(1)

LM4041

IZ + IL

IL

IZ

VS

VZ

RS

Figure 7-4. Shunt Regulator

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LM4041

SLCS146H – FEBRUARY 2005 – REVISED MARCH 2025

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