Datasheet

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APPLICATION INFORMATION
Adjustable Version
R
S
LM4041
(Adjustable)
V
S
R1
R2
V
Z
= V
REF

1 
R2
R1

+
V
REF
−
Cathode and Load Currents
R
S


V
S
 V
Z

(
I
L
 I
Z
)
(1)
LM4041
I
Z
+ I
L
I
L
I
Z
V
S
V
Z
R
S
LM4041
PRECISION MICROPOWER SHUNT VOLTAGE REFERENCE
SLCS146E – FEBRUARY 2005 – REVISED FEBRUARY 2006
The adjustable version allows V
Z
to be set by a user-defined resistor divider. The output voltage, V
Z
, is set
according to the equation shown in Figure 14 .
Figure 14. Adjustable Shunt Regulator
In a typical shunt regulator configuration (see Figure 15 ), an external resistor, R
S
, is connected between the
supply and the cathode of the LM4041. R
S
must be set properly, as it sets the total current available to supply
the load (I
L
) and bias the LM4041 (I
Z
). In all cases, I
Z
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 I
L
and minimum V
S
), R
S
must be small enough to supply the minimum I
Z
required for operation of the regulator, as
given by data sheet parameters. At the other extreme, maximum V
S
and minimum I
L
, R
S
must be large enough to
limit I
Z
to less than its maximum recommended rating of 12 mA.
R
S
is calculated as shown in Equation 1 .
Figure 15. Shunt Regulator
15
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