TL4050 Datasheet, PDF (17/35 Pages) Texas Instruments – PRECISION MICROPOWER SHUNT VOLTAGE REFERENCE

TL4050
www.ti.com........................................................................................................................................................ SLOS486A – JUNE 2007 – REVISED AUGUST 2009
Cathode and Load Currents
In a typical shunt-regulator configuration (see Figure 3), an external resistor, R_S, is connected between the
supply and the cathode of the TL4050. R_S must be set properly, as it sets the total current available to supply the
load (I_L) and bias the TL4050 (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-rated value of 15 mA.
R_S is calculated according to Equation 1:
R_S
+
ǒ_VS
(I_L
*
)
V_Z^Ǔ
I_Z)
(1)
V_S
R_S
V_Z
TL4050
I_Z + I_L
I_L
I_Z
Figure 3. Shunt Regulator
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