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TL431 Datasheet, PDF (6/11 Pages) Motorola, Inc – PROGRAMMABLE PRECISION REFERENCES | |||
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PROGRAMMABLE PRECISION SHUNT REGULATOR TL431/A/C
The deviation parameters ÎVREF/ÎT and ÎIREF/ÎT are defined as the differences between the maximum and
minimum values obtained over the recommended temperature range. The average full-range temperature
coefficient of the reference voltage, αVREF, is defined as :
Where :
ÎTA is the recommended operating free-air temperature range of the device.
αVREF can be positive or negative, depending on whether minimum VREF or maximum VREF, respectively, occurs at
the lower temperature.
Example : Maximum VREF=2496mV at 30â, maximum VREF=2492mV at 0â, VREF=2495mV at 25â,
ÎTA=70â for TL431C.
ââ 4mV ââ Ã106
aVREF
= â 2495mV â
70°C
â 23 ppm
°C
Because minimum VREF occurs at the lower temperature, the coefficient is positive.
Calculating Dynamic Impedance
The dynamic impedance is defined as :
Z KA
= ÎVKA
ÎI KA
When the device is operating with two external resistors, the total dynamic impedance of the circuit is given by :
Z'
=
ÎV
ÎI
â
Z KA
ââ1 + R1 ââ
â R2 â
2008 â Rev. 1.2
-6-
HTC
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