TLV431ACDBVT datasheet(21/46 Pages) TI1

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REF

CATHODE

ANODE

VSUP

RSUP

(

Vref

0.1%

TL431

= 1 +

Vref

)

TLV431, TLV431A, TLV431B

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SLVS139V – JULY 1996 – REVISED JANUARY 2015

10.2.2 Shunt Regulator/Reference

Figure 26. Shunt Regulator Schematic

10.2.2.1 Design Requirements

For this design example, use the parameters listed in Table 2 as the input parameters.

Table 2. Design Parameters

DESIGN PARAMETER

EXAMPLE VALUE

Reference Initial Accuracy

1.0%

Supply Voltage

6 V

Cathode Current (Ik)

1 mA

Output Voltage Level

1.24 V - 6 V

Load Capacitance

100 nF

Feedback Resistor Values and Accuracy (R1 & R2)

10 k

10.2.2.2 Detailed Design Procedure

When using TLV431 as a Shunt Regulator, determine the following:

•

Input voltage range

•

Temperature range

•

Total accuracy

•

Cathode current

•

Reference initial accuracy

•

Output capacitance

10.2.2.2.1

Programming Output/Cathode Voltage

In order to program the cathode voltage to a regulated voltage a resistive bridge must be shunted between the

cathode and anode pins with the mid point tied to the reference pin. This can be seen in Figure 26, with R1 & R2

being the resistive bridge. The cathode/output voltage in the shunt regulator configuration can be approximated

by the equation shown in Figure 26. The cathode voltage can be more accuratel determined by taking in to

account the cathode current:

VO=(1+R1/R2)*Vref–Iref*R1

In order for this equation to be valid, TLV431 must be fully biased so that it has enough open loop gain to

mitigate any gain error. This can be done by meeting the Imin spec denoted in Recommended Operating

Conditions table.

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