TLV431

Issue 1 - June 2008

9

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© Zetex Semiconductors plc 2008

Figure 2. Using the TLV431 as the regulating element in an isolated PSU

Printed circuit board layout considerations

The TLV431 in the SOT23-5 package has the die attached to pin 2, which results in an electrical

contact between pin 2 and pin 5. Therefore, pin 2 of the SOT23-5 package must be left floating or

connected to pin 5. TLV431 in the SC70-6 package has the die attached to pin 2 and 5, which

results in an electrical contact between pins 2, 5 and pin 6. Therefore, pins 2 and 5 must be left

floating or connected to pin 6.

Other applications of TLV431

Figure 3. High current shunt regulator

It may at times be required to shunt-regulate more current than the 15mA that the TLV431 is

capable of.

Figure 3 shows how this can be done using transistor Q1 to amplify the TLV431's current. Care

needs to be taken that the power dissipation and/or SOA requirements of the transistor is not

exceeded

GND

To controller

R1

R2

Optocoupler

To controller

Regulated supply

TLV431

R3

Regulated supply

V OUT

⎟

⎠

⎞

⎜

⎝

⎛ +

=

2

1

1

R

R

V

V

REF

OUT

mA

15

7

.

2

V

3

R

I

7

.

2

V

(max)

OUT

(min)

F

OUT

−

≥

>

−

R3

0.1µF

C1

GND

V

IN

V

OUT

R1

R2

R4

Q1

ZXTP2039F

TLV431

V

REF

⎟

⎠

⎞

⎜

⎝

⎛ +

=

2

1

1

R

R

V

V

REF

OUT

B

BE

OUT

IN

I

V

V

V

R

)

(

3

+

−

=

mA

15

I

h

I

B

(min)

FE

SH

≤

<

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛