TLV431

Issue 1 - June 2008

11

www.zetex.com

© Zetex Semiconductors plc 2008

Figure 6. Increasing output voltage of a fixed linear regulator

One of the useful applications of the TLV431 is in using it to improve the accuracy and/or extend

the range and flexibility of fixed voltage regulators. In the circuit in Figure 6 above, both the

output voltage and its accuracy are entirely determined by the TLV431, R1 and R2. However the

rest of the features of the regulator (up to 5A output current, output current limiting and thermal

shutdown) are all still available.

Figure 7. Adjustable linear voltage regulator

Figure 7 is similar to Figure 6 with adjustability added. Note the addition of R3. This is only

required for the AP1117 due to the fact that its ground or adjustment pin can only supply a few

micro-Amps of current at best. R3 is therefore needed to provide sufficient bias current for the

TLV431.

(All features of the regulator such

as short circuit protection,

thermal shutdown, etc, are

maintained.)

(All features of the regulator such as short

circuit protection, thermal shutdown, etc,

are maintained.)

GND

V

IN

V

OUT

AP1084

Volt Reg

GND

R2

TLV431

R1

V

IN

V

OUT

0.1µF

C1

V

REF

⎟

⎠

⎞

⎜

⎝

⎛ +

=

2

1

1

R

R

V

V

REF

OUT

)

(

REF

REG

OUT

V

V

V

+

≥

GND

Vin

Vout

VR1

AP1117

GND

R2

TLV431

V

IN

V

OUT

0.1µF

C1

R3

R1

V

REF

1.2V

I

B

⎟

⎠

⎞

⎜

⎝

⎛ +

=

2

1

1

R

R

V

V

REF

OUT

)

(

REF

REG

OUT

V

V

V

+

≥

B

REG

OUT

IN

I

V

V

V

R

)

(

3

−

−

=

mA

I

mA

B

15

1

.

0

≤

≤