Tlv431 – Diodes TLV431 User Manual
Page 10
TLV431
Document number: DS32088 Rev. 6 - 2
10 of 14
October 2012
© Diodes Incorporated
TLV431
A Product Line of
Diodes Incorporated
Application Notes
(cont.)
Printed Circuit Board Layout Considerations (cont.)
⎟
⎠
⎞
⎜
⎝
⎛ +
=
2
R
1
R
1
V
V
REF
OUT
B
BE
OUT
IN
I
)
V
V
(
V
3
R
+
−
=
mA
18
I
h
I
B
(min)
FE
(max)
OUT
≤
<
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
(max)
OUT
REF
S
I
V
R
=
Figure 5. Series Regulator with Current Limit
Figure 5 adds current limit to the series regulator in Figure 4 using a second TLV431. For currents below the limit, the circuit works normally
supplying the required load current at the design voltage. However should attempts be made to exceed the design current set by the second
TLV431, the device begins to shunt current away from the base of Q1. This begins to reduce the output voltage and thus ensuring that the output
current is clamped at the design value. Subject only to Q1’s ability to withstand the resulting power dissipation, the circuit can withstand either a
brief or indefinite short circuit.
⎟
⎠
⎞
⎜
⎝
⎛ +
=
2
R
1
R
1
V
V
REF
OUT
)
V
V
(
V
REF
REG
OUT
+
≥
(All features of the regulator
such as short circuit protection,
thermal shutdown, etc, are
maintained.)
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.