POWER MANAGEMENT
1
www.semtech.com
SC431L
Low Voltage Adjustable
Shunt Regulator
Description
Features
Revision 6, June 2003
The SC431L is a three terminal adjustable shunt
regulator with thermal stability guaranteed over
temperature. The output voltage can be adjusted to any
value from 1.24V (V
REF
) to 20V with two external
resistors. The SC431L has a typical dynamic output
impedance of 0.05
. Active output circuitry provides a
very sharp turn on characteristic, making the SC431L an
excellent replacement for zener diodes.
The SC431L shunt regulator is available with four volt-
age tolerances (0.25%, 0.5%, 1.0% and 2.0%), two
operating temperature ranges (commercial and indus-
trial) and two package options (SOT-23-3 and SOT-23-
5). This allows the designer the opportunity to select the
optimum combination of cost and performance for their
application.
Linear Regulators
Adjustable Supplies
Switching Power Supplies
Battery Operated Computers
Instrumentation
Computer Disk Drives
Low voltage operation (down to 1.24V)
Wide operating current range 100A to 100mA
Low dynamic output impedance 0.05
typ.
Trimmed bandgap design 0.25%
Upgrade for TLV431A
Available in SOT-23-3 and SOT-23-5 packages
Notes:
1) Set V
OUT
according to the following equation:
1
R
I
2
R
1
R
1
V
V
REF
REF
OUT
+
+
=
2) Choose the value for R as follows:
The maximum limit for R should be such that the
cathode current, I
Z
, is greater than the minimum
operating current (100A) at V
IN(MIN)
.
The minimum limit for R should be such that I
Z
does
not exceed 100mA under all load conditions, and the
instantaneous turn-on value for I
Z
does not exceed
150mA. Both of the following conditions must be met:
mA
150
V
R
(max)
IN
min
(to limit instantaneous turn-on I
Z
)
mA
100
I
V
V
R
(min)
OUT
OUT
(max)
IN
min
+
-
(to limit I
Z
under normal
operating conditions)
Applications
Typical Application Circuit
(1)(2)
3
2003 Semtech Corp.
www.semtech.com
POWER MANAGEMENT
SC431L
%
1
L
1
3
4
C
S
%
2
L
1
3
4
C
S
r
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t
e
m
a
r
a
P
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o
b
m
y
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e
g
a
tl
o
V
e
c
n
e
r
e
f
e
R
V
F
E
R
V
Z
V
=
F
E
R
I
,
Z
A
m
0
1
=
)
1
(
8
2
2
.
1
0
4
2
.
1
2
5
2
.
1
5
1
2
.
1
0
4
2
.
1
5
6
2
.
1
V
5
1
2
.
1
5
6
2
.
1
0
0
2
.
1
0
8
2
.
1
V
F
E
R
n
o
it
a
i
v
e
D
p
m
e
T
V
V
E
D
V
Z
V
=
F
E
R
, I
Z
A
m
0
1
=
)
1
(
0
1
5
2
0
1
5
3
V
m
n
i
e
g
n
a
h
C
f
o
o
it
a
R
I
Z
,
A
m
0
1
=
V
Z
V
o
t
V
6
1
=
F
E
R
0
.
1
-
7
.
2
-
0
.
1
-
7
.
2
-
V
/
V
m
V
F
E
R
V
n
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C
o
t
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t
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p
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r
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f
e
R
t
n
e
r
r
u
C
I
F
E
R
k
0
1
=
1
R
=
2
R
,
,
I
Z
A
m
0
1
=
)
2
(
5
1
.
0
5
.
0
5
1
.
0
5
.
0
A
I
F
E
R
e
r
u
t
a
r
e
p
m
e
T
n
o
it
a
i
v
e
D
I
)
V
E
D
(
F
E
R
k
0
1
=
1
R
=
2
R
,
,
I
Z
A
m
0
1
=
)
2
(
1
.
0
4
.
0
1
.
0
4
.
0
A
e
d
o
h
t
a
C
e
t
a
t
S
-
ff
O
I
)
F
F
O
(
Z
V
F
E
R
V
,
V
0
=
Z
V
6
=
)
3
(
5
2
1
.
0
0
5
1
.
0
5
2
1
.
0
0
5
1
.
0
A
t
n
e
r
r
u
C
V
F
E
R
V
,
V
0
=
Z
V
6
1
=
)
3
(
5
3
1
.
0
0
5
1
.
0
5
3
1
.
0
0
5
1
.
0
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u
p
t
u
O
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a
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y
D
e
c
n
a
d
e
p
m
I
r
Z
V
,
z
H
k
1
<
f
Z
V
=
F
E
R
I
Z
A
m
0
0
1
o
t
A
0
0
1
=
)
1
(
5
0
.
0
5
1
.
0
5
0
.
0
5
1
.
0
g
n
it
a
r
e
p
O
m
u
m
i
n
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t
n
e
r
r
u
C
I
)
N
I
M
(
Z
V
Z
V
=
F
E
R
)
1
(
0
2
0
0
1
0
2
0
0
1
A
Electrical Characteristics (Cont.)
Z
REF
V
V
Unless specified:T
A
= 25C. Values in bold apply over full operating ambient temperature range.
)
2
e
g
a
p
m
o
r
f
d
e
u
n
i
t
n
o
C
(
%
5
2
.
0
L
1
3
4
C
S
%
5
.
0
L
1
3
4
C
S
r
e
t
e
m
a
r
a
P
l
o
b
m
y
S
n
o
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t
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d
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o
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t
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c
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a
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D
e
c
n
a
d
e
p
m
I
r
Z
V
,
z
H
k
1
<
f
Z
V
=
F
E
R
I
Z
A
m
0
0
1
o
t
A
0
0
1
=
)
1
(
5
0
.
0
5
1
.
0
5
0
.
0
5
1
.
0
g
n
it
a
r
e
p
O
m
u
m
i
n
i
M
t
n
e
r
r
u
C
I
)
N
I
M
(
Z
V
Z
V
=
F
E
R
)
1
(
0
2
0
0
1
0
2
0
0
1
A
Notes:
(1) See Test Circuit 1 on page 4.
(2) See Test Circuit 2 on page 4.
(3) See Test Circuit 3 on page 4.
n
i
M
x
a
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l
o
b
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V
,
e
g
a
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d
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V
F
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R
6
1
V
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,t
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e
r
r
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C
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d
o
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t
a
C
Z
A
0
0
1
0
0
1
A
m
Recommended Operating Conditions
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