Adjustable Shunt Regulator
POWER MANAGEMENT
Description
The SC431 is a three terminal adjustable shunt
regulator with thermal stability guaranteed over
temperature. The output voltage can be adjusted to any
value from 2.5V (V
REF
) to 30V with two external
resistors. The SC431 has a typical dynamic output
impedance of 0.25Ω. Active output circuitry provides a
very sharp turn on characteristic, making the SC431 an
excellent replacement for zener diodes.
The SC431 shunt regulator is available with four
voltage tolerances (0.5%, 1.0% and 2.0% over T
A
= -40
°
C
to +85
°
C and 0.5% over T
A
= -40
°
C to +125
°
C) and two
package options (SOT-23-3 and SO-8). This
allows the designer the opportunity to select the
optimum combination of cost and performance for their
application.
SC431
Features
Wide operating current range 130µA to 150mA
Low dynamic output impedance 0.25
Ω
typ.
Trimmed bandgap design + 0.5%
Alternate for TL1431, TL431, LM431 & AS431
Industrial temperature range
Available in SOT-23-3 and SO-8 packages.
Also available in Lead-free, fully WEEE and RoHS
compliant.
Applications
Linear Regulators
Adjustable Supplies
Switching Power Supplies
Battery Operated Computers
Instrumentation
Computer Disk Drives
Typical Application Circuit
(1)(2)
Notes:
1) Set V
OUT
according to the following equation:
R1
V
OUT
=
V
REF
1
+
+
I
REF
R1
R2
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 (130µA) at V
IN(MIN)
.
•
The minimum limit for R should be such that I
Z
does
not exceed 150mA under all load conditions, and the
instantaneous turn-on value for I
Z
does not exceed
200mA. Both of the following conditions must be met:
R
min
≥
V
IN(max)
200mA
(to limit instantaneous turn-on I
Z
)
R
min
≥
I
OUT (min)
+
150mA
(to limit I
Z
under normal
V
IN(max)
−
V
OUT
operating conditions)
Revision: April 23, 2008
1
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SC431
POWER MANAGEMENT
Absolute Maximum Ratings
Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters
specified in the Electrical Characteristics section is not implied.
Parameter
Cathode Voltage
Continous Cathode Current
Reference Input Current
Power Dissipation at T
A
= 25°C
SOT-23-3
SO-8
Thermal Resistance
SOT-23-3
SO-8
Operating Ambient Temperature Range
SC431Cx-.5, SC431Cx-1, SC431Cx-2
SC431CxQ
Operating Junction Temperature Range
Storage Temperature Range
Lead Temperature (Soldering) 10 seconds
ESD Rating (Human Body Model)
Symbol
V
Z
I
Z
I
REF
P
D
Maximum
31
150
10
0.37
0.78
336
163
-40 to +85
-40 to +125
-40 to +150
-65 to +150
300
2
Units
V
mA
mA
W
θ
J A
°C/W
T
A
T
J
T
STG
T
LEAD
V
ESD
°C
°C
°C
°C
kV
Electrical Characteristics
Unless specified:T
A
= 25°C. Values in
bold
apply over full operating ambient temperature range.
SC431Cx-.5,
S C 431C xQ
Parameter
Reference Voltage
V
REF
Temp Deviation
Ratio of Change in
V
REF
to Change in V
Z
Reference Input
Current
I
REF
Temperature
Deviation
Off-State Cathode
Current
Dynamic Output
Impedance
Minimum Operating
Current
2008 Semtech Corp.
SC431Cx-1
Min
2.470
Typ
2.495
8
-0.5
-1.0
0.5
0.4
0.04
0.25
Max
2.520
25
-2.7
-2.0
4
1.2
0.50
0.50
130
µA
µA
µA
Ω
µA
Units
V
mV
mV/V
Symbol
V
REF
V
D EV
Condition
V
Z
= V
REF
, I
Z
= 10mA
(1)
V
Z
= V
REF
, I
Z
= 10mA
(1)
I
Z
= 10mA,
∆V
Z
= 10V to V
REF
I
Z
= 10mA,
∆V
Z
=30V to 10V
R1 = 10k
Ω
, R2 =
∞,
I
Z
= 10mA
(2)
R1 = 10k
Ω
, R2 =
∞,
I
Z
=10mA
(2)
V
REF
= 0V, V
Z
=30V
(3)
f < 1kHz, V
Z
= V
REF
I
Z
= 130µA to 100mA
(1)
V
Z
= V
REF(1)
2
Min
2.482
Typ
2.495
8
-0.5
-1.0
0.5
0.4
0.04
0.25
Max
2.507
17
-2.7
-2.0
4
1.2
0.50
0.50
130
∆
V
REF
∆
V
Z
I
REF
I
REF(DEV)
I
Z (OFF)
r
Z
I
Z (MIN)
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SC431
POWER MANAGEMENT
Electrical Characteristics (Cont.)
Unless specified:T
A
= 25°C. Values in
bold
apply over full operating ambient temperature range.
SC431Cx-2
Parameter
Reference Voltage
V
REF
Temp Deviation
Ratio of Change in V
REF
to
Change in V
Z
Reference Input Current
I
REF
Temperature Deviation
Off-State Cathode Current
Dynamic Output Impedance
Minimum Operating Current
Symbol
V
REF
V
D EV
Condition
V
Z
= V
REF
, I
Z
= 10mA
(1)
V
Z
= V
REF
, I
Z
= 10mA
(1)
I
Z
= 10mA,
∆V
Z
= 10V to V
REF
I
Z
= 10mA,
∆V
Z
=30V to 10V
R1 = 10k
Ω
, R2 =
∞
, I
Z
= 10mA
(2)
R1 = 10k
Ω
, R2 =
∞,
I
Z
=10mA
(2)
V
REF
= 0V, V
Z
=30V
(3)
f < 1kHz, V
Z
= V
REF
, I
Z
= 130µA to 100mA
(1)
V
Z
= V
REF(1)
Min
2.445
Typ
2.495
15
-0.5
-1.0
0.5
0.4
0.04
0.25
Max
2.545
30
-2.7
-2.0
4
1.2
0.50
0.50
130
µA
µA
µA
Ω
µA
Units
V
mV
mV/V
∆
V
REF
∆
V
Z
I
REF
I
REF(DEV)
I
Z (OFF)
r
Z
I
Z (MIN)
Notes:
(1) See Test Circuit 1 below.
(2) See Test Circuit 2 below.
(3) See Test Circuit 3 below.
Test Circuits
Test Circuit 1
V
Z
= V
REF
Test Circuit 2
V
Z
> V
REF
Test Circuit 3
Off-State
Recommended Operating Conditions
Min
Cathode Voltage, V
Z
Cathode Current, I
Z
V
REF
0.130
Max
30
150
Symbol
V
mA
2008 Semtech Corp.
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