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RC0431A (RC431A)
Low-Voltage Adjustable Precision Shunt Regulator
Features
•
•
•
•
•
•
Low voltage operation to 1.24V
1% reference voltage tolerance
Output voltage adjustable from V
ref
to 12V
Low 80µA operational cathode current
0.25Ω typical output impedance
TO-92, SOT23-3 and SOT23-5 packages
Description
The RC0431A is a low-voltage 3-terminal adjustable
precision voltage reference regulator. It has an excellent
thermal stability over the standard commercial temperature
range. The output voltage can be set to any value between
Vref (1.24V) and 12V using two external resistors. The
RC0431A operates from a lower voltage (1.24V) than the
traditional shunt regulator references which operate from
2.5V. When used with an optocoupler, the RC0431A will be
an ideal voltage reference in an isolated feedback circuit for
use in switched-mode power supplies and modular DC-DC
converters. The RC0431A has a low output impedance of
active output circuitry offering a very sharp turn-on
characteristic. The RC0431A will be an excellent
replacement for low-voltage zener diodes in many
applications such as on-board regulation and adjustable
power supplies.
Applications
• Voltage reference for discrete power circuits
Symbol
REF
Anode
Cathode
65-431A-01
Block Diagram
CATHODE
REF
+
_
V
ref
= 1.24V
65-431A-02
ANODE
REV. 1.0.7 8/5/03
RC0431A (RC431A)
PRODUCT SPECIFICATION
Pin Assignments
SOT-23 PACKAGE (3-Lead)
(TOP VIEW)
REF
1
3
CATHODE
2
ANODE
SOT-23 PACKAGE (5-Lead)
(TOP VIEW)
NC
NC
CATHODE
1
2
3
4
REF
5
ANODE
TO-92 PACKAGE
(TOP VIEW)
CATHODE
ANODE
REF
65-431A-03
NC = No internal connection
Equivalent Schematic
CATHODE
REF
A
ANODE
65-431A-04
Absolute Maximum Ratings
Ratings are over full operating free-air temperature range unless otherwise noted.
Cathode voltage, V
KA
Continuous cathode current I
K
Reference current, I
ref
Power dissipation
Storage temperature range
13.2V
–20mA to 20mA
–0.05mA to 3mA
See Dissipation Rating Table
-65° to 150°C
Notes:
1. Functional operation under these conditions is not implied. Permanent damage may occur if the device is subjected to
conditions outside these ratings.
Recommended Operating Conditions
Parameter
Cathode voltage, V
KA
Cathode current, I
K
Operating temperature range in free-air, T
A
Min.
V
REF
0.1
0
Max.
12
15
70
Units
V
mA
°C
2
REV. 1.0.7 8/5/03
PRODUCT SPECIFICATION
RC0431A (RC431A)
Dissipation Rating Table
Package
TO-92
SOT23-5
Power Rating
TA
≤
25°C
775mW
150mW
Derating Factor
TA
≥
25°C
6.2mW/
O
C
1.2mW/
o
C
Power Rating
TA = 70°C
496mW
96mW
Electrical Specifications
T
A
= 25°C (unless otherwise noted), at free-air
Symbol
V
ref
Parameters
Reference Voltage
Conditions
V
KA
= V
ref
, T
A
= 25°C
I
K
= 10mA,
T
A
= 0 to 70°C
V
ref (dev)
∆V
ref
∆V
KA
I
ref
V
ref
deviation over full temperature
range (see note 2)
Ratio of V
ref
change in cathode
voltage change
Reference terminal current
V
KA
= V
ref
, I
K
= 10mA,
See note 2 and Figure 1.
I
K
= 10mA,
∆V
KA
= V
ref
to 6V.
See figure 2.
I
K
= 10mA,
R1 = 10KΩ, R2 =
∞
See figure 2.
I
K
= 10mA,
R1 = 10KΩ, R2 =
∞
See note 1 & figure 2.
V
KA
= V
ref
See figure 1.
V
KA
= 6V, V
ref
= 0
See figure 3.
V
KA
= V
ref
, f
≤
1KHz
I
K
= 0.1mA to 15mA,
See figure 1.
Min.
1.228
1.221
4
-1.5
Typ.
1.24
Max.
1.252
1.259
12
-2.7
mV
mV
V
µA
Units
V
0.15
0.5
I
ref(dev)
I
ref
deviation over full temperature
range (see note 2)
Minimum cathode current for
regulation
Off-state cathode current
Dynamic impedance (see note 3)
0.05
0.3
µA
I
K(min)
I
off
|Z
KA
|
55
0.001
0.25
80
0.1
0.4
µA
µA
Ω
Notes:
1. Functional operation under these conditions is not implied. Permanent damage may occur if the device is subjected to
conditions outside these ratings.
2. Full temperature range is 0°C to 70°C.
3. The deviation parameters V
ref(dev)
and I
ref(dev)
are defined as the differences between the maximum and minimum values
obtained over the rated temperature range. The average full-range temperature coefficient of the reference input voltage,
∞V
ref
, is defined as:
∞V
ref
{
V
ref
(
dev
)
⁄
V
ref
〈
T
A
=
25°C
〉 } ×
10
-
〈
ppm/°C
〉
= ---------------------------------------------------------------------------------------------
∆T
A
6
where
∆T
A
is the rated operating free-air temperature range of the device.
∞V
ref
can be positive or negative depending on whether minimum V
ref
or maximum V
ref
, respectively, occurs at the lower
temperature.
4. The dynamic impedance is defined as:
Z
KA
= ∆V
KA
/
∆I
K
When the device is operating with two external resistors (see Figure 2), the total dynamic impedance of the circuit is given
by:
R
1
∆V
Z
KA
= -------
≈
Z
KA
×
1 + ------
-
-
R
2
∆I
REV. 1.0.7 8/5/03
3
RC0431A (RC431A)
PRODUCT SPECIFICATION
Parameter Measurement Information
V
IN
V
IN
I
K
V
OUT
R1
I
ref
I
K
V
OUT
R2
V
ref
65-431A-05
V
ref
65-431A-06
Figure 1. Test Circuit for
V
KA
= V
REF
, V
OUT
= V
KA
= V
REF
Figure 2. Test Circuit for
V
KA
> V
REF
, V
OUT
= V
KA
= V
REF
x (1+R1/R2) + I
REF
x R1
V
IN
V
OUT
I
OFF
65-431A-07
Figure 3. Test Circuit for I
OFF
Iref–Reference Input Current (nA)
Vref–Reference Voltage (V)
1.250
1.246
1.242
1.238
lk = 10 mA
lk = 10 mA, R1 = 10 kΩ, R2 = infinite
250
200
150
100
50
–40
1.230
–40 –20
0
20
40
60
80
100
–20
0
20
40
60
80
100
Tj—Junction Temp. (°C)
Tj—Junction Temp. (°C)
Figure 4. Reference Voltage vs. Junction Temp.
Figure 5. Reference Input Current vs. Junction Temp.
V
KA
= Vref, T = 25°C
150
120
90
60
30
0
–30
–60
–90
–120
–150
–1
0
–0.5
15
V
KA
= Vref, T = 25°C
lk–Cathode Current (mA)
10
5
0
–5
–10
–15
-1
–0.5
0
0.5
1
1.5
V
KA
–Cathode Voltage (V)
lk–Cathode Current (µA)
0.5
1
1.5
V
KA
–Cathode Voltage (V)
Figure 7. Cathode Current vs. Cathode Voltage
Figure 6. Cathode Current vs. Cathode Voltage
4
REV. 1.0.7 8/5/03
PRODUCT SPECIFICATION
RC0431A (RC431A)
Ioff–Off State Cathode Current (nA)
40.0
30.0
20.0
10.0
Del Vref / Del Vka (mV/V)
V
KA
= 6V, Vref = 0V
1.4
1.2
1.0
0.8
0.6
0.4
0.2
lk = 10 mA, Del V
KA
= Vref to 6V
0.0
–40
–20
0
20
40
60
80
100
0.0
–40
–20
0
20
40
60
80
100
Tj—Junction Temperature (°C)
Tj—Junction Temperature (°C)
Figure 8. Off-State Cathode Current vs.
Junction Temperature
100
|Zka|–Reference Impedance (Ω)
Figure 9. Ratio of Delta Reference Voltage
to Delta Cathode Voltage vs. Junction Temperature
10
1
100Ω
OUTPUT
I
K
100Ω
+
0.1
0.01
1000
10000
100000
f–Frequency (Hz)
1000000
10000000
GND
Figure 10. Reference Impedance vs. Frequency
Figure 11. Test Circuit for Reference Impedance
REV. 1.0.7 8/5/03
5
