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RA0431
Low-Voltage Adjustable Precision Shunt Regulator
Features
Description
•
•
•
•
•
•
The RA0431 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 RA0431 operates
from a lower voltage (1.24V) than the traditional shunt regulator references which operate from 2.5V. When used with an
optocoupler, the RA0431 will be an ideal voltage reference
in an isolated feedback circuit for use in switched-mode
power supplies and modular DC-DC converters. The
RA0431 has a low output impedance of active output
circuitry offering a very sharp turn-on characteristic.
The RA0431 will be an excellent replacement for lowvoltage zener diodes in many applications such as on-board
regulation and adjustable power supplies.
Low voltage operation to 1.24V
1% reference voltage tolerance
Output voltage adjustable from Vref to 12V
Low 80µA operational cathode current
0.25Ω typical output impedance
SOT23-5 package
Applications
• Voltage reference for discrete power circuits
Symbol
Block Diagram
REF
Anode
CATHODE
Cathode
65-431A-01
REF
+
_
Vref = 1.24V
65-431A-02
ANODE
Rev. 1.0.1
RA0431A
PRODUCT SPECIFICATION
Pin Assignments
SOT-23 PACKAGE
(TOP VIEW)
NC
1
NC
2
CATHODE
3
5
ANODE
4
REF
NC = No internal connection
65-431A-03
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, VKA
13.2V
Continuous cathode current IK
–20mA to 20mA
Reference current, Iref
–0.05mA to 3mA
Power dissipation
See Dissipation Rating Table
Storage temperature range
-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
Min.
Max.
Cathode voltage, VKA
VREF
12
V
0.1
15
mA
0
70
°C
Cathode current, IK
Operating temperature range in free-air, TA
2
Units
PRODUCT SPECIFICATION
RA0431A
Dissipation Rating Table
Package
SOT23-5
Power Rating
TA ≤ 25°C
Derating Factor
TA ≥ 25°C
Power Rating
TA = 70°C
150mW
1.2mW/oC
96mW
Electrical Specifications
TA = 25°C (unless otherwise noted), at free-air
Symbol
Vref
Parameters
Reference Voltage
Conditions
Min.
Typ.
Max.
Units
VKA = Vref, TA = 25°C
1.228
1.24
1.252
V
IK = 10mA,
TA = 0 to 70°C
1.221
Vref (dev)
Vref deviation over full temperature
range (see note 2)
VKA = Vref, IK = 10mA,
See note 2 and Figure 1.
∆Vref
∆VKA
Ratio of Vref change in cathode
voltage change
Iref
1.259
4
12
mV
IK = 10mA,
∆VKA = Vref to 6V.
See figure 2.
-1.5
-2.7
mV
V
Reference terminal current
IK = 10mA,
R1 = 10KΩ, R2 = ∞
See figure 2.
0.15
0.5
µA
Iref(dev)
Iref deviation over full temperature
range (see note 2)
IK = 10mA,
R1 = 10KΩ, R2 = ∞
See note 1 & figure 2.
0.05
0.3
µA
IK(min)
Minimum cathode current for
regulation
VKA = Vref
See figure 1.
55
80
µA
Ioff
Off-state cathode current
VKA = 6V, Vref = 0
See figure 3.
0.001
0.1
µA
|ZKA|
Dynamic impedance (see note 3)
VKA = Vref, f ≤ 1KHz
IK = 0.1mA to 15mA,
See figure 1.
0.25
0.4
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 Vref(dev) and Iref(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,
∞Vref, is defined as:
6
∞V ref
{ V ref ( dev ) ⁄ V ref 〈 T A = 25°C〉 } × 10
〈 ppm/°C〉 = ---------------------------------------------------------------------------------------------∆T A
where ∆TA is the rated operating free-air temperature range of the device.
∞Vref can be positive or negative depending on whether minimum Vref or maximum Vref, respectively, occurs at the lower
temperature.
4. The dynamic impedance is defined as: ZKA= ∆VKA/ ∆IK
When the device is operating with two external resistors (see Figure 2), the total dynamic impedance of the circuit is given
by:
R1
∆V
Z KA = -------- ≈ Z KA × 1 + -------
R 2
∆I
3
RA0431A
PRODUCT SPECIFICATION
Parameter Measurement Information
V OUT
V IN
VIN
VOUT
IK
IK
R1
R2
Iref
V ref
V ref
65-431A-06
65-431A-05
Figure 1. Test Circuit for
VKA = VREF, VOUT = VKA = VREF
Figure 2. Test Circuit for
VKA > VREF, VOUT = VKA = VREF x (1+R1/R2) + IREF x R1
VOUT
V IN
I OFF
65-431A-07
1.250
Iref–Reference Input Current (nA)
Vref–Reference Voltage (V)
Figure 3. Test Circuit for IOFF
lk = 10 mA
1.246
1.242
1.238
1.230
–40 –20
0
20
40
60
80
100
Tj—Junction Temp. (°C)
100
50
–40
–20
10
5
0
–5
–15
-1
–0.5
0
0.5
0
20
40
60
80
100
Figure 5. Reference Input Current vs. Junction Temp.
lk–Cathode Current (µA)
lk–Cathode Current (mA)
150
VKA = Vref, T = 25°C
–10
1
1.5
VKA–Cathode Voltage (V)
Figure 6. Cathode Current vs. Cathode Voltage
4
200
Tj—Junction Temp. (°C)
Figure 4. Reference Voltage vs. Junction Temp.
15
lk = 10 mA, R1 = 10 kΩ, R2 = infinite
250
VKA = Vref, T = 25°C
150
120
90
60
30
0
–30
–60
–90
–120
–150
–1
–0.5
0
0.5
1
1.5
VKA–Cathode Voltage (V)
Figure 7. Cathode Current vs. Cathode Voltage
40.0
RA0431A
VKA = 6V, Vref = 0V
Del Vref / Del Vka (mV/V)
Ioff–Off State Cathode Current (nA)
PRODUCT SPECIFICATION
30.0
20.0
10.0
0.0
–40
–20
0
20
40
60
80
100
Tj—Junction Temperature (°C)
1.4
lk = 10 mA, Del VKA = Vref to 6V
1.2
1.0
0.8
0.6
0.4
0.2
0.0
–40
–20
0
20
40
60
80
100
Tj—Junction Temperature (°C)
Figure 8. Off-State Cathode Current vs.
Junction Temperature
Figure 9. Ratio of Delta Reference Voltage
to Delta Cathode Voltage vs. Junction Temperature
|Zka|–Reference Impedance (Ω)
100
10
100Ω
1
OUTPUT
IK
0.1
100Ω
+
0.01
1000
10000
100000
1000000
10000000
GND
f–Frequency (Hz)
Figure 10. Reference Impedance vs. Frequency
Figure 11. Test Circuit for Reference Impedance
5
PRODUCT SPECIFICATION
RA0431A
Mechanical Dimensions (continued)
SOT23-5 Package
Inches
Symbol
A
A1
B
c
D
E
e
e1
H
L
α
Millimeters
Min.
Max.
Min.
Max.
.170
.014
.008
.003
.106
.059
.195
.020
.90
.00
.20
.08
2.70
1.50
1.45
.15
.020
.010
.122
.071
.037 BSC
.075 BSC
.087
.126
.004
.024
0°
10°
Notes:
Notes
1. Package outline exclusive of mold flash & metal burr.
2. Package outline exclusive of solder plating.
3. EIAJ Ref Number SC-74A.
.50
.25
3.10
1.80
.95 BSC
1.90 BSC
2.20
3.20
.10
.60
0°
10°
e
B
L
E
H
e1
c
D
A
A1
6
PRODUCT SPECIFICATION
RA0431A
Notes:
7
RA0431A
PRODUCT SPECIFICATION
Ordering Information
Product Number
Package
RA0431M
SOT23-5
DISCLAIMER
FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY
PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY
LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER
DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS.
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FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES
OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR
CORPORATION. As used herein:
1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the body,
or (b) support or sustain life, or (c) whose failure to perform
when properly used in accordance with instructions for use
provided in the labeling, can be reasonably expected to
result in significant injury to the user.
2. A critical component is any component of a life support
device or system whose failure to perform can be
reasonably expected to cause the failure of the life support
device or system, or to affect its safety or effectiveness.
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1998 Fairchild Semiconductor Corporation