1
www.ptcc.com.tw
AS431
Precision Adjustable Shunt Reference
SEMICONDUCTOR
Features
•Temperature-compensated: 30 ppm/°C
•Trimmed bandgap reference
•Internal amplifier with 150 mA capability
•Multiple temperature ranges
•Low frequency dynamic output
impedance: < 150 mΩ
•Low output noise
•Robust ESD protection
Description
The AS431 is a three-terminal adjustable shunt regulator providing a
highly accurate bandgap reference. The adjustable shunt regulator is
ideal for a wide variety of linear applications that can be implemented
using external components to obtain adjustable currents and voltages.
In the standard shunt configuration, the combination of low temperature
coefficient (TC), sharp turn-on characteristics, low output impedance
and programmable output voltage make this precision reference a per-
fect zener diode replacement.
The AS431 precision adjustable shunt reference is offered in four
bandgap tolerances: ±0.25%, ±0.5%, ±1.0%, and ±2.0%.
CATHODE
TO-92 (LP) 8L SOIC (8D)
ANODE
REFERENCE
CATHODE
REFERENCE
ANODE
ANODE
N/C
CATHODE
ANODE
ANODE
N/C
SOT-89 (S)
5L SOT-23 (5VS)
ANODE
REFERENCE
1
2
3
4
8
7
6
5
ANODE
REFERENCE
N/C
N/C
CATHODE
Circuit Type:
Precision Adjustable
Shunt Regulator
Bandgap Tolerance:
A
C
D
E
Temperature Range:
A = 0°C to 70°C
B = 0°C to 105°C
C = –40°C to +85°C
= ±0.25%
= ±0.5%
= ±1.0%
= ±2.0%
Packaging Option:
A
B
T
M
N
Package Style:
8D
5VS
LP
S
= Ammo Pack
= Bulk
= Tube
= Tape and Reel (7" Reel Dia. SOT-23 Only)
= Tape and Reel (13" Reel Dia.)
= 8 Pin, Plastic SOIC
= 5 Pin, SOT-23
= TO-92
= SOT-89
AS431 - A B 8D N
Pin Configuration – Top View
Ordering Information
2
www.ptcc.com.tw
AS431 Precision Adjustable Shunt Reference
–
+
REFERENCE
(R)
ANODE (A)
CATHODE (K)
2.5 V
Recommended Conditions
Parameter Symbol Rating Unit
Cathode Voltage VKA VREF to 20 V
Cathode Current IK10 mA
Typical Thermal Resistances
Package θJA θJC Typical Derating
TO-92 160°C/W 80°C/W 6.3 mW/°C
SOIC 175°C/W 45°C/W 5.7 mW/°C
SOT-89 110°C/W 8°C/W 9.1 mW/°C
SOT-23/5L 575°C/W 150°C/W 1.7 mW/°C
Absolute Maximum Ratings
Parameter Symbol Rating Units
Cathode-Anode Reverse Breakdown VKA 37 V
Anode-Cathode Forward Current IAK 1A
Operating Cathode Current IKA 250 mA
Reference Input Current IREF 10 mA
Continuous Power at 25°C PD
TO-92 775 mW
8L SOIC 750 mW
SOT-89 1000 mW
5L SOT-23 200 mW
Junction Temperature TJ150 °C
Storage Temperature TSTG –65 to 150 °C
Lead Temperature, Soldering 10 Seconds TL300 °C
Stresses greater than those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent damage to the device. This is a
stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational sec-
tions of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability.
Functional Block Diagram
4
www.ptcc.com.tw
AS431 Precision Adjustable Shunt Reference
Figure 1a. Test Circuit 1 Figure 1b. Test Circuit 2 Figure 1c. Test Circuit 3
0
–10
–20
0.55000
00
015
0.07 mV/°C
0.003%/°C
27 ppm/°C
30 45 60 75 90 105
ppm
mV
%
∆VREF
∆T
Temperature (°C)
• TC in mV/°C =
• TC in %/°C =
∆TA
∆TA
X 100
∆VREF (mV)
VREF at 25°C
∆VREF
• TC in ppm/°C = ∆TA
X 106
VREF at 25°C
∆VREF
R1
R2
IK
VIN VKA
(VREF)IREF
IREF IK
VIN VKA = VREF
IK (OFF)
VIN VKA
Average Temperature Coefficient
Test Circuits
5
www.ptcc.com.tw
AS431Precision Adjustable Shunt Reference
IK – Cathode Current (µA)
900
700
600
500
400
300
200
100
0
–100
–200
800
–1.0 0 1.0
VKA – Cathode Voltage (V)
2.0 3.0
Low Current Operating Characteristics
VKA = VREF
Temperature Range: –55 to 125°C
125°C
25°C
–55°C
IK – Cathode Current (mA)
150
125
100
75
50
25
0
–25
–50
–75
–100–2 –1 0 1 2 3
VKA – Cathode Voltage (V)
High Current Operating Characteristics
VKA = VREF
Temperature Range: –55 to 125°C
IZ off – Off State Cathode Current (nA)
100
10
1
0.1
0.01
–60 –30 0 30
TA – Ambient Temperature (°C)
60 90 120
Off State Leakage
VKA = 36 V
VREF = 0 V
VREF – Reference Voltage (V)
2.56
2.55
2.54
2.53
2.52
2.51
2.50
2.49
2.48
–60 –30 0 30
TA – Ambient Temperature (°C)
60 90 120
VKA = VREF
IK = 10 mA
Temperature Coefficient as a Function of Trim Value
VREF = 2.503 V at 25°C
Figure 4 Figure 5
Figure 2 Figure 3
Typical Performance Curves
6
www.ptcc.com.tw
AS431 Precision Adjustable Shunt Reference
3.0
2.5
2.0
1.5
1.0
0.5
0
–60 –30 0 30 60 90 120
IREF – Reference Input Current (µA)
TA – Ambient Temperature (°C)
Reference Input Current
R1 = 10 kΩ
R2 = ∞
IK =10 mA
0
–10
–20
–30
–40
–500369
VKA – Cathode Voltage (V)
12 15 18 21 24 27 30
VREF – Change in Reference Voltage (mV)
IK = 10 mA
Temperature Range: –55 to 125°C
Reference Voltage Line Regulation
125°C
–55°C
75°C
25°C
0°C
70
60
50
40
30
20
10
0 10 100 1 k
f – Frequency (Hz) 10 k 100 k
Noise Voltage nV/√HZ
VKA = VREF
IK = 10 mA
TA = 25°C
Noise Voltage
ZKA – Dynamic Impedance (Ω)
0.150
0.125
0.100
0.075
0.050
0.025
0.0
–60 –30 0 30
TA – Free Air Temperature
60 90 120
VKA = VREF
IKA = 1 to 100 mA
f ≤ 1 kHz
Low Frequency Dynamic Output Impedance
Typical Performance Curves
Figure 6 Figure 7
Figure 8 Figure 9
7
www.ptcc.com.tw
AS431Precision Adjustable Shunt Reference
100
10
1.0
ZKA – Dynamic Impedance (Ω)
0.1
0.01
1 k 10 k 100 k
f – Frequency (Hz) 1 M 10 M
TA = 25°C
IK = 1 to 100 mA
Dynamic Output Impedance
70
60
50
40
30
20
10
01 k 10 k 100 k 1 M 10 M
f – Frequency (Hz)
230 Ω
IK
AV – Small Signal Voltage Gain (dB)
Temperature Range: –55 to 125°C
IK = 10 mA
OUT
GND
15 k
8.25 k
9 µF
Small Signal Voltage Gain vs. Frequency
Figure 10
Figure 11
Typical Performance Curves
8
www.ptcc.com.tw
AS431 Precision Adjustable Shunt Reference
6
5
4
3
Input and Output Voltages (V)
2
1
0
–1 01234567
t – Time (µs) 891011 12
Input
Output
Pulse Response
INPUT
MONITOR 220 Ω
50 Ω
OUT
GND
fP = 100 kHz
100
90
80
70
60
50
40
30
20
10
0
100101102103
CL – Load Capacitance (pF)
104105106107
150 Ω
CL
10 K
IK
A
C
D
B
TA = 25°C
Stability Boundary Conditions
Stability
Region
IK – Cathode Current (mA)
A: VKA = VREF
B: VKA = 5 V at IK = 10 mA
C: VKA = 10 V at IK = 10 mA
D: VKA = 15 V at IK = 10 mA
Figure 13
Figure 12
Typical Performance Curves
