AT431
Low-Voltage Adjustable Precision
Shunt Regulator
Features
˙Low-Voltage
Operation: Down to 1.24V
˙1%
Reference-Voltage Tolerance
˙Adjustable
Output Voltage, Vo=Vref to 12V
˙Low
Operational Cathode Current….50μA
˙0.25Ω
Typical Output Impedance
˙SOT-23-3
, SOT-23-5 and TO-92 Packages
Description
The AT431 is low-voltage three-terminal
adjustable voltage reference with specified
thermal stability over applicable commercial
temperature ranges. Output voltage may be set to
any value between Vref (1.24V) and 12V with
two external resistors (see Figure 2).
When used with an optocoupler, the AT431 is
ideal voltage reference in isolated feedback
circuits for 1.8V to 12 V switching-mode power
supplies. This device has typical output
impedance of 0.20Ω. Active output circuitry
provides a very sharp turn-on characteristic,
making the AT431 excellent replacements for
low-voltage zener diodes in many applications,
including onboard regulation and adjustable
power supplies.
Application
˙Linear Regulators
˙Voltage Reference for Power Circuit
Block Diagram and Symbol
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
WWW:
http://www.aimtron.com.tw
Fax: 886-3-563-0879
Email:
service@aimtron.com.tw
1
AT431
Low-Voltage Adjustable Precision
Shunt Regulator
Equivalent Schematic
Pin Assignments
Ordering Information
Part number
AT431Z
AT431X
AT431UN
AT431UT
AT431C
Package
TO-92
SOT-25
SOT-23
SOT-23
SOT-89
Marking
Z
X
N
T
C
*
: Data Code
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
WWW:
http://www.aimtron.com.tw
Fax: 886-3-563-0879
Email:
service@aimtron.com.tw
2
AT431
Low-Voltage Adjustable Precision
Shunt Regulator
Absolute maximum ratings (TA = 25
o
C)
Parameter
Cathode voltage
Continuous cathode current range
Reference Current
Operating temperature
Storage temperature
Package thermal impedance
θ
JA
Symbol
VKA
IK
IREF
T
OPR
T
STG
SOT-23-5
SOT-23-3
TO-92
PD
Limits
12
-20~20
-0.05~3
-30~+85
-55~+150
347
156
(TJ(max)-TA)/
θ
JA
unit
V
mA
mA
o
C
o
C
o
C/W
Power Dissipation
Stresses beyond those listed under “ absolute maximum ratings” may cause permanent damage to the
device. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
Recommend operating condtion
Parameter
Cathode voltage VKA
Continuous cathode current range IK
Operating free-air temperature range T
A
min
Vref
0.05
0
Max
12
15
70
unit
V
mA
o
C
Electrical characteristics (
unless otherwise noted
)
Parameter
Reference Voltage
Symbol
Vref (
TA = 25
o
C
)
Vref (
TA = full
o
range 0~70
C)
Vref(dev)
∆
Vref /∆ VKA
Iref
Iref(dev)
IK(min)
IK(off)
| ZKA |
Min.
1.228
1.221
-
-
-
-
-
-
-
Typ.
1.24
-
4
-1.5
0.15
0.05
40
0.001
0.20
Max.
1.252
1.259
20
-2.7
0.5
0.3
50
0.1
0.4
Unit
V
V
mV
Conditions
VKA= Vref
(Figure 1)
IK=10mA
Vref deviation over full
temperature range
Ratio of Vref change in
cathode voltage change
Reference terminal
current
Iref deviation over full
temperature range
Minimum cathode current
for regulation
Off-state cathode current
Dynamic impedance
VKA= Vref
IK=10mA
(Figure 1)
mV/V VKA= Vref to 12V
IK=10mA
(Figure 2)
µA
IK=10mA
(Figure 2)
R1=10KΩ
µA
IK=10mA R1=10KΩ
(Figure 2)
R2=open
µA
VKA= Vref
(Figure 1)
µA
Ω
VKA=12V
Vref =0V
(Figure 3)
VKA= Vref f≤1KHz
IK=0.1mA to 15mA
(Figure 1)
* The dynamic impedance is defined as :
|ZKA| =
∆
VKA /∆ IKA
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
WWW:
http://www.aimtron.com.tw
Fax: 886-3-563-0879
Email:
service@aimtron.com.tw
3
AT431
Low-Voltage Adjustable Precision
Shunt Regulator
Parameter Measurement Information
Figure 1. Test Circuit for VKA=Vref
VO= VKA=Vref
Figure 2. Test Circuit for VKA>Vref
VO= VKA=Vref *(1+R1/R2)+Iref *R1
Figure 3. Test Circuit for IK(off)
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
WWW:
http://www.aimtron.com.tw
Fax: 886-3-563-0879
Email:
service@aimtron.com.tw
4
AT431
Low-Voltage Adjustable Precision
Shunt Regulator
Figure 4.
Figure 5.
Figure 6.
Figure 7.
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
WWW:
http://www.aimtron.com.tw
Fax: 886-3-563-0879
Email:
service@aimtron.com.tw
5
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