ADJUSTABLE PRECISION
ZENER SHUNT REGULATOR
ISSUE 5 – DECEMBER 2002
DEVICE DESCRIPTION
The ZR431 is a three terminal adjustable
shunt regulator offering excellent
temperature stability and output current
handling capability up to 100mA. The output
voltage may be set to any chosen voltage
between 2.5 and 20 volts by selection of two
external divider resistors.
The devices can be used as a replacement
for zener diodes in many applications
requiring an improvement in zener
performance.
ZR431
FEATURES
•
•
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•
•
•
•
•
•
•
•
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Surface mount SOT223 and SOT23
packages
TO92 package
2%, 1 % and 0.5% tolerance
Max. temperature coefficient 55 ppm/°C
Temperature compensated for operation
over the full temperature range
Programmable output voltage
50µA to 100mA current sink capability
Low output noise
APPLICATIONS
Shunt regulator
Series regulator
Voltage monitor
Over voltage/ under voltage protection
Switch mode power supplies
SCHEMATIC DIAGRAM
V
Z
V
ref
G
nd
4-189
78
ZR431
ABSOLUTE MAXIMUM RATING
Cathode Voltage (V
Z
)
20V
Cathode Current
150mA
Operating Temperature
-40 to 85°C
Storage Temperature
-55 to 125°C
Recommended Operating Conditions
Min
Max
Cathode Voltage
Vref 20V
Cathode Current
50µA 100mA
Power Dissipation (T
amb
=25°C,T
jmax
=150°C)
SOT23
330mW
TO92
780mW
SOT223
2W
ELECTRICAL CHARACTERISTICS TEST CONDITIONS (Unless otherwise stated):T
amb
=25°C
PARAMETER
Reference Voltage
SYMBOL
VALUE
MIN TYP MAX UNITS CONDITIONS
2.45 2.50 2.55 V
2.475 2.50 2.525
2.487 2.50 2.513
8.0
17
mV
mV/V
mV/V
µA
µA
I
L
=10mA (Fig1), V
Z
=V
ref
2% V
ref
1%
(1)
0.5%
Deviation of Reference Input V
dev
Voltage over Temperature
Ratio of the change in
Reference Voltage to the
Change in Cathode
Voltage
Reference Input Current
Deviation of Reference
Input Current over
Temperature
Minimum Cathode
Current for Regulation
Off-state Current
∆V
ref
∆V
Z
I
L
=10mA, V
Z
=V
ref
T
a
=full range (Fig1)
V
Z
from V
ref
to 10V
I
Z
=10mA (Fig2)
V
Z
from 10V to 20V
I
Z
=10mA (Fig2)
R1=10k, R2=O/C, l
L
=10mA
(Fig2)
R1=10k, R2=O/C, I
L
=10mA
T
a
=full range (Fig2)
V
Z
=V
ref
(Fig1)
V
Z
=20V, V
ref
=0V (Fig3)
V
Z
=V
ref
(Fig1), f=0Hz
-1.85 -2.7
-1.0
-2.0
I
ref
∆
I
ref
0.12 1.0
0.04 0.2
I
Zmin
I
Zoff
35
50
0.1
µA
µA
Dynamic Output Impedance R
Z
(1)
0.75
Ω
0.5% SOT23 only.
For definitions of reference voltage temperature coefficient and dynamic output impedance see
NOTES following DC TEST CIRCUITS
4-190
78
ZR431
TYPICAL CHARACTERISTICS
160
150
140
130
120
110
100
-40
V
ref
=V
Z
I
Z
=10mA
Change in Reference Output Voltage (mV)
0
I
Z
=10mA
Reference Current (nA)
-5
-10
-15
-20
-25
0
5
10
15
20
-20
0
20
40
60
80
Temperature (°C)
Cathode Voltage (V)
Reference Current v Temperature
38
36
34
32
30
28
26
24
-40
Change in Vr
ef
v Cathode Voltage
100
Minimum Cathode Current (
m
A)
V
ref
=V
Z
V
ref
=V
Z
1mA
Dynamic Impedance (W )
10
10mA
1.0
-20
0
20
40
60
80
0.1
100
1k
10k
100k
1M
Temperature (°C)
Frequency (Hz)
Cathode Current v Temperature
2.506
I
Z
=10mA
2.504
Dynamic Impedance v Frequency
Reference Voltage (V)
SOT223
2.502
2.500
2.498
2.496
2.494
2.492
2.490
-40
TO92
SOT23
-20
0
20
40
60
80
Temperature (°C)
Reference Voltage v Temperature
4-191
78
4-191
78
ZR431
TYPICAL CHARACTERISTICS
60
Open Loop Voltage Gain (dB)
V
Z
40
9µF
15k
I
Z
230
20
8k25
+
-
0
100
1k
10k
100k
1M
Frequency (Hz)
I
Z
= 10mA,
T
A
= 25°C
Gain v Frequency
Test Circuit for Open Loop Voltage Gain
220
3.0
Repetitive pulse
Input Monitor
V
Z
Voltage Swing (V)
2.0
Single pulse
1.0
V
Z
Pulse
Generator
50
0
5.0
0
0
0.2
0.4
INPUT
0.6
0.8
1.0
Time (µs)
T
A
= 25°C
Pulse Response
100
Test Circuit for Pulse Response
Input
150
V
Z
Cathode Current (mA)
80
STABLE
60
STABLE
I
Z
10k
40
20
0
10p
100p
1000p
0.01µ
0.1µ
1µ
Load Capacitance (F)
V
ref
< V
Z
< 20, I
Z
= 10mA, T
A
= 25°C
Stability Boundary Conditions
Test Circuit for Stability Boundary Conditions
4-192
78
ZR431
APPLICATION CIRCUITS
V+
Vout
V+
Vout
R1
Vref
Vref
R2
R1
R2
Vout = 1 +
R1
R2
Vref
Vout = 1 +
R1
R2
Vref
SHUNT REGULATOR
HIGHER CURRENT SHUNT REGULATOR
V+
ZSR***
In
Out
Common
V+
Vout
30
R1
0.01µF
Vref
R1
R2
Vref
R2
Vout
Vout
MIN
= Vref + Vreg
Vout = 1 +
R1
R2
OUTPUT CONTROL OF A
THREE TERMINAL FIXED REGULATOR
Vref
Vout = 1 +
R1
R2
SERIES REGULATOR
Vref
V+
V+
OUTPUT
INPUT
V
on
V
TH
= 2.5V
2V
R1A
R1B
Vref
OUTPUT
Vref
R2A
R2B
V
off
= V+
Low limit =
1+
R1B
R2B
Vref
High limit = 1 +
R1A
R2A
Vref
SINGLE SUPPLY COMPARATOR
WITH TEMPERATURE
COMPENSATED THRESHOLD
OVER VOLTAGE / UNDER VOLTAGE
4-193
78
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