ADJUSTABLE PRECISION
ZENER SHUNT REGULATOR
ISSUE 4 – SEPTEMBER 2000
DEVICE DESCRIPTION
The ZR431 is a three terminal adjustable
s h u n t r e g u l a t o r o ff e r i n g e x ce ll e nt
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
r e q u i r i n g a n i m p r o v e me n t in ze n e r
performance.
ZR431
FEATURES
Surface mount SO8, 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
50 A 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
ref
4-189
78
V
Z
G
nd
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
50 A 100mA
Power Dissipation (T
amb
=25°C,T
jmax
=150°C)
SOT23
330mW
TO92
780mW
SOT223
2W
SO8
780mW
ELECTRICAL CHARACTERISTICS TEST CONDITIONS (Unless otherwise stated):T
amb
=25°C
PARAMETER
Reference Voltage
SYMBOL
2% V
ref
1%
(1)
0.5%
Deviation of Reference Input V
dev
Voltage over Temperature
Dynamic Output Impedance R
Z
(1)
0.75
0.5% SOT23 only.
For definitions of reference voltage temperature coefficient and dynamic output impedance see
NOTES following DC TEST CIRCUITS
4-190
78
Off-state Current
I
Zoff
0.1
Minimum Cathode
Current for Regulation
I
Zmin
35
50
Deviation of Reference
Input Current over
Temperature
I
ref
0.04 0.2
Reference Input Current
I
ref
Ratio of the change in
Reference Voltage to the
Change in Cathode
Voltage
V
ref
V
Z
VALUE
MIN TYP MAX UNITS CONDITIONS
2.45 2.50 2.55 V
2.475 2.50 2.525
2.489 2.50 2.513
8.0
17
mV
mV/V
mV/V
A
A
I
L
=10mA (Fig1), V
Z
=V
ref
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
0.12 1.0
A
A
ZR431
TYPICAL CHARACTERISTICS
160
150
V
ref
=V
Z
I
Z
=10mA
Change in Reference Output Voltage (mV)
0
I
Z
=10mA
Reference Current (nA)
-5
140
130
120
110
100
-40
-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
Change in Vr
ef
v Cathode Voltage
100
34
32
30
28
26
24
-40
-20
0
20
40
60
80
Temperature (°C)
Cathode Current v Temperature
2.506
I
Z
=10mA
2.504
Reference Voltage (V)
2.502
2.500
2.498
2.496
2.494
2.492
2.490
-40
-20
0
20
40
60
80
Temperature (°C)
Reference Voltage v Temperature
4-191
78
Dynamic Impedance ( )
Minimum Cathode Current( A)
V
ref
=V
Z
V
ref
=V
Z
1mA
36
10
10mA
1.0
0.1
100
1k
10k
100k
1M
Frequency (Hz)
Dynamic Impedance v Frequency
SOT223
SO8/TO92
SOT23
ZR431
TYPICAL CHARACTERISTICS
60
Open Loop Voltage Gain (dB)
V
Z
40
9 F
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
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 ( s)
Pulse Response
100
Test Circuit for Pulse Response
Input
150
Cathode Current (mA)
80
STABLE
60
STABLE
40
20
0
Load Capacitance (F)
Stability Boundary Conditions
10p
100p
1000p
0.01
0.1
1
V
ref
< V
Z
< 20, I
Z
= 10mA, T
A
= 25°C
Test Circuit for Stability Boundary Conditions
4-192
78
+
-
V
Z
T
A
= 25°C
V
Z
I
Z
10k
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
R1A
R2A
Vref
High limit = 1 +
Vref
SINGLE SUPPLY COMPARATOR
WITH TEMPERATURE
COMPENSATED THRESHOLD
OVER VOLTAGE / UNDER VOLTAGE
4-193
78
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