ADJUSTABLE PRECISION
ZENER SHUNT REGULATOR
ISSUE 2 FEBRUARY 1997
DEVICE DESCRIPTION
The ZHT431 is a three terminal adjustable
s h u n t r e g u l a t o r o f f e r i n g e x c e l l e n t
temperature stability and output current
handling capability up to 100mA. The device
offers extended operating temperature
range working from -55 to +125C. 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 i n z e n e r
performance.
FEATURES
Surface mount SO8, SOT89, SOT223
and SOT23 packages
TO92 package
2% and 1% tolerance
Maximum temperature coefficient 67
ppm/C
Temperature compensated for
operation over the full temperature
range
Programmable output voltage
50
A to 100mA current sink capability
Low output noise
Wide temperature range -55 to +125C
APPLICATIONS
Series and Shunt regulator
Voltage monitor
Over voltage/ under voltage protection
Switch mode power supplies
ZHT431
V
Z
G
nd
V
ref
SCHEMATIC DIAGRAM
4-28
ZHT431
ABSOLUTE MAXIMUM RATING
Cathode Voltage (V
Z
)
20V
Cathode Current
150mA
Operating Temperature
-55 to 125C
Storage Temperature
-55 to 150C
Recommended Operating Conditions
Min
Max
Cathode Voltage
Vref
20V
Cathode Current
50
A
100mA
Power Dissipation (T
amb
=25C)
(T
jmax
= 150C)
SOT23
330mW
TO92
780mW
SOT223
2W
SO8
780mW
SOT89
1.5W
ELECTRICAL CHARACTERISTICS TEST CONDITIONS (Unless otherwise stated):T
amb
=25C
PARAMETER
SYMBOL
VALUE
UNITS CONDITIONS
MIN
TYP MAX
Reference Voltage 2%
1%
V
ref
2.45
2.475
2.50
2.50
2.55
2.525
V
I
L
=10mA (Fig1), V
Z
=V
ref
Deviation of Reference Input
Voltage over Temperature
V
dev
10
30
mV
I
L
=10mA, V
Z
=V
ref
T
a
=full range (Fig1)
Ratio of the change in
Reference Voltage to the
Change in Cathode
Voltage
V
ref
V
Z
-1.85 -2.7
mV/V
V
Z
from V
ref
to 10V
I
Z
=10mA (Fig2)
-1.0
-2.0
mV/V
V
Z
from 10V to 20V
I
Z
=10mA (Fig2)
Reference Input Current
I
ref
0.12 1.0
A
R1=10k, R2=O/C, l
L
=10mA
(Fig2)
Deviation of Reference Input
Current over Temperature
I
ref
0.04 0.2
A
R1=10k, R2=O/C, I
L
=10mA
T
a
=full range (Fig2)
Minimum Cathode
Current for Regulation
I
Zmin
35
50
A
V
Z
=V
ref
(Fig1)
Off-state Current
I
Zoff
0.1
A
V
Z
=20V, V
ref
=0V(Fig3)
Dynamic Output
Impedance
R
Z
0.75
V
Z
=V
ref
(Fig1), f=0Hz,
I
C
=1mA to 100mA
Deviation of reference input voltage, V
dev,
is defined as the maximum variation of the reference
input voltage over the full temperature range.
The average temperature coefficient of the reference input voltage, V
ref
is
defined
as:
V
ref
(
ppm
/
C
)=
V
dev
x 1000000
V
ref
(
T1
-
T2
)
The dynamic output impedance, Rz, is defined as:
R
Z
=
V
Z
I
Z
When the device is programmed with two external
resistors, R1 and R2, (fig 2) , the dynamic output
impedance of the overall circuit, R', is defined as:
R
'
=
R
z
(
1
+
R1
R2
)
Vmax
Vmin
T1
T2
Vdev = Vmax - Vmin
Temperature
4-29
ZHT431
TYPICAL CHARACTERISTICS
Dynamic Impedance v Frequency
Frequency (Hz)
100
10
1.0
0.1
100
1k
10k
100k
1M
Dyn
amic Imped
a
n
ce
(
)
Change in V
r
ef
v Cathode Voltage
Cathode Voltage (V)
0
-25
Cha
n
g
e in
R
e
ferenc
e Ou
t
p
u
t
V
o
lt
age
(mV
)
5
10
15
20
-20
-15
-10
-5
0
I
Z
=10mA
V
ref
=V
Z
10mA
1mA
170
90
100
110
120
130
140
150
160
-50 -25
0
25
50
75 100 125
Temperature ( C)
I
ref
vs. Temperature
Refe
r
e
n
ce C
u
r
r
e
n
t
(n
A)
40
-50 -25
0
25
50
75 100 125
Temperature ( C)
I
zmin
vs. Temperature
28
26
24
30
32
34
36
38
Min
im
u
m
Cath
o
d
e
C
u
r
rent
(
A)
Power Dissipation Derating
0
150
50
100
125
0
0.2
1.0
1.2
2.0
P
o
wer
Dis
sip
a
t
i
o
n
(
W
)
Ambient Temperature ( C)
SOT223
TO92
25
75
SO8/
SOT23
0.4
0.6
0.8
1.4
1.6
1.8
2.486
2.488
2.490
2.492
2.494
2.496
2.498
2.500
2.502
-50
-25
0
25
50
75 100 125
Temperature ( C)
Refe
r
e
n
ce V
o
ltag
e
(
V
)
V
ref
vs. Temperature
SOT89
4-30
ZHT431
TYPICAL CHARACTERISTICS
Gain v Frequency
Frequency (Hz)
Load Capacitance (F)
Stability Boundary Conditions
Time (
s)
Pulse Response
I
Z
15k
V
Z
Test Circuit for Open Loop Voltage Gain
8k25
9
F
230
+
-
I
Z
= 10mA,
T
A
= 25C
Test Circuit for Stability Boundary Conditions
Input
150
10k
V
ref
< V
Z
< 20, I
Z
= 10mA, T
A
= 25C
V
Z
I
Z
Input Monitor
V
Z
Test Circuit for Pulse Response
220
50
Pulse
Generator
T
A
= 25C
60
40
20
0
100
1k
10k
100k
1M
O
pen L
o
o
p
V
oltage
G
ain (dB)
V
oltage Swing
(
V
)
2.0
0
0
0.4
0.6
0.8
1.0
0.2
1.0
0
5.0
3.0
Repetitive pulse
Single pulse
V
Z
INPUT
STABLE
STABLE
0
10p
20
40
60
80
100
100p
1000p
0.01
0.1
1
Ca
t
hode Current (mA)
4-31
I
L
Input
Fig 1 Test Circuit for V
z
=V
ref
DC TEST CIRCUITS
Fig 2 Test Circuit for V
z
>V
ref
ZHT431
Input
V
I
Z
zoff
Fig 3 Test Circuit for Off
State current
NOTE
Since the "Off State" disables all internal circuitry including leakage control, operating in this
mode at high temperature is not recommended.
4-32
APPLICATION CIRCUITS
ZHT431
R2
Vout = 1 +
R1
R2
Vref
SERIES REGULATOR
V+
Vout
R1
30
0.01F
Vref
Vout = 1 +
R1
R2
Vref
Vout = Vref + Vreg
MIN
OUTPUT CONTROL OF A
THREE TERMINAL FIXED REGULATOR
R2
R1
V+
Vout
Vref
ZSR***
In
Out
Common
R2
R1
V+
Vout
Vout =
Vref
1 +
R1
R2
Vref
HIGHER CURRENT SHUNT REGULATOR
V+
OUTPUT
INPUT
V
= 2.5V
TH
V
2V
on
V
= V+
off
SINGLE SUPPLY COMPARATOR
WITH TEMPERATURE
COMPENSATED THRESHOLD
R2A
R1A
V+
Vref
R2B
R1B
Vref
1 +
R1B
R2B
Vref
OVER VOLTAGE / UNDER VOLTAGE
PROTECTION CIRCUIT
Low limit =
High limit =
1 +
R1A
R2A
Vref
R2
R1
Vout =
Vref
1 +
R1
R2
Vref
SHUNT REGULATOR
V+
Vout
OUTPUT
4-33
TO92 Package Suffix C
Bottom
View
CONNECTION DIAGRAMS
SO8 Package Suffix N8
Top
View
SOT223 Package
Suffix G
Top
View
Pin 4 floating or connected to pin 2
SOT23 Package
Suffix F
Top
View
SOT89 Package Suffix Z
Top
View
Pin 4 floating or connected to pin 2
ORDERING INFORMATION
ZHT431
PART No
TOL
%
PACKAGE PARTMARK
ZHT431N802
2
SO8
ZHT43102
ZHT431N801
1
SO8
ZHT43101
ZHT431G02
2
SOT223
ZHT43102
ZHT431G01
1
SOT223
ZHT43101
ZHT431F02
2
SOT23
43D
ZHT431F01
1
SOT23
43C
ZHT431C02
2
TO92
ZHT43102
ZHT431C01
1
TO92
ZHT43101
ZHT431Z02
2
SOT89
43F
ZHT431Z01
1
SOT89
43E
4-34
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