ADJUSTABLE PRECISION
ZENER SHUNT REGULATOR
Issue 2 - February 1998
DEVICE DESCRIPTION
The ZH431 is a three terminal adjustable
s hu n t r e g u l a t or o f f e r i n g e xc el l e nt
temperature stability and output current
handling capability up to 30mA. The output
voltage may be set to any chosen voltage
between 2.5 and 36 volts by selection of two
external divider resistors.
The devices can be used as a replacement
for zener diodes in many applications
r e qu i r i n g a n i mpr o ve me nt i n z e ner
performance.They are also ideal for use in
the feedback circuits of off line SMPUs as
well as many general purpose regulator and
reference applications where initial accuracy
and low temperature coefficient are key
requirements.
Note:
ZH431 is not recommended for new designs.
Refer to ZR431
ZH431
FEATURES
•
•
•
•
•
•
•
•
•
•
•
•
•
Surface mount SO8, SOT223,SOT23
and SOT89 packages
TO92 package
2% and 1% tolerance
Maximum temperature coefficient 55
ppm/°C
Temperature compensated for
operation over the full temperature
range
Programmable output voltage
50µA to 30mA 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
4-15
ZH431
ABSOLUTE MAXIMUM RATING
Cathode Voltage (V
Z
)
40V
Cathode Current
50mA
Operating Temperature
-40 to 85°C
Storage Temperature
-55 to 125°C
Recommended Operating Conditions
Min Max
Cathode Voltage
Vref 36V
Cathode Current
50µA 30mA
Power Dissipation (T
amb
=25°C, T
jmax
=150°C)
SOT23
330mW
TO92
780mW
SOT223
2W
SO8
780mW
SOT89
1.5W
ELECTRICAL CHARACTERISTICS TEST CONDITIONS (Unless otherwise
stated):T
amb
=25°C
PARAMETER
Reference Voltage
Deviation of Reference
Input 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
SYMBOL
VALUE
MIN
TYP MAX UNITS CONDITIONS
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 36V
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
=V
ref
(Fig1), f=0Hz
2.45 2.50 2.55 V
2.475 2.50 2.525
8.0
17
mV
2% V
ref
1%
V
dev
∆
V
ref
∆
V
Z
-0.7 -2.7
-0.6 -2.0
mV/V
mV/V
µA
µA
I
ref
∆
I
ref
0.15 1.0
0.06 0.2
I
Zmin
21
50
0.75
µA
Ω
Dynamic Output Impedance R
Z
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:
Vmax
Vmin
Vdev = Vmax - Vmin
V
dev
x
1000000
V
ref
(
T1−T2)
The dynamic output impedance, Rz, is defined as:
∆
V
Z
R
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:
R1
R
’
=
R
z
(
1+
)
R2
V
ref
(
ppm
⁄
°C
)=
T2
T1
Temperature
4-16
ZH431
TYPICAL CHARACTERISTICS
200
Vref= Vz
Iz= 10mA
5
Change in Reference Voltage (mV)
Reference Current (nA)
180
160
140
0
-5
-10
-15
-20
-25
0
5
10
15
20
25
30
35
40
120
100
-40
-20
0
20
40
60
80
Temperature (°C)
Cathode Voltage (V)
Reference Current v Temperature
26
Vref= Vz
Change in Vref v Cathode Voltage
100
1mA
Minimum Cathode Current (uA)
24
22
20
18
16
14
12
-40
Dynamic Impedance (Ohms)
10
Vref=Vz
10mA
1
0.1
-20
0
20
40
60
80
0.01
100
1k
10k
100k
1M
Temperature (°C)
Frequency (Hz)
Cathode Current v Temperature
2.52
Iz= 10mA
Dynamic Impedance v Frequency
2.0
2.51
Reference Voltage (V)
Power Dissipation (W)
SOT223
2.50
2.49
1.0
SOT89
S08/T092
SOT23
2.48
2.47
-40
-20
0
20
40
60
80
0
25
50
75
100
Temperature (°C)
Ambient Temperature (°C)
Reference Voltage v Temperature
Power Dissipation Derating
4-17
ZH431
TYPICAL CHARACTERISTICS
70
60
50
V
Z
15k
9µF
I
Z
230Ω
Open Loop Gain (dB)
40
+
30
20
10
0
100
8k25
-
1k
10k
100k
1M
Frequency (Hz)
I
Z
= 10mA,
T
A
= 25°C
Gain v Frequency
Test Circuit for Open Loop Voltage Gain
220Ω
V
Z
Input Monitor
3.0
REPETITIVE
PULSE
2.0
Voltage Swing (V)
SINGLE
PULSE
1.0
Pulse
Generator
50Ω
0
5
INPUT
0
0
0.05
0.1
0.15
0.2
0.25
T
A
= 25°C
Time (µs)
Pulse Response
Test Circuit for Pulse Response
Input
150
V
Z
30
25
I
Z
Unstable
Cathode Current (mA)
20
Stable
10k
15
10
5
Stable
0
10p
100p
1000p
0.01µ
0.1µ
1µ
Load Capacitance (F)
Stability Boundary Conditions
V
ref
< V
Z
< 40, I
Z
= 10mA, T
A
= 25°C
Test Circuit for Stability Boundary Conditions
4-18
ZH431
DC TEST CIRCUITS
I
L
Input
Fig 1 – Test Circuit for V
z
=V
ref
Fig 2 – Test Circuit for V
z
>V
ref
4-19
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