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Zetex Semiconductors |
ADJUSTABLE PRECISION
ZENER SHUNT REGULATOR
ISSUE 2 – FEBRUARY 1997
DEVICE DESCRIPTION
The ZHT431 is a three terminal adjustable
shunt regulator offering excellent
temperature stability and output current
handling capability up to 100mA. The device
offers extended operating temperature
range working from -55 to +125°C. 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.
SCHEMATIC DIAGRAM
V ref
ZHT431
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
• 50µA to 100mA current sink capability
• Low output noise
• Wide temperature range -55 to +125°C
APPLICATIONS
• Series and Shunt regulator
• Voltage monitor
• Over voltage/ under voltage protection
• Switch mode power supplies
VZ
G
nd
4-28
ZHT431
ABSOLUTE MAXIMUM RATING
Cathode Voltage (VZ)
Cathode Current
20V
150mA
Operating Temperature -55 to 125°C
Storage Temperature
-55 to 150°C
Recommended Operating Conditions
Min Max
Cathode Voltage
Vref 20V
Cathode Current
50µA 100mA
Power Dissipation (Tamb=25°C)
(Tjmax = 150°C)
SOT23
330mW
TO92
780mW
SOT223
2W
SO8
SOT89
780mW
1.5W
ELECTRICAL CHARACTERISTICS TEST CONDITIONS (Unless otherwise stated):Tamb=25°C
PARAMETER
VALUE
SYMBOL
MIN
TYP
MAX UNITS
CONDITIONS
Reference Voltage
2% Vref
1%
2.45 2.50 2.55 V
2.475 2.50 2.525
IL=10mA (Fig1), VZ=Vref
Deviation of Reference Input Vdev
Voltage over Temperature
10 30 mV
IL=10mA, VZ=Vref
Ta=full range (Fig1)
Ratio of the change in
Reference Voltage to the
Change in Cathode
Voltage
Reference Input Current
∆Vref
∆VZ
Iref
-1.85 -2.7
-1.0 -2.0
0.12 1.0
mV/V
mV/V
µA
VZ from Vref to 10V
IZ=10mA (Fig2)
VZ from 10V to 20V
IZ=10mA (Fig2)
R1=10k, R2=O/C, lL=10mA
(Fig2)
Deviation of Reference Input ∆Iref
Current over Temperature
0.04 0.2 µA
R1=10k, R2=O/C, IL=10mA
Ta=full range (Fig2)
Minimum Cathode
Current for Regulation
IZmin
35 50 µA
VZ=Vref (Fig1)
Off-state Current
IZoff
0.1 µA
VZ=20V, Vref=0V(Fig3) †
Dynamic Output
Impedance
RZ
0.75 Ω
VZ=Vref (Fig1), f=0Hz,
IC=1mA to 100mA
Deviation of reference input voltage, Vdev, 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, Vref is defined as:
Vmax Vref (ppm⁄ °C)=VdVervefx(T110−0T0020) 0
The dynamic output impedance, Rz, is defined as:
Vmin
Vdev = Vmax - Vmin
RZ
=
∆VZ
∆IZ
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’=Rz (1+RR12)
T1 Temperature
T2
4-29
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