ADJUSTABLE PRECISION
ZENER SHUNT REGULATOR
ISSUE 3 – MARCH 1998
ZR431
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.
FEATURES
•Surface mount SO8, SOT89, SOT223
and SOT23 packages
•TO92 package
•2% and 1 % 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
VZ
Gnd
Vref
SCHEMATIC DIAGRAM
4-189
ZR431
ABSOLUTE MAXIMUM RATING
Cathode Voltage (VZ) 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 (Tamb=25°C,Tjmax=150°C)
SOT23 330mW
TO92 780mW
SOT223 2W
SO8 780mW
SOT89 1.5W
ELECTRICAL CHARACTERISTICS TEST CONDITIONS (Unless otherwise stated):Tamb=25°C
PARAMETER SYMBOL VALUE
UNITS CONDITIONS
MIN TYP MAX
Reference Voltage 2%
1%
Vref 2.45
2.475
2.50
2.50
2.55
2.525
VI
L=10mA (Fig1), VZ=Vref
Deviation of Reference Input
Voltage over Temperature
Vdev 8.0 17 mV IL=10mA, VZ=Vref
Ta=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 VZ from Vref to 10V
IZ=10mA (Fig2)
-1.0 -2.0 mV/V VZ from 10V to 20V
IZ=10mA (Fig2)
Reference Input Current Iref 0.12 1.0 µAR1=10k, R2=O/C, lL=10mA
(Fig2)
Deviation of Reference
Input Current over
Temperature
∆
I
ref
0.04 0.2 µAR1=10k, R2=O/C, IL=10mA
Ta=full range (Fig2)
Minimum Cathode
Current for Regulation
IZmin 35 50 µAVZ=Vref (Fig1)
Off-state Current IZoff 0.1 µAVZ=20V, Vref =0V (Fig3)
Dynamic Output Impedance RZ0.75 ΩVZ=Vref (Fig1), f=0Hz
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:
V
ref
(
ppm
⁄ °
C
)=
V
dev
x
1000000
V
ref
(
T
1−
T
2)
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+
R
1
R
2)
Vmax
Vmin
T1 T2
Vdev = Vmax - Vmin
Temperature
4-190
ZR431
TYPICAL CHA RACTERISTICS
Cathode Current v Temperature Dynamic Impedance v Frequency
Frequency (Hz)
100
10
1.0
0.1
100 1k 10k 100k 1M
Dynamic Impedance (Ω)
Temperature (°C)
Minimum Cathode Current(µA)
24-40 0 20 40 60-20 80
26
28
30
32
34
36
38 Vref=VZ
Reference Current v Temperature
Temperature (°C)
Reference Voltage (V)
100
-40 0 20 40 60-20 80
110
120
130
140
150
160
2.490
2.492
2.494
2.496
2.498
2.500
2.502
2.504
2.506
Reference Current (nA)
-40 0 20 40 60-20 80
Reference Voltage v Temperature
Temperature (°C)
IZ=10mA
Vref=VZ
IZ=10mA
Change in V ref v Cathode Voltage
Cathode Voltage (V)
0
-25
Change in Reference Output Voltage (mV)
5101520
-20
-15
-10
-5
0 IZ=10mA
Vref=VZ
10mA
1mA
Power Dissipation Derating
Ambient Temperature (°C)
50 10075
Power Dissipation (W)
0
1.0
25
2.0
85
SOT 223
SO8/TO92
SOT23
SOT 89
4-191
ZR431
TYPICAL CHARACTERISTICS
Gain v Frequency
Frequency (Hz)
Load Capacitance (F)
Stability Boundary Conditions
Time (µs)
Pulse Response
IZ
15k
VZ
Test Circuit for Open Loop Voltage Gain
8k25
9µF
230
+
-
IZ = 10mA, TA= 25°C
Test Circuit for Stability Boundary Conditions
Input 150
10k
Vref < VZ< 20, IZ= 10mA, TA= 25°C
VZ
IZ
Input Monitor VZ
Test Circuit for Pulse Response
220
50
Pulse
Generator
TA= 25°C
60
40
20
0100 1k 10k 100k 1M
Open Loop Voltage Gain (dB)
Voltage Swing (V)
2.0
0
0 0.4 0.6 0.8 1.00.2
1.0
0
5.0
3.0 Repetitive pulse
Single pulse VZ
INPUT
STABLESTABLE
010p
20
40
60
80
100
100p 1000p 0.01µ0.1µ1µ
Cathode Current (mA)
4-192
APPLICATION CIRCUITS
ZR431
R2
Vout = 1 + R1
R2 Vref
SERIES REGULATOR
V+
Vout
R1
30
0.01µF
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
4-193
IL
Input
Fig 1 – Test Circuit for Vz=Vref
DC TEST CIRCUITS
Fig 2 – Test Circuit for Vz>Vref
Input V
I
Z
zoff
Fig 3 – Test Circuit for Off
State current
ZR431
4-194
ZR431
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
Part Number Package Tol.
%
Part Mark
ZR431C01 TO92 1.0 ZR43101
ZR431C TO92 2.0 ZR431
ZR431G01 SOT223 1.0 ZR43101
ZR431G SOT223 2.0 ZR431
ZR431F01 SOT23 1.0 43B
ZR431F SOT23 2.0 43A
ZR431Z01 SOT89 1.0 43D
ZR431Z SOT89 2.0 43C
ZR431N801 SO8 1.0 ZR43101
ZR431N8 SO8 2.0 ZR431
ORDERING INFORMATION
4-195
