ADJUSTABLE PRECISION
ZENER SHUNT REGULATOR
ISSUE 3 DECEMBER 1997
DEVICE DESCRIPTION
The ZR2431 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 25mA. The output
voltage may be set to any chosen voltage
between 1.24 and 15 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.
The ZR2431 is particularly used in the
feedback control loop of switch mode power
supplies. In this application the device 1.24
volt reference enables the generation of low
voltage supplies, typically 3.3 volts or 3 volts.
ZR2431
FEATURES
•
•
•
•
•
•
•
•
•
•
•
•
•
Surface mount SOT23, SOT223, SOT89
and SO8 packages
TO92 package
2.5% and 1% tolerance
Maximum temperature coefficient 52
ppm/°C
Temperature compensated for
operation over the full temperature
range
Programmable output voltage
100µA to 25mA 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
4-154
ZR2431
ABSOLUTE MAXIMUM RATING
Cathode Voltage (V
Z
)
15V
Cathode Current
50mA
Operating Temperature
-40 to 85°C
Storage Temperature
-55 to 125°C
Recommended Operating Conditions
Min Max
Cathode Voltage
V
REF
15V
Cathode Current
100µA 25mA
Power Dissipation (T
amb
=25°C,
T
jmax
=150°C)
SOT23
330mW
SOT223
2W
SO8
780mW
TO92
780mW
SOT89
1.5W
ELECTRICAL CHARACTERISTICS
TEST CONDITIONS (Unless otherwise stated):T
amb
=25°C
PARAMETER
Reference Voltage
VALUE
SYMBOL MIN TYP MAX UNITS CONDITIONS
2.5% V
ref
1.0%
1.209 1.24 1.271 V
1.228 1.24 1.252
4.0
0.5
8.0
2.0
mV
mV/V
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)
R1=10k, R2=O/C, l
L
=10mA (Fig2)
R1=10k, R2=O/C, I
L
=10mA
T
a
=full range (Fig2)
†
V
Z
=15V, V
ref
=0V (Fig3)
V
Z
=V
ref
(Fig1), f=0Hz, I
L
=10mA
Deviation of Reference Input V
dev
Voltage over Temperature
Ratio of the change in
∆
V
ref
Reference Voltage to the
∆
V
Z
Change in Cathode Voltage
Reference Input Current
I
ref
Deviation of Reference Input
∆
I
ref
Current over Temperature
Minimum Cathode
Current for Regulation
Off-state Current
I
Zmin
I
Zoff
0.02 0.11 0.4
0.02 0.2
30
10
100
30
µA
µA
µA
µA
Ω
Dynamic Output Impedance R
Z
0.25 2
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
V
dev
x
1000000
V
ref
(
ppm
⁄
°C
)=
V
ref
(
T1−
T
2)
The dynamic output impedance, Rz, is
∆
V
Z
defined as:
R
Z
=
∆
I
Z
Vmin
When the device is programmed with two
external resistors, R1 and R2, (fig 2) , the
dynamic output impedance of the overall
Vdev = Vmax - Vmin
circuit, R’, is defined as:
R1
R
’
=
R
z
(
1+
)
R2
† With a capacitance of greater than 100pF
between cathode and anode, minimum
cathode current must be 0.2mA.
T1
Temperature
T2
4-155
ZR2431
TYPICAL CHARACTERISTICS
TYPICAL CHARACTERISTICS
Change in Reference Output Voltage(mV)
140
Vref = Vz
2
Iz = 10mA
130
Iz=10mA
1
0
-1
-2
-3
-4
-5
0
5
10
15
Reference Current (nA)
120
110
100
90
80
-40
-20
0
20
40
60
80
Temperature (°C)
Cathode Voltage (V)
Reference Current v Temperature
Minimum Cathode Current(µA)
26
Vref = Vz
Change in V
ref
v Cathode Voltage
10
Vref = Vz
1mA
24
22
20
18
16
14
-40
Dynamic Impedance (Ω)
10mA
1
-20
0
20
40
60
80
0.1
100
1k
10k
100k
Temperature (°C)
Frequency (Hz)
Cathode Current v Temperature
Dynamic Impedance v Frequency
1.244
2.0
Reference Voltage (V)
1.240
1.238
1.236
1.234
1.232
-40
Power Dissipation (W)
1.242
Iz=10mA
SOT 89
SOT 223
1.0
SO8/TO92
SOT23
0
-20
0
20
40
60
80
25
50
75
85
100
Temperature (°C)
Ambient Temprature (°C)
Reference Voltage v Temperature
Power Dissipation Derating
4-156
TYPICAL CHARACTERISTICS
60
Iz = 10mA
ZR2431
V
Z
Open Loop Voltage Gain (dB)
50
40
30
20
10µF
47k
I
Z
240Ω
+
47k
-
10
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
120Ω
2.0
Single
Pulse
Input Monitor
V
Z
Voltage Swing (V)
Vz
1.0
Repetitive
Pulse
0
5.0
2.5
INPUT
Pulse
Generator
50Ω
0
T
A
= 25°C
0
100
200
300
400
500
Time (us)
Test Circuit for Pulse Response
Pulse Response
V
ref
< V
Z
< 20, I
Z
= 10mA, T
A
= 25°C
30
Input
STABLE
150Ω
V
Z
Cathode Current(mA)
25
20
15
STABLE
I
Z
10k
10
5
0
10p
UNSTABLE
100µF
100p
1n
10n
.1µ
1µ
10µ
Load Capacitance(F)
Stablity Boundary Conditions
Test Circuit for Stability
Boundary Conditions
4-157
ZR2431
DC TEST CIRCUITS
Input
I
L
V
Z
Input
I
L
V
Z
Input
V
Z
I
Z
I
ref
1µF
R1
I
Z
I
ref
1µF
I
zoff
1µF
V
ref
R2
V
ref
Fig 1 – Test Circuit for V
z
=V
ref
Fig 2 – Test Circuit for V
z
>V
ref
Fig 3 – Test Circuit for Off
State current
4-158
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