Rev. 4/20/01
SPX2431 Precision Adjustable Shunt Regulator
Copyright 2001 Sipex Corporation
1
SPX2431
Precision Adjustable Shunt Regulator
FEATURES
APPLICATIONS
Trimmed Bandgap to 0.5%, and 1%
Battery Operating Equipments
Wide Operating Current........................ 1mA to 100mA
Adjustable Supplies
Extended Temperature Range.................... 0
C to 105
C
Switching Power Supplies
Low Temperature Coefficient .......................30 ppm/
C
Error Amplifiers
Offered in SOT-23-3
Single Supply Amplifier
Replacement for TL431, AS2431
Monitors / VCR / TV
Low Noise Output
Personal Computers
PRODUCT DESCRIPTION
The SPX2431 is a 3-terminal adjustable shunt voltage regulator providing a highly accurate bandgap reference. The SPX2431 acts as
an open-loop error amplifier with a 2.5V temperature compensation reference. The SPX2431s thermal stability, wide operating
current (100mA) and temperature range (0
C to 105
C) makes it suitable for a variety of applications that require a low cost, high
performance solution. SPX2431A tolerance of 0.5% is proven to be sufficient to overcome all of the other errors in the system to
virtually eliminate the need for trimming in the power supply manufacturers assembly lines and contribute a significant cost savings.
The output voltage may be adjusted to any value between V
REF
and 20 volts with two external resistors. In the standard shunt
configuration, the combination of a low temperature coefficient, sharp turn on characteristics, low output impedance, and
programmable output voltage makes this precision reference an excellent error amplifier. The SPX2431 is available in a SOT-23-3
package.
Anode (A)
Cathode (K)
2.5V
Reference
(R)
+
-
Figure 1. Block Diagram
Rev. 4/20/01
SPX2431 Precision Adjustable Shunt Regulator
Copyright 2001 Sipex Corporation
2
SPX2431
ABSOLUTE MAXIMUM RATINGS
PARAMETER
SYMBOL
RATING
UNITS
Cathode-Anode Reverse Breakdown
V
KA
20
V
Anode-Cathode Forward Current, (< 10ms)
I
AK
1
A
Operating Cathode Current
I
KA
100
mA
Reference Input Current
I
REF
1.0
mA
Continuous Power Dissipation at 25
C
SOT-23
P
D
200
mW
Junction Temperature
T
J
150
C
Storage Temperature
T
STG
- 65 to 150
C
Lead Temperature (Soldering 10 sec.)
T
L
300
C
Stresses greater than those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent damage to the device. This is a stress rating only and functional
operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect reliability.
RECOMMENDED CONDITIONS TYPICAL THERMAL RESISTANCES
PARAMETER
SYMBOL
RATING
UNIT
PACKAGE
0
JA
0
JC
TYPICAL DERATING
Cathode Voltage
V
KA
V
REF
to 20
V
SOT-23
575
C/W
150
C/W
1.7 mW/
C
Cathode Current
I
K
10
mA
Typical deratings of the thermal resistances are given for ambient temperature >25
C.
Rev. 4/20/01
SPX2431 Precision Adjustable Shunt Regulator
Copyright 2001 Sipex Corporation
3
SPX2431
ELECTRICAL CHARACTERISTICS
at 25
C I
K
= 10mA V
K
= V
REF
,
unless otherwise specified.
Parameter
Symbol
Test Conditions
Test
Circuit
SPX2431A
SPX2431
Unit
Min
Typ
Max
Min
Typ
Max
Reference Voltage
V
REF
T
J
= 0
C to 105
C
1
1
2.487
2.480
2.500
2.513
2.520
2.474
2.460
2.500
2.526
2.540
V
V
V
REF
with Temp.
TC
1
0.07
0.20
0.07
0.20
mV/
C
Ratio of Change in V
REF
to
Cathode Voltage
V
REF
V
K
V
REF
to 10V
10V to 20V
2
-2.7
-2
-1.01
-0.4
0.3
-2.7
-2.0
-1.01
-0.4
0.3
mV/V
Reference Input Current
I
REF
2
0.7
4
0.7
4
A
I
REF
Temp Deviation
I
REF
T
J
= 0
C to 105
C
2
0.4
1.2
0.4
1.2
A
Min I
K
for Regulation
I
K(MIN)
1
0.4
1
0.4
1
mA
Off State Leakage
I
K(OFF)
V
REF
= 0V,
V
KA
= 20V
3
0.04
0.04
500
nA
Dynamic Output
Impedance
Z
K A
f
Z
= 1kHz
I
K
= 1 to 100mA
1
0.15
0.5
0.15
0.5
Operating Temperature Range (T
J
) = -40
C to 125
C
*see appropriate test circuit (Figure 3)
*CALCULATING AVERAGE TEMPERATURE COEFFICIENT (TC)
T
V
REF
0
15
30
45
60
75
90
105
-10
0.5
5000
0
0
0
0.07 mV/
C
0.003 %/
C
27 ppm/
C
TC in mV/
C =
TC in % /
C =
V
REF
(mV)
T
A
T
A
V
REF
at 25
C
V
REF
x 100
(
)
TC in ppm/
C =
T
A
V
REF
at 25
C
V
REF
x 10
6
(
)
ppm
%
mV
Junction Temperature (
C)
Figure 2. V
REF
vs. Temperature
Rev. 4/20/01
SPX2431 Precision Adjustable Shunt Regulator
Copyright 2001 Sipex Corporation
4
SPX2431
TEST CIRCUITS
V
IN
V
KA
= V
REF
I
REF
I
K
V
IN
V
KA
I
REF
I
K
R1
R2
(V
REF
)
V
IN
V
KA
I
K(OFF)
Figure 3a. Test Circuit for V
KA
= V
REF
Figure 3b. Test Circuit for V
KA
> V
REF
Figure 3c. Test Circuit for I
KOFF
TYPICAL PERFORMANCE CHARACTERISTICS
-2
-1
0
1
2
3
-100
-75
-50
-25
0
25
50
75
100
125
150
I
K
- Cathode Current (mA)
V
KA
- Cathode Voltage (V)
V
KA
= V
REF
Temperature Range: 0
C to 105
C
V
REF
- Reference Voltage (V)
T
A
- Ambient Temperature (
C)
90
120
-60
-30
0
30
60
2.45
2.46
2.47
2.48
2.49
2.50
2.51
2.52
2.53
V
KA
= V
REF
I
K
= 10mA
900
800
700
600
500
400
300
200
100
0
-100
-200
1.0
-1.0
2.0
0
3.0
=
105
C
25
C
-0
C
V
KA
= V
REF
Temperature Range: 0
C to 105
C
V
KA
- Cathode Voltage (V)
I
K
- Cathode Current (
A)
Figure 4. High Current Operating
Figure 5. Reference Voltage vs. Ambient
Figure 6. Low Current Operating
Characteristics
Temperature
Characteristics
Rev. 4/20/01
SPX2431 Precision Adjustable Shunt Regulator
Copyright 2001 Sipex Corporation
5
SPX2431
TYPICAL PERFORMANCE CHARACTERISTICS
30
0
-10
-20
-30
-40
-50
0
3
6
9
12
15
18
21
24
27
125
C
75
C
25
C
0
C
-60
-30
0
30
60
90
120
0
0.5
1.0
1.5
2.0
2.5
3.0
I
REF
- Reference Input Current (
A)
T
A
- Ambient Temperature (
C)
V
REF
(mV)
V
KA
- Cathode Voltage (V)
R1 = 10k
R2 =
I
K
= 10mA
I
KA
= 10mA
Figure 7. Reference Input Current vs. Ambient
Figure 8. Reference Voltage Line Regulation vs. Cathode
Temperature
Voltage and T
AMBIENT
20
10
10
100
1 k
10 k
100 k
0
70
30
40
50
60
-60
-30
0
30
60
90
120
0.0
0.025
0.050
0.075
0.100
0.125
0.150
Noise Voltage nV/
Hz
f - Frequency (Hz)
Z
KA
Dynamic Impedance (
)
T
A
- Free Air Temperature
V
KA
= V
REF
I
K
= 10mA
T
A
= 25
C
V
KA
= V
REF
I
KA
= 1 to 100mA
f
1kHz
Figure 9. Noise Voltage vs. Frequency
Figure 10. Low Frequency Dynamic Output Impedance
vs. T
AMBIENT
Rev. 4/20/01
SPX2431 Precision Adjustable Shunt Regulator
Copyright 2001 Sipex Corporation
6
SPX2431
TYPICAL PERFORMANCE CHARACTERISTICS
10
100
1K
10K
100K
1M
10M
START 10.000Hz
STOP 50 000 000.000Hz
REF LEVEL
60.000dB
0.0deg
/DIV
10.000dB
45.000deg
MARKER 19 422
MAG (A/R)
MARKER 19 422
PHASE (A/R)
611.000Hz
-0.125dB
611.000Hz
46.717deg
GAIN
PHASE
60dB
50dB
40dB
30dB
20dB
10dB
0dB
-10dB
-20dB
-30dB
-40dB
215
180
135
90
45
0
-45
-90
-135
-180
-215
9
F
15k
8.25k
GND
230
I
K
V
IN
V
OUT
Figure 11a. Small Signal Gain and Phase vs. Frequency;
Figure 11b. Test Circuit for Gain and Phase Frequency
T
A
= 25
C
Response
GND
V
OUT
50
f
p
= 100kHz
250
V
IN
Figure 12a. Frequency = 100kHz, I
K
= 10mA, T
A
= 25
C
Figure 12b. Test Circuit for Pulse Response
Rev. 4/20/01
SPX2431 Precision Adjustable Shunt Regulator
Copyright 2001 Sipex Corporation
7
SPX2431
TYPICAL PERFORMANCE CHARACTERISTICS
C
L
- Load Capacitance (pF)
10
7
10
6
10
5
10
4
10
3
10
2
10
1
10
0
0
10
20
30
40
50
60
70
80
90
100
STABLE
T
A
= 25
C
A: V
KA
= V
REF
B: V
KA
= 5V at I
K
= 10 mA
C: V
KA
= 10V at I
K
= 10 mA
D: V
KA
= 15V at I
K
= 10 mA
D
C
A
B
STABLE
I
K
- Cathode Current (mA)
150
10k
I
K
C
L
R
Figure 13a. Stability Boundary Conditions
Figure 13b. Test Circuit for Stability
100
0.1
1.0
10
1 k
10 k
100 k
1 M
0.01
T
A
= 25
C
I
K
= 1 to 100 mA
Z
KA
- Dynamic Impedance (
)
f - Frequency (Hz)
10 M
0.01
0.1
1
10
100
-50
0
50
100
150
T
A
Ambient Temperature (
C)
I
KOFF
Cathode Current (nA)
V
KA
= 20V
V
REF
= 0V
Figure 14. Dynamic Output Impedance T
A
= 25
C,
Figure 15. Off State Leakage
I
K
= 1 to 100mA
Rev. 4/20/01
SPX2431 Precision Adjustable Shunt Regulator
Copyright 2001 Sipex Corporation
8
SPX2431
APPLICATION CIRCUITS
R2
0.1%
V
IN
R3
R1
0.1%
V
OUT
V
REF
SPX2431
Q1
V
IN
R2
R1
0.1%
I
SINK
SPX2431
Figure 16. Shunt Regulator V
OUT
= (1 + R1/R2)V
REF
Figure 17. Constant Current, Sink, I
SINK
= V
REF
/R1
R2
0.1%
R3
R1
0.1%
V
OUT
SPX2431
C2
C1
Isolated
Feedback
V
OUT
RTN
+
R3 sets feedback gain,
C1 provides feedback
compensation
Opto Isolator
V
IN
R1
0.1%
SPX2431
R3
R2
0.1%
C1
R5
R4
V
OUT
Figure 18. Reference Amplifier for Isolated Feedback in
Figure 19. Precision High Current Series Regulator
Off-Line DC-DC Converters
V
OUT
= (1 + R1/R2)V
REF
Rev. 4/20/01
SPX2431 Precision Adjustable Shunt Regulator
Copyright 2001 Sipex Corporation
9
SPX2431
APPLICATION CIRCUITS
V
IN
R1
0.1%
SPX2431
R3
R2
0.1%
Q1
V
OUT
V
CC
R2
SPX2431
V
IN
V
OUT
R1
Figure 20. High Current Shunt Regulator
Figure 21. Single Supply Comparator with Temperature
V
OUT
= (1 + R1/R2)V
REF
Compensated Threshold. V
IN
threshold = 2.5V
*Resistor values are chosen such that the effect of I
REF
is negligible.
Rev. 4/20/01
SPX2431 Precision Adjustable Shunt Regulator
Copyright 2001 Sipex Corporation
10
SPX2431
PACKAGE
SOT-23-3 (M)
3
2
Top View
ANODE
CATHODE
REF
1
ORDERING INFORMATION
Ordering No.
Accuracy
Output Voltage
Package
SPX2431AM
0.5%
2.500V
3-Pin SOT-23
SPX2431M
1.0%
2.500V
3-Pin SOT-23
SIGNAL PROCESSING EXCELLENCE
Sipex Corporation
Headquarters and Main Offices:
22 Linnell Circle
Billerica, MA 01821
TEL: (978) 667-8700
FAX: (978) 670-9001
e-mail: sales@sipex.com
233 South Hillview Drive
Milpitas, CA 95035
TEL: (408) 935-7600
FAX: (408) 934-7500
Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the application or use of any product or circuit described herein;
neither does it convey any license under its patent rights nor the rights of others.
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