®
SPX2431
Precision Adjustable Shunt Regulator
FEATURES
■
Trimmed Bandgap to 0.5% and 1.0%
■
Wide Operating Current 1mA to 100mA
■
Extended Temp. Range: 0°C to 105°C
■
Low Temperature Coefficient 30 ppm/°C
■
Offered in 3 Pin SOT-23 (M)
■
Replacement for TL431, AS2431
■
Low Noise Output
APPLICATIONS
■
Battery Operating Equipment
■
Adjustable Supplies
■
Switching Power Supplies
■
■
■
■
ANODE
3
SPX2431
3 Pin SOT-23
1
REF
Top View
2
CATHODE
Now Available in Lead Free Packaging
Error Amplifiers
Single Supply Amplifier
Monitors / VCRs / TVs
Personal Computers
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 SPX2431’s 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 manufacturer's assembly line 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 SOT-23-3
package.
FUNCTIONAL DIAGRAM
Cathode (K)
Reference
(R)
+
-
2.5V
Anode (A)
Date: 1/19/05
SPX2431 Precision Adjustable Shunt Regulator
© Copyright 2005 Sipex Corporation
1
ABSOLUTE MAXIMUM RATINGS
Cathode-Anode Reverse Breakdown V
KA
....................................... 20V
Anode-Cathode Forward Current, (<10ms) I
AK
................................. 1A
Operating Cathode Current I
KA
.................................................. 100mA
Reference Input Current I
REF
....................................................... 1.0mA
Continuos Power Dissipation at 25°C P
D
SOT-23 .................................................................. 200 mW
Junction Temperature T
J
........................................................... 150
°C
Storage Temperature T
STG
.............................................. -65 to 150
°C
NOTE:
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 condi-
tions for extended periods may affect reliability.
RECOMMENDED CONDITIONS
PARAMETER
Cathode Voltage
Cathode Current
SYMBOL
V
KA
I
K
RATING
V
REF
to 20
10
UNIT
V
mA
TYPICAL THERMAL RESISTANCES
PACKAGE
SOT-23
0
JA
0
JC
TYPICAL DERATING
1.7 mW/°C
575°C/W 150°C/W
Typical deratings of the thermal resistances are given for ambient
temperature >25°.
ELECTRICAL CHARACTERISTICS
Electrical characteristics at 25°C I
K
= 10mA V
K
= V
REF
, unless otherwise specified.
PARAMETER
SYMBOL
FIGURE
CONDITIONS
MIN
TYP
SPX2431A
Reference Voltage
∆V
REF
withTemp.*
Ratio of Change in V
REF
to Cathode Voltage
Reference Input Current
I
REF
Temp Deviation
Min I
K
for Regulation
Off State Leakage
Dynamic Output
Impedance
V
REF
TC
∆
V
REF
∆V
K
I
REF
∆I
REF
I
K(MIN)
I
K(OFF)
4
Z
KA
2
2
2
2
3
3
3
2
V
REF
= 0V,
V
KA
= 20V
ƒ
z
≤
1kHz
I
K
= 1 to 100mA
T
J
= 0°C to 105°C
V
REF
to 10V
10V to 20V
-2.7
-2.0
T
J
= 0°C to 105°C
2.487
2.480
2.500
0.07
-1.01
-0.4
0.7
0.4
0.4
0.04
0.15
0.5
2.513
2.520
0.20
0.3
4.0
1.2
1.0
-2.7
-2.0
2.474
2.460
MAX
MIN
TYP
SPX2431
2.500
0.07
-1.01
-0.4
0.7
0.4
0.4
0.04
0.15
2.526
2.540
0.20
0.3
4.0
1.2
1.0
500
0.5
µA
µA
mA
nA
Ω
V
V
mV/°C
mV/V
MAX
UNITS
Date: 1/19/05
SPX2431 Precision Adjustable Shunt Regulator
© Copyright 2005 Sipex Corporation
2
CALCULATING AVERAGE TEMPERATURE COEFFICIENT (TC)
ppm
0
%
0
mV
0
∆V
REF
∆T
-5
•
TC in mV /
°C
=
∆
V
REF
(mV)
∆
T
A
•
TC in % /
°C
=
(
∆
V
REF
∆
V
REF
at 25°C
∆
T
A
)
x 100
5000
0.5
0
15
30
45
60
75
90
105
•
TC in ppm /
°C
=
(
∆
V
REF
∆
V
REF
at 25°C
∆
T
A
)
x 10
6
Junction Temperature (°C)
0.0033mV /°C
0.0027% /
°C
27ppm/°C
Figure 1. V
REF
VS Temperature
TEST CIRCUITS
V
IN
V
KA =
V
REF
V
IN
V
KA
V
IN
V
KA
I
K (OFF)
I
REF
I
K
R1
I
REF
(V
REF
)
R2
I
K
Figure 2. Test Circuit for V
KA
= V
REF
Figure 3. Test Circuit for V
KA
> V
REF
Figure 4. Test Circuit for I
KOFF
Date: 1/19/05
SPX2431 Precision Adjustable Shunt Regulator
© Copyright 2005 Sipex Corporation
3
TYPICAL PERFORMANCE CHARACTERISTICS
150
125
100
V
KA
= V
REF
0°C to 105°C
2.53
2.52
V
KA
= V
REF
I
K
= 10mA
V
REF
Reference Voltage (V)
3
I
K
Cathode Current (mA)
2.51
2.50
2.49
2.48
2.47
2.46
2.45
-60
75
50
25
0
-25
-50
-75
-100
-2
-1
0
1
2
V
KA
Cathode Voltage (V)
-30
0
30
60
90
120
T
A
Ambient Temperature (°C)
Figure 5. High Current Operating Characteristics
Figure 6. Reference Voltage VS Ambient Tempetature
900
3.0
700
I
REF
Reference Input Current (µA)
800
V
KA
= V
REF
0° to 105°C
2.5
2.0
1.5
1.0
0.5
0
-60
R1 = 10kΩ
R2 =
∞
I
K
= 10mA
I
K
Cathode Current (µA)
600
500
400
300
200
100
0
-100
-200
-1.0
1.0
2.0
V
KA
Cathode Voltage (V)
0
3.0
105°C
25°C
-0°C
-30
0
30
60
90
120
T
A
Ambient Temperature (°C)
Figure 7. Low Current Operating Characteristics
Figure 8. Reference Input Current VS Ambient
Temperature
70
60
0
0°C
∆V
REF
(mV)
Noise Voltage n/√Hz
-10
50
40
30
20
10
0
10
V
KA
= V
REF
I
K
= 10mA
T
A
= 25°C
100
1K
10K
100K
-20
25°C
75°C
-30
I
KA
= 10mA
-40
125°C
-50
0
3
6
9
12 15
18
21
24
27 30
V
KA
Cathode Voltage (V)
f Frequency (Hz)
Figure 9. Reference Voltage Line Regulation VS
Cathode Voltage and T
AMBIENT
Figure 10. Noise Voltage VS Frequency
Date: 1/19/05
SPX2431 Precision Adjustable Shunt Regulator
© Copyright 2005 Sipex Corporation
4
TYPICAL PERFORMANCE CHARACTERISTICS: Continued
0.150
REF LEVEL
60.000dB
0.0deg
/DIV
10.000dB
45.000deg
MARKER 25 297 698.000 Hz
MAG (A/R)
-0.025 dB
MARKER 25 297 698.000 Hz
PHASE (A/R)
93.320 deg
215°
180°
PHASE
135°
90°
45°
0°
GAIN
0dB
-10dB
-20dB
-45°
-90°
-135°
-180°
-215°
Z
KA
Dynamic Impedance (Ω)
0.125
0.100
0.075
0.050
0.025
0.0
-60
V
KA
= V
REF
I
K
= 1 to 100mA
f≤1kHz
60dB
50dB
40dB
30dB
20dB
10dB
-30dB
-30
0
30
60
90
120
-40dB
10
100
1K
10K
100K
1M
10M
T
A
Free Air Temperature
START 10.000Hz
STOP 50 000 000.000Hz
Figure 11. Low Frequency Dynamic Output Impedance
VS T
AMBIENT
Figure 12. Small Signal Gain and Phase VS Frequency;
I
K
= 10mA, T
A
= 25°C
V
OUT
V
IN
230Ω
9µF
15kΩ
I
K
V
OUT
V
IN
8.25kΩ
GND
Figure 13. Test Circuit for Gain and Phase Frequency
Response
V
IN
250Ω
Figure 14. Frequency = 100kHz, I
K
= 10mA, T
A
= 25°C
100
90
I
K
Cathode Current (mA)
A: V
KA
= V
REF
B: V
KA
= 5V at I
K
=10mA
C: V
KA
=10V at I
K
=10mA
D: V
KA
=15V at I
K
=10mA
C
V
OUT
I
K
f
p = 100kHz
50Ω
80
70
60
50
40
STABLE
A
STABLE
30
20
10
0
10
0
T
A = 25°C
B
D
GND
10
1
10
2
10
3
10
4
10
5
10
6
10
7
C
L
Load Capacitance (pF)
Figure 15. Test Circuit for Pulse Response
Figure 16. Stability Boundary Conditions
Date: 1/19/05
SPX2431 Precision Adjustable Shunt Regulator
© Copyright 2005 Sipex Corporation
5
