1
Date: 5/25/04 SPX3940 1A Low Dropout Voltage Regulator © Copyright 2004 Sipex Corporation
1A Low Dropout Voltage Regulator
Fixed Output, Fast Response
SPX3940
DESCRIPTION
FEATURES
■1% Output Accuracy SPX3940A
■Guaranteed 1.5A Peak Current
■Low Quiescent Current
■Low Dropout Voltage of 280mV at 1A
■Extremely Tight Load and Line Regulation
■Extremely Fast Transient Response
■Reverse-battery Protection
■Internal Thermal Protection
■Internal Short Circuit Current Limit
■Replacement for LM3940
■Standard SOT-223, TO-220
and TO-263 packages
®
The SPX3940 is a 1A, accurate voltage regulators with a low drop out voltage of 280mV(typical)
at 1A. These regulators are specifically designed for low voltage applications that require a low
dropout voltage and a fast transient response. They are fully fault protected against over-current,
reverse battery, and positive and negative voltage transients.
The SPX3940 is offered in 3-pin SOT-223, TO-220 & TO-263 packages. For a 3A version, refer
to the SPX29300 data sheet.
APPLICATIONS
■Powering VGA & Sound Card
■Automotive Electronics
■LCD Monitors
■Cordless Telephones
■Power PCTM Supplies
SPX3940
V
OUT
V
IN
+
6.8µF+10µF
1
2
3
Figure 1. Fixed Output Linear Regulator.
TYPICAL APPLICATIONS CIRCUIT
■SMPS Post-Regulator
■Laptop, Palmtop, and Note-
book Computer
■High Efficiency Linear Power
Supplies
■Portable Instrumentation
■Constant Current Regulators
123
SPX3940
3 Pin TO-263
GND
V
IN
V
OUT
Now Available in Lead Free Packaging
2
Date: 5/25/04 SPX3940 1A Low Dropout Voltage Regulator © Copyright 2004 Sipex Corporation
ABSOLUTE MAXIMUM RATINGS
Lead Temperature (soldering, 5 seconds) ................................. 260°C
Storage Temperature Range ..................................... -65°C to +150°C
Operating Junction Temperature Range ................... -40°C to +125°C
Input Voltage (Note 5) ................................................................... 16V
NOTES:
Note 1: Dropout voltage is defined as the input to output differential when the output voltage drops to 99% of its normal value.
Note 2: VIN=VOUT (NOMINAL) + 1V. For example, use VIN=4.3V for a 3.3V regulator. Employ pulse-testing procedures to minimize temperature rise.
Note 3: Ground pin current is the regulator quiescent current. The total current drawn from the source is the sum of the load current to the ground current.
Note 4: Thermal regulation is defined as the change in the output voltage at a time T after a change in power dissipation is applied, excluding load or line regulation effects.
Note 5: Maximum positive supply voltage of 20V must be of limited duration (<100ms) and duty cycle (<1%). The maximum continuous supply voltage is 16V.
At VIN=VOUT + 1V and IOUT = 10 mA, CIN = 6.8 µF, COUT = 10µF; TA= 25°C, unless otherwise specified.
The Boldface applies over the junction temperature range. Adjustable versions are set at 5.0V.
PARAMETER CONDITIONS TYP MIN MAX MIN MAX UNITS
SPX3940A (1%) SP3940 (2%)
1.8V Version
Output Voltage I
OUT
= 10mA 1.8 1.782 1.818 1.764 1.836 V
10mA≤I
OUT
≤1A, 6V≤V
IN
≤16V 1.8 1.755 1.845 1.737 1.863
2.5V Version
Output Voltage I
OUT
= 10mA 2.5 2.475 2.525 2.450 2.550 V
10mA≤I
OUT
≤1A, 6V≤V
IN
≤16V 2.5 2.437 2.563 2.412 2.588
3.3V Version
Output Voltage I
OUT
= 10mA 3.3 3.267 3.333 3.234 3.366 V
10mA≤I
OUT
≤1A, 6V≤V
IN
≤16V 3.3 3.217 3.383 3.184 3.416
5.0V Version
Output Voltage I
OUT
= 10mA 5.0 4.950 5.050 4.900 5.100 V
10mA≤I
OUT
≤1A, 6V≤V
IN
≤16V 5.0 4.875 5.125 4.825 5.175
All Voltage Options
Line Regulation I
O
=10mA, (V
OUT
+1V)≤V
IN
≤16V 0.2 1.0 1.0 %
Load Regulation V
IN
=V
OUT
+1V, 10mA≤I
OUT
≤1A 0.3 1.5 1.5 %
∆VOutput Voltage 20 100 100 ppm/°C
∆TTemperature Coef.
Dropout Voltage (Note 1) I
O
=100mA 70 200 200 mV
(except 1.8V version) I
O
=1A 280 550 550
Ground Current (Note 3) I
O
=750mA, V
IN
=V
OUT
, + 1V 12 25 25 mA
I
O
=1A 18
I
GNDDO
Ground Pin V
IN
=0.1V less than specified V
OUT
1.2 mA
Current at Dropout I
OUT
= 10mA
Current Limit V
OUT
=0V (Note 2) 2.2 1.5 1.5 A
Output Noise Voltage C
L
= 10µF400 µV
RMS
(10Hz to 100kHz)
I
L
=100mA C
L
=33µF260
Thermal Resistance TO-220 Junction to Case, at Tab 3 °C/W
TO-220 Junction to Ambient 60
TO-263 Junction to Case, at Tab 3 °C/W
TO-263 Junction to Ambient 60
SOT-223 Junction to Case, at Tab 15 °C/W
SOT-223 Junction to Ambient 150
ELECTRICAL CHARACTERISTICS
3
Date: 5/25/04 SPX3940 1A Low Dropout Voltage Regulator © Copyright 2004 Sipex Corporation
TYPICAL PERFORMANCE CHARACTERISTICS
Figure 2. Line Regulation Figure 3. Load Regulation
Figure 4. Ground Current vs Load Current Figure 5. Ground Current vs Input Voltage
Reference
Thermal
Shutdown
IN OUT
GND
O.V
I
LIMIT
28V R1
R2
1.240V
+
-
Ibias
BLOCK DIAGRAM
3.310
3.305
3.300
3.295
3.290
3.285
3.280
3.3V Device
IL=4.3mA
CL=10µF
0 0.25 0.5 0.75 1 1.25 1.5
IL (A)
VOUT (V)
V
OUT
(V)
3.320
3.315
3.310
3.305
3.300
3.295
3.290
3.285
3.280
V
IN
(V)
46810121416
3.3V Device
IL = 10mA
CL = 10µF
80.0
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0 00.250.5 0.75 1 1.25 1.5
I
GND
(mA)
IL (A)
3.3V Device
VIN = 4.3V
CL = 10µF
100
95
90
85
80
75
70
-40 -20 0 20 40 60 80 100 120
I
GND
(µA)
V
IN
(V)
3.3V Device
IL = 10 mA
CL = 10µF
4
Date: 5/25/04 SPX3940 1A Low Dropout Voltage Regulator © Copyright 2004 Sipex Corporation
Figure 6. Ground Current vs Load Current in Dropout Figure 7. Dropout Voltage vs Load Current
Figure 8. Ground Current vs Temperature at Figure 9. Output Voltage vs Temperature at
ILOAD = 10mA ILOAD=10mA
100
90
80
70
60
50
40
30
20
10
0
3.3 Device
VIN = 3.2V
CL = 10µF
0 0.25 0.5 0.75 1 1.25 1.5
IL(A)
IGND (mA)
280
270
260
250
240
230
220
210
200
190
180
-40 -20 0 20 40 60 80 100 120
I
GND
(µA)
Temperature (°C)
3.3V Device
V
IN
= 4.3V
IL = 10mA
CL = 10µF
3.320
3.310
3.300
3.290
3.280
3.270
3.260
3.250
3.240
3.230
3.220
-40 -20 0 20 40 60 80 100 120
VOUT(V)
Temperature (°C)
3.3V Device
VIN = 4.3V
IL = 10mA
CL = 10µF
Figure 10. Ground Current vs Temperature at Figure 11. Ground Current vs Temperature in Dropout
ILOAD=500mA at ILOAD=750mA
600
500
400
300
200
100
0
00.250.5 0.75 1 1.25 1.5
V Dropout (mV)
IL (A)
3.3V Device
CL = 10µF
7.00
6.80
6.60
6.40
6.20
6.00
5.80
5.60
5.40
5.20
5.00
-40 -20 0 20 40 60 80 100 120
IGND (mA)
Temperature (°C)
3.3V Device
VIN = 4.3V
IL = 500mA
CL = 10µF
30
29
28
27
26
25
24
23
22
21
20
-40 -20 0 20 40 60 80 100 120
IGND (mA)
Temperature (°C)
3.3V Device
VIN = 3.2V
IL = 750mA
CL = 10µF
TYPICAL PERFORMANCE CHARACTERISTICS
5
Date: 5/25/04 SPX3940 1A Low Dropout Voltage Regulator © Copyright 2004 Sipex Corporation
52.0
50.0
48.0
46.0
44.0
42.0
40.0
38.0
36.0
-40 -20 0 20 40 60 80 100 120
I
GND
(mA)
Temperature (°C)
3.3V Device
V
IN
= 4.3V
IL=1.5A
CL = 10µF
Figure 12. Ground Current vs Temperature at ILOAD= 1.5A Figure 13. Ground Current vs Temperature in Dropout
at ILOAD=1.5A
100
95
90
85
80
75
70
-40 -20 0 20 40 60 80 100 120
I
GND
mA)
Temperature (°C)
3.3V Device
V
IN
= 3.2V
IL = 1.5A
CL = 10µF
350
330
310
290
270
250
230
210
190
170
150
-40 -20 0 20 40 60 80
Temperature (°C)
VDROPOUT (mV)
120100
3.3V Device
IL = 750mA
CL = 10µF
Figure 14. Dropout Voltage vs Temperature at
ILOAD= 750mA
Figure 15. Dropout Voltage vs Temperature at
ILOAD= 1.5mA
Figure 16. Enable Current vs Temperature for VEN= 16V
2.00
1.90
1.80
1.70
1.60
1.50
1.40
1.30
1.20
1.10
1.00
-40 -20 0 20 40 60 80
Temperature (°C)
VTH (V)
120100
3.3V Device
V
IN
= 3.2V
IL = 750mA
CL = 10µF
Figure 17. Enable Threshold vs Temperature
500
480
460
440
420
400
380
360
340
320
-40 -20 0 20 40 60 80
Temperature (°C)
V
DROPOUT
(mV)
120100
3.3V Device
IL = 1.5A
CL = 10µF
35
30
25
20
15
10
5
0
-40 -20 0 20 40 60 80
Temperature (°C)
I
EN
(µA)
120100
3.3V Device
VIN = 3.2V
IL = 750mA
CL = 10µF
TYPICAL PERFORMANCE CHARACTERISTICS
6
Date: 5/25/04 SPX3940 1A Low Dropout Voltage Regulator © Copyright 2004 Sipex Corporation
APPLICATION INFORMATION
The SPX3940 incorporates protection against
over-current faults, reversed load insertion, over
temperature operation, and positive and nega-
tive transient voltage.
Thermal Considerations
Although the SPX3940 offers limiting circuitry
for overload conditions, it is still necessary to
insure that the maximum junction temperature
is not exceeded in the application. Heat will
flow through the lowest resistance path, the
junction-to-case path. In order to insure the best
thermal flow of the component, proper mount-
ing is required. Consult heatsink manufacturer
for thermal resistance and design of heatsink.
For example, TO-220 design:
Assume that VIN = 10V, VOUT = 5V, IOUT = 1.5A,
TA = 50°C/W, θHA= 1°C/W, θCH = 2°C/W, and
θJC = 3°C/W.
Where TA = ambient temperature
θHA = heatsink to ambient thermal resistance
θCH = case to heatsink thermal resistance
θJC = junction to case thermal resistance
The power calculated under these conditions is:
PD = (VIN - VOUT) * IOUT = 7.5W.
And the junction temperature is calculated as
TJ = TA + PD * (θHA + θCH + θJC) or
TJ = 50 + 7.5 * (1 + 2 + 3) = 95°C
Reliable operation is insured.
Capacitor Requirements
The output capacitor is needed to insure stability and minimize the output noise. The value of the
capacitor varies with the load. However, a minimum value of 10µF aluminum capacitor will guarantee
stability over all load conditions. A tantalum capacitor is recommended if a faster load transient
response is needed.
If the power source has a high AC impedance, a 0.1µF ceramic capacitor between input & ground is
recommended.
Minimum Load Current
To ensure a proper behavior of the regulator under light load, a minimum load of 5mA for SPX3940
is required.
SPX3940
V
OUT
V
IN
+
6.8µF+10µF
1
2
3
Figure 18. Fixed Output Linear Regulator.
7
Date: 5/25/04 SPX3940 1A Low Dropout Voltage Regulator © Copyright 2004 Sipex Corporation
PACKAGE: TO-263
E
D
L1
b2
e
b
.160 - .190
.000 - .010
Dimensions in inches
3-PIN TO-263
JEDEC TO-263
(AA) Variation
.020 - .039
.015 - .029
.070 - .110
-
- -
A
A1
b
c
D
E
E1
L
L1
L2
MIN NOM MAX
e .100 BSC
.066
-
.330 - .380
D1 .270 - -
.380 - .420
.245 -
-
H.575 - .625
.070
L3 .010 BSC
123
c
C2
A
H
SEATING PLANE
L
0º-8º
See View C
E/2
View C
GAUGE PLANE
A1
SEATING
PLANE
c
WITH PLATING
BASE METAL
b
SECTION B-B
BB
3 PIN TO-263
8
Date: 5/25/04 SPX3940 1A Low Dropout Voltage Regulator © Copyright 2004 Sipex Corporation
PACKAGE: 3 PIN TO-220
H1
B
SEATING
PLANE
A1
A
CHAMFER
OPTIONAL
C
A2
A
A
E
øP
Q
D
D1
E2 E/2
L
L1
CCDD
b
c
WITH PLATING
BASE METAL
b
CONTACT AREA
1
e
e1
.140 - .190
.020 - .055
Dimensions in
(mm)
3 PIN TO-220
JEDEC TO-220
(AB) Variation
.080 - .115
.015 .027 .040
.045 - .070
.480 - .507
A
A1
A2
b
b2
D1
D2
.380 - .420
E
MIN NOM MAX
c.014 - .024
D.560 - .650
.330 - .355
E1
.270 -.350
E2 - - .030
e.100 BSC
e1 .200 BSC
H1 .230 - .270
L1 - - .250
L2 - - -
∆P.139 - .161
Q.100 - .135
3 PIN TO-220
9
Date: 5/25/04 SPX3940 1A Low Dropout Voltage Regulator © Copyright 2004 Sipex Corporation
AA2
A1
SIDE VIEW
A
A
Seating Plane
C
c
WITH PLATING
BASE METAL
b
EE1
e
e1
D
b
12
3
L1
L
Gauge Plane
VIEW C
SEE VIEW C
B
B
0.89 - 1.12
0.01 - 0.10
Dimensions in (mm)
3 PIN SOT-23
JEDEC TO-236
(AB) Variation
0.88 0.95 1.02
0.30 - 0.50
0.08 - 0.20
0.40 0.50 0.60
0.54 REF
0º - 8º
A
A1
A2
b
c
D
E
E1
L
L1
Ø
MIN NOM MAX
2.80 2.90 3.04
2.10 - 2.64
1.20 1.30 1.40
e
e1
0.95 BSC
1.90 BSC
SECTION B-B
VIEW A-A
Seating Plane
Ø
3 PIN SOT-23
PACKAGE: 3 PIN SOT-23
10
Date: 5/25/04 SPX3940 1A Low Dropout Voltage Regulator © Copyright 2004 Sipex Corporation
Corporation
ANALOG EXCELLENCE
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.
Sipex Corporation
Headquarters and
Sales Office
233 South Hillview Drive
Milpitas, CA 95035
TEL: (408) 934-7500
FAX: (408) 935-7600
ORDERING INFORMATION
TO-263-3 Package (T)
V
OUT
GNDV
IN
Front View
TAB=GND
123
Front View
TAB=GND
TO-220-3 Package (U)
V
IN
V
OUT
GND
321
132
SOT-223 (M3)
GND
Top View
TAB=GND
V
IN
V
OUT
PART NUMBER ACC. OUTPUT VOLTAGE PACKAGE
SPX3940AU-1.8 1% 1.8V 3 lead TO-220
SPX3940AU-2.5 1% 2.5V 3 lead TO-220
SPX3940AU-3.3 1% 3.3V 3 lead TO-220
SPX3940AU-5.0 1% 5.0V 3 lead TO-220
SPX3940AT-1.8 1% 1.8V 3 lead TO-263
SPX3940AT-1.8/TR 1% 1.8V 3 lead TO-263
SPX3940AT-2.5 1% 2.5V 3 lead TO-263
SPX3940AT-2.5/TR 1% 2.5V 3 lead TO-263
SPX3940AT-3.3 1% 3.3V 3 lead TO-263
SPX3940AT-3.3/TR 1% 3.3V 3 lead TO-263
SPX3940AT-5.0 1% 5.0V 3 lead TO-263
SPX3940AT-5.0/TR 1% 5.0V 3 lead TO-263
SPX3940U-1.8 2% 1.8V 3 lead TO-220
SPX3940U-2.5 2% 2.5V 3 lead TO-220
SPX3940U-3.3 2% 3.3V 3 lead TO-220
SPX3940U-5.0 2% 5.0V 3 lead TO-220
PINOUTS
/TR = Tape and Reel
Pack quantity is 500 for TO-263 and 2,500 for SOT-23.
Available in lead free packaging. To order add "-L" suffix to part number.
Example: SPX3940AT-3.3/TR = standard; SPX3940AT-L-3.3/TR = lead free
11
Date: 5/25/04 SPX3940 1A Low Dropout Voltage Regulator © Copyright 2004 Sipex Corporation
PART NUMBER ACC. OUTPUT VOLTAGE PACKAGE
SPX3940T-1.8 2% 1.8V 3 lead TO-263
SPX3940T-1.8/TR 2% 1.8V 3 lead TO-263
SPX3940T-2.5 2% 2.5V 3 lead TO-263
SPX3940T-2.5/TR 2% 2.5V 3 lead TO-263
SPX3940T-3.3 2% 3.3V 3 lead TO-263
SPX3940T-3.3/TR 2% 3.3V 3 lead TO-263
SPX3940T-5.0 2% 5.0V 3 lead TO-263
SPX3940T-5.0/TR 2% 5.0V 3 lead TO-263
SPX3940AM3-1.8 1% 1.8V 3 lead SOT-223
SPX3940AM3-1.8/TR 1% 1.8V 3 lead SOT-223
SPX3940AM3-2.5 1% 2.5V 3 lead SOT-223
SPX3940AM3-2.5/TR 1% 2.5V 3 lead SOT-223
SPX3940AM3-3.3 1% 3.3V 3 lead SOT-223
SPX3940AM3-3.3/TR 1% 3.3V 3 lead SOT-223
SPX3940AM3-5.0 1% 5.0V 3 lead SOT-223
SPX3940AM3-5.0/TR 1% 5.0V 3 lead SOT-223
SPX3940M3-1.8 2% 1.8V 3 lead SOT-223
SPX3940M3-1.8/TR 2% 1.8V 3 lead SOT-223
SPX3940M3-2.5 2% 2.5V 3 lead SOT-223
SPX3940M3-2.5/TR 2% 2.5V 3 lead SOT-223
SPX3940M3-3.3 2% 3.3V 3 lead SOT-223
SPX3940M3-3.3/TR 2% 3.3V 3 lead SOT-223
SPX3940M3-5.0 2% 5.0V 3 lead SOT-223
SPX3940M3-5.0/TR 2% 5.0V 3 lead SOT-223
Available in lead free packaging. To order add "-L" suffix to part number.
Example: SPX3940AM3-3.3/TR = standard; SPX3940AM3-L-3.3/TR = lead free
/TR = Tape and Reel
Pack quantity is 500 for TO-263 and 2,500 for SOT-23.
ORDERING INFORMATION
Corporation
ANALOG EXCELLENCE
Sipex Corporation
Headquarters and
Sales Office
233 South Hillview Drive
Milpitas, CA 95035
TEL: (408) 934-7500
FAX: (408) 935-7600
