TI SM74503

SM74503
SM74503 800mA Low-Dropout Linear Regulator
Literature Number: SNVS722
SM74503
800mA Low-Dropout Linear Regulator
General Description
Features
The SM74503 is a series of low dropout voltage regulators
with a dropout of 1.2V at 800mA of load current. It has the
same pin-out as National Semiconductor's industry standard
LM317.
The SM74503 is available in two fixed voltages, 3.3V and 5V.
The SM74503 offers current limiting and thermal shutdown.
Its circuit includes a zener trimmed bandgap reference to assure output voltage accuracy to within ±1%.
The SM74503 series is available in SOT-223 and TO-252 DPAK packages. A minimum of 10µF tantalum capacitor is
required at the output to improve the transient response and
stability.
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Renewable Energy Grade
Available in 3.3V and 5V Versions
Space Saving SOT-223 Package
Current Limiting and Thermal Protection
Output Current
800mA
Line Regulation
0.2% (Max)
Load Regulation
0.4% (Max)
Temperature Range
−40°C to 125°C
Applications
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Photovoltaic Electronics
Post Regulator for Switching DC/DC Converter
High Efficiency Linear Regulators
Battery Charger
Battery Powered Instrumentation
Typical Application
Fixed Output Regulator
30160628
© 2011 Texas Instruments Incorporated
301606
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SM74503 800mA Low-Dropout Linear Regulator
November 30, 2011
SM74503
Ordering Information
Package
4-lead SOT-223
3-lead TO-252
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Part Number
Packaging Marking
Transport Media
SM74503MP-3.3
S503
1000 UnitsTape and Reel
SM74503MPE-3.3
S503
250 UnitsTape and Reel
SM74503MPX-3.3
S503
2000 UnitsTape and Reel
SM74503MP-5.0
S503
1000 UnitsTape and Reel
SM74503MPE-5.0
S503
250 UnitsTape and Reel
SM74503MPX-5.0
S503
2000 UnitsTape and Reel
SM74503TD-3.3
S74503-3.3
75 Unit Raill
SM74503TDE-3.3
S74503-3.3
250 UnitsTape and Reel
SM74503TDX-3.3
S74503-3.3
2500 UnitsTape and Reel
SM74503TD-5.0
S74503-5.0
75 Unit Rail
SM74503TDE-5.0
S74503-5.0
250 UnitsTape and Reel
SM74503TDX-5.0
S74503-5.0
2500 UnitsTape and Reel
2
NSC Drawing
MP04A
TD03B
SM74503
Block Diagram
30160601
TO-252
Connection Diagrams
SOT-223
30160638
Top View
30160604
Top View
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SM74503
Lead Temperature
SOT-223 (MP) Package
ESD Tolerance (Note 3)
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the Texas Instruments Sales Office/
Distributors for availability and specifications.
Maximum Input Voltage (VIN to GND)
Power Dissipation (Note 2)
Junction Temperature (TJ)
(Note 2)
Storage Temperature Range
260°C, 4 sec
2000V
Operating Ratings
20V
Internally Limited
(Note 1)
Input Voltage (VIN to GND)
15V
Junction Temperature Range (TJ)(Note 2)
SM74503
−40°C to 125°C
150°C
-65°C to 150°C
SM74503 Electrical Characteristics
Typicals and limits appearing in normal type apply for TJ = 25°C. Limits appearing in Boldface type apply over the entire junction
temperature range for operation, −40°C to 125°C.
Symbol
VOUT
Min
(Note 5)
Typ
(Note 4)
Max
(Note 5)
Units
SM74503-3.3
IOUT = 10mA, VIN = 5V, TJ = 25°C
3.267
3.168
3.300
3.300
3.333
3.432
V
V
SM74503-5.0
IOUT = 10mA, VIN = 7V, TJ = 25°C
4.950
4.800
5.000
5.000
5.050
5.200
V
V
1
10
mV
1
15
mV
1
15
mV
1
20
mV
IOUT = 100mA
1.10
1.30
V
IOUT = 500mA
1.15
1.35
V
IOUT = 800mA
1.20
1.40
V
1200
1500
mA
5
15
mA
5
15
mA
0.01
0.1
%/W
Parameter
Output Voltage
Conditions
0 ≤ IOUT ≤ 800mA, 4.75V ≤ VIN ≤ 10V
0 ≤ IOUT ≤ 800mA, 6.5V ≤ VIN ≤ 12V
ΔVOUT
Line Regulation
(Note 6)
SM74503-3.3
IOUT = 0mA, 4.75V ≤ VIN ≤ 15V
SM74503-5.0
IOUT = 0mA, 6.5V ≤ VIN ≤ 15V
ΔVOUT
Load Regulation
(Note 6)
SM74503-3.3
VIN = 4.75V, 0 ≤ IOUT ≤ 800mA
SM74503-5.0
VIN = 6.5V, 0 ≤ IOUT ≤ 800mA
VIN-V OUT
ILIMIT
Dropout Voltage
(Note 7)
Current Limit
VIN-VOUT = 5V, TJ = 25°C
Quiescent Current
SM74503-3.3
800
VIN ≤ 15V
SM74503-5.0
VIN ≤ 15V
Thermal Regulation
TA = 25°C, 30ms Pulse
Ripple Regulation
fRIPPLE =1 20Hz, VIN-VOUT = 3V VRIPPLE =
1VPP
Temperature Stability
60
75
dB
0.5
%
0.3
%
%
Long Term Stability
TA = 125°C, 1000Hrs
RMS Output Noise
(% of VOUT), 10Hz ≤ f ≤10kHz
0.003
Thermal Resistance
Junction-to-Case
4-Lead SOT-223
15.0
°C/W
3-Lead TO-252
10
°C/W
Thermal Resistance
Junction-to-Ambient
No air flow)
4-Lead SOT-223 (No heat sink)
136
°C/W
3-Lead TO-252 (No heat sink)(Note 8)
92
°C/W
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see the Electrical Characteristics.
Note 2: The maximum power dissipation is a function of TJ(max) , θJA, and TA. The maximum allowable power dissipation at any ambient temperature is
PD = (TJ(max)–TA)/θJA. All numbers apply for packages soldered directly into a PC board.
Note 3: For testing purposes, ESD was applied using human body model, 1.5kΩ in series with 100pF.
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4
Note 5: All limits are guaranteed by testing or statistical analysis.
Note 6: Load and line regulation are measured at constant junction room temperature.
Note 7: The dropout voltage is the input/output differential at which the circuit ceases to regulate against further reduction in input voltage. It is measured when
the output voltage has dropped 100mV from the nominal value obtained at VIN = VOUT +1.5V.
Note 8: Minimum pad size of 0.038in2
Typical Performance Characteristics
Dropout Voltage (VIN-V OUT)
Short-Circuit Current
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30160622
Load Regulation
Temperature Stability
30160643
30160625
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SM74503
Note 4: Typical Values represent the most likely parametric norm.
SM74503
SM74503-5.0 Load Transient Response
SM74503-5.0 Line Transient Response
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SM74503
Application Note
1.0 EXTERNAL CAPACITORS/STABILITY
1.1 Input Bypass Capacitor
An input capacitor is recommended. A 10µF tantalum on the
input is a suitable input bypassing for almost all applications.
1.2 Output Capacitor
The output capacitor is critical in maintaining regulator stability, and must meet the required conditions for both minimum
amount of capacitance and ESR (Equivalent Series Resistance). The minimum output capacitance required by the
SM74503 is 10µF, if a tantalum capacitor is used. Any increase of the output capacitance will merely improve the loop
stability and transient response. The ESR of the output capacitor should range between 0.3Ω - 22Ω.
30160615
FIGURE 2. Regulator with Protection Diode
2.0 LOAD REGULATION
The SM74503 regulates the voltage that appears between its
output and ground pins. In some cases, line resistances can
introduce errors to the voltage across the load. To obtain the
best load regulation, a few precautions are needed.
Figure 1, shows a typical application using a fixed output regulator. The Rt1 and Rt2 are the line resistances. It is obvious
that the VLOAD is less than the VOUT by the sum of the voltage
drops along the line resistances. In this case, the load regulation seen at the RLOAD would be degraded from the data
sheet specification. To improve this, the load should be tied
directly to the output terminal on the positive side and directly
tied to the ground terminal on the negative side.
4.0 HEATSINK REQUIREMENTS
When an integrated circuit operates with an appreciable current, its junction temperature is elevated. It is important to
quantify its thermal limits in order to achieve acceptable performance and reliability. This limit is determined by summing
the individual parts consisting of a series of temperature rises
from the semiconductor junction to the operating environment. A one-dimensional steady-state model of conduction
heat transfer is demonstrated in Figure 3. The heat generated
at the device junction flows through the die to the die attach
pad, through the lead frame to the surrounding case material,
to the printed circuit board, and eventually to the ambient environment. Below is a list of variables that may affect the
thermal resistance and in turn the need for a heatsink.
RθJC (Component
Variables)
Leadframe Size & Material
No. of Conduction Pins
Die Size
Die Attach Material
Molding Compound Size
and Material
30160618
FIGURE 1. Typical Application using Fixed Output
Regulator
Rθ CA (Application
Variables)
Mounting Pad Size,
Material, & Location
Placement of Mounting Pad
PCB Size & Material
Traces Length & Width
Adjacent Heat Sources
Volume of Air
Ambient Temperatue
Shape of Mounting Pad
3.0 PROTECTION DIODES
Under normal operation, the SM74503 regulators do not need
any protection diode. When a output capacitor is connected
to a regulator and the input is shorted to ground, the output
capacitor will discharge into the output of the regulator. The
discharge current depends on the value of the capacitor, the
output voltage of the regulator, and rate of decrease of VIN. In
the SM74503 regulators, the internal diode between the output and input pins can withstand microsecond surge currents
of 10A to 20A. With an extremely large output capacitor
(≥1000 µF), and with input instantaneously shorted to ground,
the regulator could be damaged.
In this case, an external diode is recommended between the
output and input pins to protect the regulator, as shown in
Figure 2.
30160637
FIGURE 3. Cross-sectional view of Integrated Circuit
Mounted on a printed circuit board. Note that the case
temperature is measured at the point where the leads
contact with the mounting pad surface
The SM74503 regulators have internal thermal shutdown to
protect the device from over-heating. Under all possible operating conditions, the junction temperature of the SM74503
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SM74503
must be within the range of –40°C to 125°C. A heatsink may
be required depending on the maximum power dissipation
and maximum ambient temperature of the application. To determine if a heatsink is needed, the power dissipated by the
regulator, PD , must be calculated:
IIN = IL + IG
PD = (VIN-VOUT)I L + VINIG
Figure 4 shows the voltages and currents which are present
in the circuit.
TR(max) = TJ(max)-TA(max)
where TJ(max) is the maximum allowable junction temperature (125°C), and TA(max) is the maximum ambient temperature which will be encountered in the application.
Using the calculated values for TR(max) and PD, the maximum allowable value for the junction-to-ambient thermal resistance (θJA) can be calculated:
θJA = TR(max)/PD
If the maximum allowable value for θJA is found to be ≥136°
C/W for SOT-223 package or ≥92°C/W for TO-252 package,
no heatsink is needed since the package alone will dissipate
enough heat to satisfy these requirements. If the calculated
value for θJA falls below these limits, a heatsink is required.
As a design aid, Table 1 shows the value of the θJA of
SOT-223 and TO-252 for different heatsink area. The copper
patterns that we used to measure these θJAs are shown at the
end of the Application Notes Section. Figure 5 and Figure 6
reflects the same test results as what are in the Table 1
Figure 7 and Figure 8 shows the maximum allowable power
dissipation vs. ambient temperature for the SOT-223 and
TO-252 device. Figure 9 and Figure 10 shows the maximum
allowable power dissipation vs. copper area (in2) for the
SOT-223 and TO-252 devices. Please see AN1028 for power
enhancement techniques to be used with SOT-223 and
TO-252 packages.
30160616
FIGURE 4. Power Dissipation Diagram
The next parameter which must be calculated is the maximum
allowable temperature rise, TR(max):
TABLE 1. θJA Different Heatsink Area
Layout
Copper Area
Top Side
(in2)*
Thermal Resistance
Bottom Side
(θJA,°C/W) SOT-223
(θJA,°C/W) TO-252
1
0.0123
0
136
103
2
0.066
0
123
87
3
0.3
0
84
60
4
0.53
0
75
54
5
0.76
0
69
52
6
1
0
66
47
7
0
0.2
115
84
8
0
0.4
98
70
9
0
0.6
89
63
10
0
0.8
82
57
11
0
1
79
57
12
0.066
0.066
125
89
13
0.175
0.175
93
72
14
0.284
0.284
83
61
15
0.392
0.392
75
55
16
0.5
0.5
70
53
*Tab of device attached to topside copper
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(in2)
8
SM74503
30160636
30160613
FIGURE 8. Maximum Allowable Power Dissipation vs.
Ambient Temperature for TO-252
FIGURE 5. θJA vs. 1oz Copper Area for SOT-223
30160634
30160614
FIGURE 6. θJA vs. 2oz Copper Area for TO-252
FIGURE 9. Maximum Allowable Power Dissipation vs. 1oz
Copper Area for SOT-223
30160612
30160635
FIGURE 7. Maximum Allowable Power Dissipation vs.
Ambient Temperature for SOT-223
FIGURE 10. Maximum Allowable Power Dissipation vs.
2oz Copper Area for TO-252
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SM74503
30160641
FIGURE 11. Top View of the Thermal Test Pattern in Actual Scale
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SM74503
30160642
FIGURE 12. Bottom View of the Thermal Test Pattern in Actual Scale
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SM74503
Typical Application Circuits
30160631
Regulator with Reference
30160630
Adjusting Output of Fixed Regulators
30160632
Battery Backed-Up Regulated Supply
30160633
Low Dropout Negative Supply
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SM74503
Physical Dimensions inches (millimeters) unless otherwise noted
4-Lead SOT-223
NS Package Number MP04A
3-Lead TO-252
NS Package Number TD03B
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SM74503 800mA Low-Dropout Linear Regulator
Notes
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