NSC LMS8117ADT-1.8 1a low-dropout linear regulator Datasheet

LMS8117A
1A Low-Dropout Linear Regulator
General Description
Features
The LMS8117A is a series of low dropout voltage regulators
with a dropout of 1.2V at 1A of load current. It has the same
pin-out as National Semiconductor’s industry standard
LM317.
The LMS8117A is available in an adjustable version, which
can set the output voltage from 1.25V to 13.8V with only two
external resistors. In addition, it is also available in two fixed
voltages, 1.8V and 3.3V.
The LMS8117A offers current limiting and thermal shutdown.
Its circuit includes a zener trimmed bandgap reference to
assure output voltage accuracy to within ± 1%.
The LMS8117A series is available in SOT-223 and TO-252
D-PAK packages. A minimum of 10µF tantalum capacitor is
required at the output to improve the transient response and
stability.
n
n
n
n
n
n
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Available in 1.8V, 3.3V, and Adjustable Versions
Space Saving SOT-223 and TO-252 Packages
Current Limiting and Thermal Protection
Output Current
1A
Temperature Range
0˚C to 125˚C
Line Regulation
0.2% (Max)
Load Regulation
0.4% (Max)
Applications
n
n
n
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Post Regulator for Switching DC/DC Converter
High Efficiency Linear Regulators
Battery Charger
Battery Powered Instrumentation
Typical Application
Fixed Output Regulator
10119628
© 2005 National Semiconductor Corporation
DS101196
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LMS8117A 1A Low-Dropout Linear Regulator
April 2005
LMS8117A
Ordering Information
Package
3-lead SOT-223
3-lead TO-252
Temperature Range (TJ)
Packaging Marking
Transport Media
NSC
Drawing
LMS8117AMP-ADJ
LS0A
1k Tape and Reel
MP04A
LMS8117AMPX-ADJ
LS0A
2k Tape and Reel
LMS8117AMP-1.8
LS00
1k Tape and Reel
LMS8117AMPX-1.8
LS00
2k Tape and Reel
LMS8117AMP-3.3
LS01
1k Tape and Reel
LMS8117AMPX-3.3
LS01
2k Tape and Reel
0˚C to +125˚C
LMS8117ADT-ADJ
LMS8117ADT-ADJ
Rails
LMS8117ADTX-ADJ
LMS8117ADT-ADJ
2.5k Tape and Reel
TD03B
LMS8117ADT-1.8
LMS8117ADT-1.8
Rails
LMS8117ADTX-1.8
LMS8117ADT-1.8
2.5k Tape and Reel
LMS8117ADT-3.3
LMS8117ADT-3.3
Rails
LMS8117ADTX-3.3
LMS8117ADT-3.3
2.5k Tape and Reel
Connection Diagrams
SOT-223
TO-252
10119699
Top View
10119638
Top View
Block Diagram
10119601
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2
Soldering Information
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
ESD Tolerance (Note 3)
Infrared (20 sec)
Maximum Input Voltage (VIN to GND)
Operating Ratings (Note 1)
LMS8117A-ADJ, LMS8117A-1.8,
LMS8117A-3.3
Power Dissipation (Note 2)
235˚C
2000V
Input Voltage (VIN to GND)
20V
LMS8117A-ADJ, LMS8117A-1.8,
LMS8117A-3.3
Internally Limited
Junction Temperature (TJ)
(Note 2)
150˚C
Storage Temperature Range
-65˚C to 150˚C
15V
0˚C to 125˚C
Junction Temperature Range
(TJ)(Note 2)
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, 0˚C to 125˚C.
Symbol
VREF
VOUT
∆VOUT
Min
(Note 5)
Typ
(Note 4)
Max
(Note 5)
Units
LMS8117A-ADJ
IOUT = 10mA, VIN-VOUT = 2V, TJ = 25˚C
10mA ≤ IOUT ≤ 1A, 1.4V ≤ VIN-VOUT ≤ 10V
1.238
1.225
1.250
1.250
1.262
1.270
V
V
LMS8117A-1.8
IOUT = 10mA, VIN = 3.8V, TJ = 25˚C
0 ≤ IOUT ≤ 1A, 3.2V ≤ VIN ≤ 10V
1.782
1.746
1.800
1.800
1.818
1.854
V
V
LMS8117A-3.3
IOUT = 10mA, VIN = 5V TJ = 25˚C
0 ≤ IOUT ≤ 1A, 4.75V ≤ VIN ≤ 10V
3.267
3.235
3.300
3.300
3.333
3.365
V
V
0.035
0.2
%
1
6
mV
1
6
mV
Parameter
Reference Voltage
Output Voltage
Line Regulation (Note
6)
Conditions
LMS8117A-ADJ
IOUT = 10mA, 1.5V ≤ VIN-VOUT ≤ 13.75V
LMS8117A-1.8
IOUT = 0mA, 3.2V ≤ VIN ≤ 10V
LMS8117A-3.3
IOUT = 0mA, 4.75V ≤ VIN ≤ 15V
∆VOUT
VIN-V OUT
ILIMIT
Load Regulation (Note LMS8117A-ADJ
6)
VIN-VOUT = 3V, 10mA ≤ IOUT ≤ 1A
Dropout Voltage
(Note 7)
0.2
0.4
%
LMS8117A-1.8
VIN = 3.2V, 0 ≤ IOUT ≤ 1A
1
10
mV
LMS8117A-3.3
VIN = 4.75V, 0 ≤ IOUT ≤ 1A
1
10
mV
IOUT = 100mA
1.1
1.15
V
IOUT = 500mA
1.15
1.2
V
IOUT = 1A
1.2
1.25
V
1.4
1.9
A
1.7
5
mA
5
10
mA
5
10
mA
0.01
0.1
%/W
Current Limit
VIN-VOUT = 5V, TJ = 25˚C
Minimum Load
Current (Note 8)
LMS8117A-ADJ
VIN = 15V
Quiescent Current
LMS8117A-1.8
VIN ≤ 15V
1.0
LMS8117A-3.3
VIN ≤ 15V
Thermal Regulation
TA = 25˚C, 30ms Pulse
Ripple Regulation
fRIPPLE = 120Hz, VIN-VOUT = 3V
VRIPPLE = 1VPP
Adjust Pin Current
Adjust Pin Current
Change
10mA ≤ IOUT ≤ 1A,
1.4V ≤ VIN-VOUT ≤ 10V
3
60
75
dB
60
120
µA
0.2
5
µA
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LMS8117A
Absolute Maximum Ratings (Note 1)
LMS8117A
Electrical Characteristics
(Continued)
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, 0˚C to 125˚C.
Symbol
Parameter
Conditions
Temperature Stability
Min
(Note 5)
Typ
(Note 4)
Max
(Note 5)
Units
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
3-Lead SOT-223
3-Lead TO-252
15.0
10
˚C/W
˚C/W
Thermal Resistance
Junction-to-Ambient
(No heat sink;
No air flow)
3-Lead SOT-223
3-Lead TO-252 (Note 9)
136
92
˚C/W
˚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.
Note 4: Typical Values represent the most likely parametric norm.
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: The minimum output current required to maintain regulation.
Note 9: Minimum pad size of 0.038in2
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LMS8117A
Typical Performance Characteristics
Dropout Voltage (VIN-V
OUT)
Short-Circuit Current
10119623
10119622
Load Regulation
LMS8117A-ADJ Ripple Rejection vs. Current
10119606
10119624
LMS8117A-ADJ Ripple Rejection
Temperature Stability
10119607
10119625
5
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LMS8117A
Typical Performance Characteristics
(Continued)
Adjust Pin Current
LMS8117A-1.8 Load Transient Response
10119626
10119608
LMS8117A-3.3 Load Transient Response
LMS8117A-1.8 Line Transient Response
10119610
10119609
LMS8117A-3.3 Line Transient Response
10119611
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LMS8117A
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 Adjust Terminal Bypass Capacitor
The adjust terminal can be bypassed to ground with a bypass capacitor (CADJ) to improve ripple rejection. This bypass capacitor prevents ripple from being amplified as the
output voltage is increased. At any ripple frequency, the
impedance of the CADJ should be less than R1 to prevent the
ripple from being amplified:
1/(2π*fRIPPLE*CADJ) < R1
The R1 is the resistor between the output and the adjust pin.
Its value is normally in the range of 100-200Ω. For example,
with R1 = 124Ω and fRIPPLE = 120Hz, the CADJ should be >
11µF.
10119617
FIGURE 1. Basic Adjustable Regulator
1.3 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 LMS8117A 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 be greater than 0.5Ω and less than 5Ω. In
the case of the adjustable regulator, when the CADJ is used,
a larger output capacitance (22µf tantalum) is required.
3.0 LOAD REGULATION
The LMS8117A regulates the voltage that appears between
its output and ground pins, or between its output and adjust
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 2, 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.
2.0 OUTPUT VOLTAGE
The LMS8117A adjustable version develops a 1.25V reference voltage, VREF, between the output and the adjust terminal. As shown in Figure 1 , this voltage is applied across
resistor R1 to generate a constant current I1. The current
IADJ from the adjust terminal could introduce error to the
output. But since it is very small (60µA) compared with the I1
and very constant with line and load changes, the error can
be ignored. The constant current I1 then flows through the
output set resistor R2 and sets the output voltage to the
desired level.
For fixed voltage devices, R1 and R2 are integrated inside
the devices.
For fixed voltage devices, R1 and R2 are integrated inside
the devices.
10119618
FIGURE 2. Typical Application using Fixed Output
Regulator
7
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LMS8117A
Application Note
(Continued)
When the adjustable regulator is used (Figure 3), the best
performance is obtained with the positive side of the resistor
R1 tied directly to the output terminal of the regulator rather
than near the load. This eliminates line drops from appearing
effectively in series with the reference and degrading regulation. For example, a 5V regulator with 0.05Ω resistance
between the regulator and load will have a load regulation
due to line resistance of 0.05Ω x IL. If R1 (=125Ω) is connected near the load, the effective line resistance will be
0.05Ω (1+R2/R1) or in this case, it is 4 times worse. In
addition, the ground side of the resistor R2 can be returned
near the ground of the load to provide remote ground sensing and improve load regulation.
10119615
FIGURE 4. Regulator with Protection Diode
5.0 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 5. 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.
10119619
FIGURE 3. Best Load Regulation using Adjustable
Output Regulator
4.0 PROTECTION DIODES
Under normal operation, the LMS8117A regulators do not
need any protection diode. With the adjustable device, the
internal resistance between the adjust and output terminals
limits the current. No diode is needed to divert the current
around the regulator even with capacitor on the adjust terminal. The adjust pin can take a transient signal of ± 25V with
respect to the output voltage without damaging the device.
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 LMS8117A
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 4.
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RθJC(Component
Variables)
RθCA (Application
Variables)
Leadframe Size & Material Mounting Pad Size,
Material, & Location
No. of Conduction Pins
Placement of Mounting
Pad
Die Size
PCB Size & Material
Die Attach Material
Traces Length & Width
Molding Compound Size
and Material
Adjacent Heat Sources
Volume of Air
Ambient Temperatue
Shape of Mounting Pad
8
LMS8117A
Application Note
(Continued)
10119637
FIGURE 5. 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
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
The LMS8117A regulators have internal thermal shutdown to
protect the device from over-heating. Under all possible
operating conditions, the junction temperature of the
LMS8117A must be within the range of 0˚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 6 shows the voltages and currents which are present
in the circuit.
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 7 and Figure
8 reflects the same test results as what are in the Table 1.
Figure 9 and Figure 10 shows the maximum allowable power
dissipation vs. ambient temperature for the SOT-223 and
TO-252 device. Figure 11 and Figure 12 shows the maximum allowable power dissipation vs. copper area (in2) for
the SOT-223 and TO-252 devices. Please see AN–1028 for
power enhancement techniques to be used with SOT-223
and TO-252 packages.
10119616
FIGURE 6. Power Dissipation Diagram
The next parameter which must be calculated is the maximum allowable temperature rise, TR(max):
9
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LMS8117A
Application Note
(Continued)
TABLE 1. θJA Different Heatsink Area
Layout
Copper Area
Thermal Resistance
Top Side (in2)*
Bottom Side (in2)
(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
47
6
1
0
66
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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LMS8117A
Application Note
(Continued)
10119636
FIGURE 10. Maximum Allowable Power Dissipation vs.
Ambient Temperature for TO-252
10119613
FIGURE 7. θJA vs. 1oz Copper Area for SOT-223
10119614
10119634
FIGURE 8. θJA vs. 2oz Copper Area for TO-252
FIGURE 11. Maximum Allowable Power Dissipation vs.
1oz Copper Area for SOT-223
10119635
10119612
FIGURE 12. Maximum Allowable Power Dissipation vs.
2oz Copper Area for TO-252
FIGURE 9. Maximum Allowable Power Dissipation vs.
Ambient Temperature for SOT-223
11
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LMS8117A
Application Note
(Continued)
10119620
FIGURE 13. Top View of the Thermal Test Pattern in Actual Scale
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LMS8117A
Application Note
(Continued)
10119621
FIGURE 14. Bottom View of the Thermal Test Pattern in Actual Scale
13
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LMS8117A
Typical Application Circuits
10119629
1.25V to 10V Adjustable Regulator with Improved Ripple Rejection
10119627
5V Logic Regulator with Electronic Shutdown*
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14
LMS8117A
Physical Dimensions
inches (millimeters) unless otherwise noted
3-Lead SOT-223
NS Package Number MP04A
15
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LMS8117A 1A Low-Dropout Linear Regulator
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
3-Lead TO-252
NS Package Number TD03B
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