LM1117MP-2.5 National Semiconductor, LM1117MP-2.5 Datasheet - Page 11

• Manufacturer Part Number: LM1117MP-2.5
• Description: Linear Voltage Regulator IC
• Manufacturer: National Semiconductor

Specifications of LM1117MP-2.5

• No. Of Pins: 4
• Output Current: 0.8A
• Mounting Type: Surface Mount
• Voltage Regulator Type: LDO Linear
• Peak Reflow Compatible (260 C): No
• Supply Voltage: 15V
• Current Rating: 800A
• Output Voltage Max: 2.5V
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Application Note
The LM1117 regulators have internal thermal shutdown to
protect the device from over-heating. Under all possible
operating conditions, the junction temperature of the LM1117
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 deter-
mine if a heatsink is needed, the power dissipated by the
regulator, P
Figure 6 shows the voltages and currents which are present
in the circuit.
Mounted on a printed circuit board. Note that the case
temperature is measured at the point where the leads
FIGURE 5. Cross-sectional view of Integrated Circuit
I
P
IN
D
= I
= (V
L
Layout
contact with the mounting pad surface
FIGURE 6. Power Dissipation Diagram
+ I
IN
10
12
13
11
D
-V
1
2
3
4
5
6
7
8
9
G
, must be calculated:
OUT
)I
L
+ V
IN
I
G
Top Side (in
(Continued)
0.0123
0.066
0.066
0.175
0.53
0.76
0.3
1
0
0
0
0
0
2
Copper Area
)*
TABLE 1. θ
10091916
Bottom Side (in
10091937
JA
Different Heatsink Area
0.066
0.175
0.2
0.4
0.6
0.8
0
0
0
0
0
0
1
11
The next parameter which must be calculated is the maxi-
mum allowable temperature rise, T
where T
ture (125˚C), and T
perature which will be encountered in the application.
Using the calculated values for T
mum allowable value for the junction-to-ambient thermal
resistance (θ
If the maximum allowable value for θ
≥136˚C/W for SOT-223 package or ≥79˚C/W for TO-220
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 θ
falls below these limits, a heatsink is required.
As a design aid, Table 1 shows the value of the θ
SOT-223 and TO-252 for different heatsink area. The copper
patterns that we used to measure these θ
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. Figures Figure 11 and Figure 12 shows the
maximum allowable power dissipation vs. copper area (in
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.
*Application Note AN-1187 discusses improved thermal per-
formance and power dissipation for the LLP.
2
)
T
θ
JA
R
(max) = T
= T
J
(max) is the maximum allowable junction tempera-
(θ
R
(max)/P
JA
JA
,˚C/W) SOT-223
J
) can be calculated:
(max)-T
136
123
115
125
84
75
69
66
98
89
82
79
93
D
A
(max) is the maximum ambient tem-
Thermal Resistance
A
(max)
R
(max) and P
R
(max):
(θ
JA
,˚C/W) TO-252
JA
JA
103
is found to be
s are shown at
87
60
54
52
47
84
70
63
57
57
89
72
D
www.national.com
, the maxi-
JA
JA
of
2
)