LM2937ET-5.0 National Semiconductor, LM2937ET-5.0 Datasheet - Page 10

• Manufacturer Part Number: LM2937ET-5.0
• Description: IC, LDO VOLT REG, 5V, 0.5A, TO-220
• Manufacturer: National Semiconductor

Specifications of LM2937ET-5.0

• Primary Input Voltage: 26V
• Output Voltage Fixed: 5V
• Dropout Voltage Vdo: 500mV
• No. Of Pins: 3
• Output Current: 500mA
• Operating Temperature Range: -40°C To +125°C
• Termination Type: Through Hole
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

www.national.com
Application Hints
When a value for θ
a heatsink must be selected that has a value that is less than
or equal to this number.
θ
in the catalog, or shown in a curve that plots temperature rise
vs power dissipation for the heatsink.
HEATSINKING TO-263 AND SOT-223 PACKAGE PARTS
Both the TO-263 (“S”) and SOT-223 (“MP”) packages use a
copper plane on the PCB and the PCB itself as a heatsink.
To optimize the heat sinking ability of the plane and PCB,
solder the tab of the package to the plane.
Figure 3 shows for the TO-263 the measured values of θ
for different copper area sizes using a typical PCB with 1
ounce copper and no solder mask over the copper area used
for heatsinking.
As shown in the figure, increasing the copper area beyond 1
square inch produces very little improvement. It should also
be observed that the minimum value of θ
package mounted to a PCB is 32˚C/W.
As a design aid, Figure 4 shows the maximum allowable
power dissipation compared to ambient temperature for the
TO-263 device (assuming θ
mum junction temperature is 125˚C).
(H−A)
FIGURE 3. θ
is specified numerically by the heatsink manufacturer
(J−A)
(H−A)
vs. Copper (1 ounce) Area for the
TO-263 Package
is found using the equation shown,
(J−A)
(Continued)
is 35˚C/W and the maxi-
(J−A)
01128028
for the TO-263
(J−A)
10
Figure 5 and Figure 6 show the information for the SOT-223
package. Figure 6 assumes a θ
copper and 51˚C/W for 2 ounce copper and a maximum
junction temperature of +85˚C.
FIGURE 4. Maximum Power Dissipation vs. T
FIGURE 5. θ
(J−A)
the TO-263 Package
SOT-223 Package
vs Copper (2 ounce) Area for the
(J−A)
of 74˚C/W for 1 ounce
01128030
01128029
AMB
for