LM2937ES-3.3/NOPB National Semiconductor, LM2937ES-3.3/NOPB Datasheet - Page 9
Manufacturer Part Number
IC REGULATOR LDO TO-263
Specifications of LM2937ES-3.3/NOPB
Voltage - Output
Voltage - Input
Up to 26V
Voltage - Dropout (typical)
0.11V @ 50mA
Number Of Regulators
Current - Output
-40°C ~ 125°C
Package / Case
TO-263-3, D²Pak (3 leads + Tab), TO-263AA
Number Of Outputs
Input Voltage Max
Voltage Regulation Accuracy
+/- 5 %
Maximum Operating Temperature
+ 125 C
Minimum Operating Temperature
- 40 C
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Current - Limit (min)
Lead Free Status / Rohs Status
When a value for θ
a heatsink must be selected that has a value that is less than
or equal to this number.
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
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).
FIGURE 4. Maximum Power Dissipation vs T
FIGURE 3. θ
is specified numerically by the heatsink manufacturer
the TO-263 Package
vs Copper (1 ounce) Area for the
is found using the equation shown,
is 35˚C/W and the maxi-
for the TO-263
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.
Please see AN1028 for power enhancement techniques to
be used with the SOT-223 package.
SOT-223 SOLDERING RECOMMENDATIONS
It is not recommended to use hand soldering or wave sol-
dering to attach the small SOT-223 package to a printed
circuit board. The excessive temperatures involved may
cause package cracking.
Either vapor phase or infrared reflow techniques are pre-
ferred soldering attachment methods for the SOT-223 pack-
FIGURE 6. Maximum Power Dissipation vs T
FIGURE 5. θ
the SOT-223 Package
vs Copper (2 ounce) Area for the
of 74˚C/W for 1 ounce