LM2937ET-3.3/NOPB National Semiconductor, LM2937ET-3.3/NOPB Datasheet - Page 9

• Manufacturer Part Number: LM2937ET-3.3/NOPB
• Description: IC REGULATOR LDO TO220-3
• Manufacturer: National Semiconductor
• Type: Voltage Regulatorr

Specifications of LM2937ET-3.3/NOPB

• Regulator Topology: Positive Fixed
• Voltage - Output: 3.3V
• Voltage - Input: Up to 26V
• Voltage - Dropout (typical): 0.11V @ 50mA
• Number Of Regulators: 1
• Current - Output: 500mA
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Through Hole
• Package / Case: TO-220-3 (Straight Leads)
• Current, Output: 500 mA
• Current, Supply: 10 mA
• Package Type: TO-220
• Regulation, Line: 9.9 mV
• Regulation, Load: 3.3 mV
• Regulator Type: Positive Voltage Out
• Resistance, Thermal, Junction To Case: 3 °C/W
• Temperature, Operating, Range: -40 to +125 °C
• Voltage, Input: 26 V
• Voltage, Noise: 99 μV
• Voltage, Output: 3.3 V
• Voltage Regulator Type: Linear
• Topology: LDO
• Regulator Output Type: Fixed
• Polarity Type: Positive
• Number Of Outputs: Single
• Input Voltage (min): 4.75V
• Input Voltage (max): 26V
• Output Voltage: 3.3V
• Output Current: 500mA
• Load Regulation: 3.3mV
• Line Regulation: 9.9mV
• Output Voltage Accuracy: ±5%
• Operating Temp Range: -40C to 125C
• Operating Temperature Classification: Automotive
• Pin Count: 3 +Tab
• Mounting: Through Hole
• Polarity: Positive
• Input Voltage Max: 26 V
• Output Type: Fixed
• Voltage Regulation Accuracy: +/- 5 %
• Maximum Operating Temperature: + 125 C
• Mounting Style: Through Hole
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Limit (min): -
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device
• Other names: *LM2937ET-3.3; *LM2937ET-3.3/NOPB; LM2937ET-3.3

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 4. Maximum Power Dissipation vs T
FIGURE 3. θ
is specified numerically by the heatsink manufacturer
(J−A)
the TO-263 Package
(H−A)
TO-263 Package
vs Copper (1 ounce) Area for the
is found using the equation shown,
(J−A)
(Continued)
is 35˚C/W and the maxi-
(J−A)
10011320
10011321
for the TO-263
AMB
for
(J−A)
9
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-
age.
FIGURE 6. Maximum Power Dissipation vs T
FIGURE 5. θ
(J−A)
the SOT-223 Package
SOT-223 Package
vs Copper (2 ounce) Area for the
(J−A)
of 74˚C/W for 1 ounce
10011322
10011323
www.national.com
AMB
for