pin out for LM340-N of TO-220

Mark Liang

Intellectual 740 points

Other Parts Discussed in Thread: LM340, LM317-N

Hello,

Could you let us know what are the pinout for TO-220 of LM340-N? The information is not in the datasheet.

Best regards,

Mark

over 9 years ago

0 GJ over 9 years ago

TI__Intellectual 1106 points

Please refer to datasheet of lm7805c for the to-220 pin out.

We are in process of revamping the datasheets.

Regret the confusion.

0 Mark Liang over 9 years ago in reply to GJ

Intellectual 740 points

What are the difference between LM78xx and LM340-N, say LM7815C and LM340T-15? We are having a new design, should we use LM7815C or LM340T-15?

Best regards,
Mark

0 GJ over 9 years ago in reply to Mark Liang

TI__Intellectual 1106 points

Mark,

the top side mark on the device reads both LM340 and 7815

you could buy either of them. they exist due to historical reasons as two separate parts.

0 Mark Liang over 9 years ago in reply to GJ

Intellectual 740 points

So are they have the same die, or using the same technology?

Best regards,

Mark

0 GJ over 9 years ago in reply to Mark Liang

TI__Intellectual 1106 points

its the same part. we just have two orderables. whatever you order, you get the same part.

GJ

0 Mark Liang over 9 years ago in reply to GJ

Intellectual 740 points

What is the θcs for TO-220 for LM340T15/7815?

Best regards,
Mark

0 Michael_DeSando over 9 years ago in reply to Mark Liang

TI__Genius 12630 points

The available thermal information for LM340AT-5.0 for the TO-220 package (NDE) is

Theta JA-High K (standard datasheet value) 23.9 C/W
Theta JC, top (standard datasheet value) 16.7 C/W
Theta JB (standard datasheet value) 5.3 C/W
Psi JT (standard datasheet value) 3.2 C/W
Psi JB (standard datasheet value) 5.3 C/W
Theta JC, bottom (standard datasheet value) 1.7 C/W

Does this help? I am not sure we have data on Theta CS

0 Mark Liang over 9 years ago in reply to Michael_DeSando

Intellectual 740 points

Hi Michael,

We need to calculate Theta heat sink using:

Pdmax= (Tjmax -Ta)/(Theta heat-sink + Theta case-to-heat sink + Theta junction-to-case)

We have every values except Theta case-to-heat sink.

Do you know if there any way to calculate Theta heat-sink?

By the way, the datasheet states Theta junction-to-case = 4 degree C/W for TO-220 on page 2. Where the Theta JC = 1.7 C/W from?

Best regards,

Mark

0 Donald Jones over 9 years ago in reply to Mark Liang

TI__Mastermind 22610 points

The 'case to heat-sink' interface is your choice: Thermal grease; Thermal Epoxy, Sil-Pad, etc.

Check Section 2.8 on page 4 of the TI Design Guide : Thermal Design Guide for KeyStone Devices (Literature # SPRABI3)

Theta-cs or case to heat sink thermal resistance can be approximated using the following formula: 

CS = T / (k * A)

Where:

T = The thickness of interface layer between package and heat sink

k = The bulk thermal conductivity of the thermal interface material

A = The area over which the thermal interface material is applied

0 Michael_DeSando over 9 years ago in reply to Mark Liang

TI__Genius 12630 points

Hello Mark,

Sorry for the confusion on the difference in values. We are currently updating the LM340-N/LM78XX datasheet and the numbers I provided are from our latest thermal models. To see an updated datasheet for thermal information on a similar part with the same package, refer to the following datasheet for LM317-N www.ti.com/.../lm117.pdf

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pin out for LM340-N of TO-220