TMP464: transistor difference between TMP461 and TMP464

Toshihiro Watanabe

Genius 10235 points

Part Number: TMP464
Other Parts Discussed in Thread: TMP461, , TMP468EVM

Hello,

In 8 Application and Implementation, below transistors are recommended.

TMP461: 2N3904 (NPN) or 2N3906 (PNP)

TMP464: MMBT3904 (NPN) or a MMBT3906 (PNP)

Is there any difference between them?

Are they N-factor 1.008? If yes, is it ok we can get the datasheet accuracy without any register write?

Best regards,

Toshihiro Watanabe

over 5 years ago

0 Brandon Fisher94 over 5 years ago

TI__Mastermind 27555 points

Hi Toshihiro-san,

The difference between MMBT390x and the 2N390x standard transistors is the package. All of the 2N390x transistors I have seen are in through-hole TO-92 packages, and all of the MMBT90x transistors I've seen have been in SOT-23style packages.

Unfortunately the N-factor of any given transistor can vary a lot depending on vendor. For example, the transistors on the TMP468EVM are MMBT3904s but have an ideality constant very close to 1. This is why we can only guarantee accuracy for transistors with N-factors of 1.008, and not for any specific transistor type.

Best Regards,
Brandon Fisher

0 Toshihiro Watanabe over 5 years ago in reply to Brandon Fisher94

TI__Genius 10235 points

Hello Brandon-san,
MMBT3904s N-factor is almost 1. We can use MMBT3904s to understand N factor is different,has some error?
Best regards,
Toshihiro Watanabe

0 Brandon Fisher94 over 5 years ago in reply to Toshihiro Watanabe

TI__Mastermind 27555 points

Hello Toshihiro-San,

Yes, you can use an MMBT3904 transistor that has an n-factor of 1 with the understanding that it will cause additional error. This additional error can be a few degrees though, section 8.2.1 of the TMP464 datasheet shows how to estimate it. At 100°C for an n-factor of 1, the additional error can be around 3 °C.

Best Regards,
Brandon Fisher

0 Toshihiro Watanabe over 5 years ago in reply to Brandon Fisher94

TI__Genius 10235 points

Hello Brandon-san,

Thank you for your support. Is it no issue if we use TMP461+MMBT390x conbination because MMBT390x and 2N390x N factor is almost same (around 1)?

Best regards,

Toshihro Watanabe

0 Brandon Fisher94 over 5 years ago in reply to Toshihiro Watanabe

TI__Mastermind 27555 points

Hi Toshihiro-San,

Yes, you can use either the MMBT390X or the 2N390X with the TMP461. The N-factor of these transistors may not be around 1 though, since it depends on manufacturer.

MMBT390X transistors may have different N-factors if they are from different manufacturers as well. Unfortunately we don't know what the n-factor will be for any transistor that is selected.

Best Regards,
Brandon Fisher

0 Toshihiro Watanabe over 5 years ago in reply to Brandon Fisher94

TI__Genius 10235 points

Hello Brandon-san,

I can undestand N factor may be different if manufacture is different. But there is a discussion MMBT390X N factor is almost 1. What is the manufacture?

It seems there are many vendor makes the same part name. We would like to use known (N factor =1) device.

Best regards,

Toshihiro Watanabe

0 Brandon Fisher94 over 5 years ago in reply to Toshihiro Watanabe

TI__Mastermind 27555 points

Hi Toshihiro-San,

Here is the information for the transistors used in the TMP468EVM, the manufacturer we used is Diodes Inc.

Best Regards,
Brandon Fisher

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TMP464: transistor difference between TMP461 and TMP464