TMP102:I2Cデバイスの遮断処理について

MINORU YOSHIDA

Part Number: TMP102

スレーブアドレスに複数デバイスが接続されている場合で
そのうちの一つのデバイスの電源がOFFされた場合、他に接続されたデバイスがONの時、OFFされたデバイスの影響で
他のデバイスアクセスができないことが想定されますが、オープンドレイン出力同士の仕様なので、OFFしているデバイス側がLに引っ張って、他のデバイスアクセスができない、OFFされたデバイスが破壊するなどが懸念されますが通常、どのような回路処理を施す必要がありますか?TMP102Aセンサーの温度をOFFして使う予定がありますが
SWなどを挟んで、バスから切り離ししておく必要はあります?でしょうか?TS5A2066DCUなどを用いる必要がありますでしょうか?

3.3V仕様で使用する予定です。

アナログSWを用いない場合、OFFされたデバイスの端子のSCL、SDA端子は不定で
Lに張り付いてしまうことがあると考えています。

こちらへの回答をお願い致します。

over 3 years ago

0 Josh Wyatt over 3 years ago

TI__Guru* 91206 points

Dear Yoshi -

For the benefit of my team, as they may not be familiar with Japanese - Is this an accurate translation of your post above?

(In the future, on this Forum, please use English for all communications)

TMP102: I2C device shutdown processing

Even if multiple devices are connected to the slave address, If the power of one of the devices is turned off, 
when the other connected devices are turned on, the effect of the turned off device 
It is assumed that other devices cannot be accessed, but since it is a specification between open-drain outputs, there is concern 
that the device that is turned off will be pulled to L, making it impossible to access other devices, or that the 
device that is turned off will be destroyed. What kind of circuit processing do you usually need to do? 

I plan to use the TMP102A sensor with the temperature turned off. 
Is it necessary to separate it from the bus by inserting a switch or the like? 
Is it necessary to use the TS5A2066DCU or the like? 
I plan to use it with the 3.3V specification. 
If the analog switch is not used, the SCL and SDA pins of the turned off device are undefined. 
I think that it may stick to L. 

Please reply here.

0 MINORU YOSHIDA over 3 years ago in reply to Josh Wyatt

Prodigy 30 points

お世話になります。
ほぼ正しい翻訳
電源が切れたデバイスの破壊、または他の
通常のデバイスのI2C通信がオフデバイスの効果によって妨げられているかどうかを知りたいのですが。
気になる点があれば、なぜそうなのか、アナログSWなど、カットオフ回路を設け
るべきでしょうか?

0 Josh Wyatt over 3 years ago in reply to MINORU YOSHIDA

TI__Guru* 91206 points

Dear Yoshida -

Again, please reply in English - here is translation of your reply (from Google Translate)

Thank you for your help.
almost correct translation
Destruction of a powered down device or other
I would like to know if normal device I2C communication is hampered by off-device effects.
If there is something that bothers you, why is that so?
should it?

==============
I will go ahead and answer you here that the I2C protocol and systems are such that devices, if made correctly, 
will not answer or interfere with the bus when powered down. 

I have seen devices from other vendors that are back powered by the SDA and SCL voltages, and will respond to 
addressed commands, despite being disconnected from supply voltages.
The last one i can remember crossing paths with was a sensor from Renesas, however, industry wide, this is very rare
and the TMP102 has no reports of issues like that.

if you encounter any actual issues with the TMP102, please do come back to this forum, and please remember that we use 
the English language communicate here.

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TMP102:I2Cデバイスの遮断処理について