LM75A: Conversion time and SCL freq

Sunney Kumar

Part Number: LM75A

Hi,

In LM75A datasheet, t conversion time is mentioned as 100ms to 300ms with a note that specifies that LM75A should not be accessed continuously with a wait time of less than 300ms. As if it happens, the conversion that in progress will be interrupted.

Although during implementation, the access time interval is ~10ms.

Do you see a problem in that.

Regards,

Sunney

over 1 year ago

0 Eddie LaCost over 1 year ago

TI__Mastermind 39130 points

Hello Sunney,

Per the datasheet, this would be a violation of the spec, but also could have more serious implications for your use case. Different I2C devices will either NAK, no response, or respond with the previous measurement data when requested during a conversion. The TMP75A specifies that when accessed during a conversion, the "in progress" conversion will be interrupted and restarted at the end of communication. In order to avoid this condition, you must wait 1 conversion cycle(300ms) before the next I2C communication.

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0 Sunney Kumar over 1 year ago in reply to Eddie LaCost

Prodigy 60 points

Thank you for your response Eddie.

I have one more question regarding the digital spec.

Is clock period unit a typo error here? and what about other timing parameters units.

Regards,

Sunney

0 Jesse Baker over 1 year ago in reply to Sunney Kumar

TI__Expert 6830 points

Hi Sunney,

Yes it is a typo. The clock period should be 2.5uSec instead of 2.5nSec. 2.5 uSec is equal to 400kHz.

The other timing parameter units are correct.

Best regards,

Jesse

0 Sunney Kumar over 1 year ago in reply to Jesse Baker

Prodigy 60 points

Thank you Jesse

0 Sunney Kumar over 1 year ago in reply to Jesse Baker

Prodigy 60 points

Hi Jesse,

I have one more doubt.

In the design the I2C CLK frequency is used as 641KHz which is more than the LM75A specification. and design is working fine .

Is it possible that the I2C clock for this part can be more than 400kHz? if yes can you please let me know the upper limit.

Regards,

Sunney

0 Jesse Baker over 1 year ago in reply to Sunney Kumar

TI__Expert 6830 points

Hi Sunney,

The LM75A datasheet specifies I2C operation up to 400kHz. Although the design may be working fine, we cannot guarantee operation outside of what is shown in the datasheet.

Best regards,

Jesse

0 Sunney Kumar over 1 year ago in reply to Jesse Baker

Prodigy 60 points

Ok thank you Jesse for quick response.

regards,

Sunney

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LM75A: Conversion time and SCL freq