TMP117: SDA fall time

Oba

Genius 17325 points

Part Number: TMP117

Hello,

My customer has an question for TMP117.

The datasheet specifies MIN of SDA fall time as 20 x (V+ / 5.5) nsec.
If V+ is 5V, it is 20 x 5 / 5.5 = 18.18nsec.

My customer measured this parameter of their own board and found it was about 12.52nsec.
The bit rate is about 150KHz.

I think the datasheet value just comes from I2C specification for FAST mode(400Kbps).

Is this 12.52nsec problem for 150KHz operation?

Regards,
Oba

over 4 years ago

0 Josh Wyatt over 4 years ago

TI__Guru* 91206 points

Oba -

Technically 150kHz is within fast mode I2C specification column. How did they measure this? Do you have an o'scope capture to share? - was it according to Figure 38 of the I2C spec, where tf is measured between 70% and 30% of the falling edge?

0 Oba over 4 years ago in reply to Josh Wyatt

TI__Genius 17325 points

Hello Josh,

I have sent the waveform in separated E-Mail.
What do you think about this waveform?
I think the waveform is clean. So I guess faster than specification with clean waveform doesn't cause any problem actually.

Regards,
Oba

0 Josh Wyatt over 4 years ago in reply to Oba

TI__Guru* 91206 points

Oba -

I think you are correct.

Sensors

Sensors forum

TMP117: SDA fall time